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PICList Thread
'[ee OT]Kynar motion'
1999\08\05@173646 by Anne Ogborn

flavicon
face
> one wall of the bag could be Kynar (Piezo Co-Polymer)plastic that
> will bend when energized (very low power) this will eject the fluid
> into the main body of reacting fluid, a chemical process will take
> place and the internal temp is monitored until another "dose" is
> needed.
> The other unopened bags could even act as a stirring source since
> their respective piezo linings could act together in a synergesis of
> stirring.
> I have experimented with Kynar... it will do this.

How about some details of where to get Kynar film, how to
attach electrodes, etc. to demonstrate this effect?
This sounds like a way cool thing to know about.

Oh, and as for my subject line - I've labelled it [ee OT] since it
seems we have 3 catagories of subject - 1. Stuff directly related to PIC,
2. Stuff related to robots, electrical gizmos, robots, and other stuff
a PIC'ish person might be interested in, 3. general 'commmunity' discussion
(the how many pics to save JFK thing)  I'm experimenting with labelling
catagory 2 topics [ee OT] since 'electrical engineering' seems as
close to describing it as anything.

--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

1999\08\05@180134 by l.allen

picon face
> How about some details of where to get Kynar film, how to
> attach electrodes, etc. to demonstrate this effect?
> This sounds like a way cool thing to know about.
>

Kynar is available from AMP Inc (the big connector makers)
The only address I have here is Valley Forge P.A.
Kynar is a Piezo Film that can be used for hydrophones (my main use),
speakers (above 2kHz), contact microphones, pyro sensing (.. very
good IR detectors) and very high reliability/cycle life switches
(dynamic only though, not absolute).. Gottlieb use it in Pinball
Machines now.
Electodes are vapour deposited on the material so can either be
inserted in a pressure contact or a type of rivet attached to it.
The AMP Basic Design Kit for Piezo Film Sensors is a great start,
with many samples, applications etc.
Quite a range of off the shelf sensors/transducers in various form
factors are available from AMP.

I should be on their sales team.

Oiii... where's my commission.


_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand
_____________________________


'[OT] What is a Sigma-Delta AtoD converter? [EE]'
2000\04\12@115610 by Mark Skeels
picon face
Hi, folks.

TelCom has a new AtoD part, a TC3401. It claims to be a 16 bit AtoD
converter and it's cost at 1000 pcs is $4.63 US.

I never heard of a Sigma-Delta AtoD converter before. Can anyone tell me how
it works, and has anyone had experience with this new part?

Thanks on advance,

Mark

2000\04\12@121456 by Wagner Lipnharski

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All ADCs for high bit counting (bigger than 14 bits) use Sigma-Delta
conversion for a lower cost production. Sigma Delta use a capacitor ramp
measurement based on voltage comparison. They use integration, discharge
and other techniques to get great precision and accuracy. Actually they
are quire precise, and much cheaper than the regular instantaneous
multiple voltage comparison technique used in lower bit count.

Personal experiences about ADC's point the latest Linear Technologies
LT2400 and LT2408 one of the easier to use, with a low cost. They run at
24 bits !!! in just 8 pin DIP package for the 2400.  The 2408 has an
embebed input mux at the chip.

Wagner.

Mark Skeels wrote:
{Quote hidden}

2000\04\12@175622 by Plunkett, Dennis

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I don't agree to this reasoning,
A sigma delta converter is different to how one might expect that they work.
The sigma part is an intergration point of the converter. This is used to
only reduce the delta of the incomming signal so that a simple comparator
can be used in the desission process (Have a look at stuff on one bit DSP).
The great thing about this style of converter is that the noise is high pass
filtered by nature of design. The basic concept of sigma (intregation) delta
(Change in) has been around since the 1950's but only in recent times has it
been of use.


Dennis





> {Original Message removed}

2000\04\12@195548 by Brandon, Tom

flavicon
picon face
www.dspguide.com/ has the full text to the Scientist's And Engineer's
Guide to DSP. Chapter 4 (ADC And DAC) has a nice low-maths explanation of
how they work.

Wagner's quite right, except I believe that you will still find a few
high(ish) accuracy non sigma delta converters as sigma delta converters
aren't very appropriate for time domain encoded information (e.g. any form
of echo location system (sonar, radar et al)). Sigma delta converters (sigma
= sum, delta = change = sum of changes converter) produce a value that
represents the AVERAGE voltage in the conversion period (or average slope of
voltage (not commercially used I don't think)) rather than the instantaneous
voltage at a known point in the conversion process. i.e. in a 1kHz SD
converter you'd know the average coltage for each 1ms period. This is fine
for frequency encoded signals such as audio but if you need to know the
shape of a wave then they're not especially suitable.

Tom.
{Original Message removed}

2000\04\12@205218 by Plunkett, Dennis

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> Wagner's quite right, except I believe that you will still find a few
> high(ish) accuracy non sigma delta converters as sigma delta converters
> aren't very appropriate for time domain encoded information (e.g. any form
> of echo location system (sonar, radar et al)). Sigma delta converters
> (sigma
> = sum, delta = change = sum of changes converter) produce a value that
> represents the AVERAGE voltage in the conversion period (or average slope
> of
> voltage (not commercially used I don't think))
>
       I think that this is a dual slope style converter that your are
thinking of
       Sigma is to integrate. This is done in the front end
       of the converter so that the rate of change in the incomming signal
is reduced, so then the delta area can run
       at a lower speed so as to produce a small rate of change in period,
it is then the period of the rate of change of the output multiplied by the
sigma value that then represents the actual input value.

       A simple signal delta converter of this type can be represented as
the following:-

       input-------> sigma--------------Comparator----------->output

       (forgive the ASCII art)


> rather than the instantaneous
> voltage at a known point in the conversion process. i.e. in a 1kHz SD
> converter you'd know the average coltage for each 1ms period.
>
       OK you are talking about averaging here so I do think that the
converter you are looking at is a dual slope type, and is good for removing
CMR.

>  This is fine for frequency encoded signals such as audio but if you need
> to know the
> shape of a wave then they're not especially suitable
       Only for slope converters, else my current DSP project would not be
working :), else we  would also have to come up with a valid explanation as
to why Sigma Delata converters are used in the French radar system and in
the Australian Jindalee over  the horizon radar


       Dennis





> Tom.
> {Original Message removed}

2000\04\13@045257 by Alan B Pearce

face picon face
>The basic concept of sigma (intregation) delta
>(Change in) has been around since the 1950's but only in recent times has it
>been of use.

I believe the early digital telephone a/d converters were sigma delta types as
it was possible to do the u-law or A-law encoding directly in the a/d converter
by changing the delta size as the digital value changed. This saved doing a high
precision a/d conversion and then doing a conversion to the A-law or u-law
value. I think you will find these converters have actually been in commercial
use longer than you think.

'pcb engraver & circuit layout site [OT] [EE]'
2000\04\13@090730 by Arthur

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face
Hi all
found this site which as a few demo programs that may be of intrest.

all the best Art

spam_OUTartbTakeThisOuTspamcableinet.co.uk
.....wildKILLspamspam@spam@blueyonder.co.uk

'pcb engraver & circuit layout site [OT] [EE] repos'
2000\04\13@134811 by Arthur

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face
Hi all
rposting this as url missed
found this site which as a few demo programs that may be of intrest.

http://www.merco.nl/

all the best Art

artbspamKILLspamcableinet.co.uk
.....wildKILLspamspam.....blueyonder.co.uk

'[OT][EE]{WKB] Speedwire Prototyping system--lookin'
2000\04\14@191917 by William K. Borsum

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face
<x-flowed>At 09:02 AM 4/14/00 , you wrote:
>Hello Kelly,
>Saw your posting regarding about "stitch wireing" (IIRC), I have been
>doing quite a searching but could not find a URL that describe this in
>details, nor could find the BICC-Vero web-site.
>Do you some URL to point me to?
>Cheers,  Ling SM

Ah yes--They changed their name.  In the U.S. it is now VERO Electronics,
1-800-242-2863.  <EraseMEwww.verospam_OUTspamTakeThisOuTvero-usa.com">http://www.verospamspam_OUTvero-usa.com> it says on the catalog.  Company
is British, and home page should be <http://www.vero-uk.com>.

Absolutely fantastical system for prototyping through-hole parts! Beats
wire wrap all to H.  Rip-up & retry is very easy.  I've even got some small
proto-cards set up with 8-SOIC pads plus holes.  Coat the wired side with
silicone rubber and I have even delivered one-ups to customers.  Super
system  Just need a reasonably priced source for the pins.

The product is called "Speedwire" and is on page 8-27 of their catalog.
The terminals are part #244-26219J in reels of 1000 pieces.
The tool is #244-26213E and I would recommend getting two of them
Don't bother with their installation tool--a pair of pliers works better.
ANY 30 ga Kynar wire wrap wire will work.
I buy blank PCB material with 62mil holes on 100 mil centers from
Mouser--lots cheaper.

The cost is about $250/reel in the U.S (competitive with better quality IC
sockets on a per pin basis)--plus long lead times.  I'd would be willing to
buy a couple of reels from a piclister in the UK if there is a significant
price savings.

Kelly



William K. Borsum, P.E. -- OEM Dataloggers and Instrumentation Systems
<@spam@borsumKILLspamspamdascor.com> & <http://www.dascor.com>San Diego, California, USA

</x-flowed>

'[OT] What is a Sigma-Delta AtoD converter? [EE]'
2000\04\14@203454 by Russell McMahon

picon face
>I never heard of a Sigma-Delta AtoD converter before. Can anyone tell me
how
>it works, and has anyone had experience with this new part?

I am using a software implemented Sigma Delta converter in a current project
(using a Z8 :-))


The SD converter is essentially a tracking integrator.

A comparator is used to compare the input voltage with the voltage on a
capacitor.
Once per clock cycle, if the capacitor voltage is lower than the input then
a positive drive signal is applied via a resistor to the capacitor. If the
capacitor voltage is too high a negative drive signal is applied. The drive
signal continues for the rest of the clock cycle EVEN IF THE COMPARATOR
CHANGES STATE BEFORE THE END OF THE CYCLE. The relative number of highs and
lows of the driving signal allow one to calculate the value of the input
relative to the reference.

Using a Z8 with an internal comparator this essentially allows a converter
to be made with a reference, one capacitor and 2 resistors. In practice I
add 2 opamp sections before this to provide voltage gain and buffering.
Still a cheap and accurate converter. I get about 10 bits of accuracy but
more can be had with longer conversion times.



     Russell McMahon
_____________________________

- http://www.easttimor.com
      Updated regularly:
      100,000 refugees STILL in  West Timor face starvation!

- http://www.sudan.com
   And you think Kosovo and Chechnya are bad!

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))


{Original Message removed}

2000\04\15@165321 by Scott Dattalo

face
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On Sat, 15 Apr 2000, Russell McMahon wrote:

{Quote hidden}

I was wondering when you were going to chime in Russel.

A pic version of what Russel describes can be found here:

http://www.dattalo.com/technical/software/software.html

I know one person that's trying to use this. I won't mention names, but let's
say that she's pulling her hair out to get it to work.

The point being, there are subtleties with this circuit that aren't immediately
obvious. For one, the circuit has a relatively low input impedance compared to
most A/D converters.  In addition, the output impedance of the signal being
measured is assumed to be low.  But a buffer amplifier like Russel mentions can
fix both of these problems. Depending on the source, you could add a 'large'
capacitor - say 10 times the integrating one - instead of a buffer at the input
of this poor person's sigma-delta converter and some what alleviate problems
associated with high impedance signals.

Another caveat is that the R's and the C need to be tightly coupled with the
loop time of the software. If the RC time constant is too large you run the
risk of not being able to have the pic charge or discharge the capacitor during
a pass through the algorithm. If the RC time constant is too small then every
iteration through the algorithm would cause the digital input to switch
states. The values on my web page for the R and C are 10k and 0.56uF were the
result of convenience - I'm not sure if they're optimum.

Scott

2000\04\15@165731 by David VanHorn

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face
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1


>> I am using a software implemented Sigma Delta converter in a current
project
>> (using a Z8 :-))

>> Using a Z8 with an internal comparator this essentially allows a converter
>> to be made with a reference, one capacitor and 2 resistors. In practice I
>> add 2 opamp sections before this to provide voltage gain and buffering.
>> Still a cheap and accurate converter. I get about 10 bits of accuracy but
>> more can be had with longer conversion times.


I had a bad experience with one of these.  We were stepping a motor
(microstepping) and sampling, and the best we could get to was 6 bits at
7200s/s.
That /12 on the xtal is a real killer.

- --
Are you an ISP?  Tired of spam?
http://www.spamwhack.com  A pre-emptive strike against spam!

Where's Dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9

-----BEGIN PGP SIGNATURE-----
Version: PGPfreeware 6.5.2 for non-commercial use <http://www.pgp.com>

iQA/AwUBOPjxhYFlGDz1l6VWEQL+yQCg54R6E6BqaR7GtL6xybLJ2SkjpcMAoNKi
MRBl0i3cuqQjB5IA8d/0AZYB
=3o2B
-----END PGP SIGNATURE-----

'[OT] [EE] PCB Issues'
2000\04\17@105121 by Dan Michaels

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Related to various questions in recent weeks, regarding pcbs,
terminations, etc, I discovered Doug Brooks' articles online.
Some written for Printed Circuit Design mag.

http://www.ultracad.com/articles.htm

Articles on ground planes and a pcb with 2100 bypass caps (!!).

best regards,
- Dan Michaels
Oricom Technologies
http://www.sni.net/~oricom
==========================

'[OT] What is a Sigma-Delta AtoD converter? [EE]'
2000\04\17@131746 by Alice Campbell

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face
Guilty Party Replies:

Ha!! It's all true, what Scott says.  Spent about 3 weeks
getting the silly thing to work, it finally worked sunday at
about noon.  And i still have 1 hair left.

Last thursday, Scott told me that i might have an impedance
problem, and suggested a cap beneath the pot to match
impedance.  Didnt work.  But it gave me an idea, so i dropped
the pot like a hot potato and put in a cheesy old lm358 from
the junk pile.  Fearing to fry my new pin photodiode, i put
in a reverse-biased led and 4M of feedback and VOILA! it
works.  AND i used tris on the ports, both on 16F84 and
16F877.

And try as i might, a pot just doesnt seem to work well in
this circuit.  When i get a chance, i will investigate
further, but i have not been successful in getting it to read
a pot.  It really likes to work with an opamp.  I agree that
the r-c constant for the main A2D is important, but it's more
important that any stabilizing cap on the output of the opamp
be a couple of orders of magnitude bigger than the one used
by the ADC.  The software can handle down to .01 uF caps at 4
MHz, but i wouldnt try such a small cap at 32kHz--well, maybe
i might try it later, just to confirm suspicion.  And i used
a mylar film cap for the A2D, no way after all that work will
i use leaky old caps.

Wheeeeeeeeeeeeeeeeeeeeeeee-Haa

alice

{Quote hidden}

2000\04\17@134838 by jamesnewton

face picon face
Can you post a quick schematic and the code? Or is this a commercial thing?

---
James Newton KILLspamjamesnewtonKILLspamspamgeocities.com 1-619-652-0593
http://techref.massmind.org NEW! FINALLY A REAL NAME!
Members can add private/public comments/pages ($0 TANSTAAFL web hosting)


{Original Message removed}

2000\04\17@142644 by Alice Campbell

flavicon
face
OK, since you asked.  BUT this is still interim code, i have
not yet tested the 2-wire routine.  Instead of testing it all
afternoon yesterday i dug up the garden and planted tomatoes.
And took the night off.

schematic & code is waaaaay down at bottom.

{Quote hidden}

;       mostly by Scott, the fiddly stuff by alice 4/00
     list    p=16F84,t=ON,c=132,n=80,st=off
      __CONFIG   _CP_OFF & _WDT_OFF & _PWRTE_ON & _XT_OSC
       include "P16F84.INC"
;;      list    p=16F877
;;      __CONFIG   _CP_OFF & _WDT_OFF & _RC_OSC &_LVP_OFF
;;      include "P16F877.INC"
 cblock   0x0C
   count
   t1,t2,freq
   error_code
   total_lo,total_hi
   count_lo,count_hi
 endc
out_port        =       PORTB;PORTC
A2D_PORT        EQU     PORTA
A2D_IN_BIT      EQU     0
A2D_OUT_BIT     EQU     1
ERROR_STUCK_HI  EQU     .255
ERROR_STUCK_LO  EQU     2
beep_pin        equ     3
;          pot
;+5V __/\/\/\/\__ gnd
;          ^
;          |                 +---------------- pic input
;          |        10K      |       10k
;          +------/\/\/\/\---+----/\/\/\/\---- pic output
;          |                 |
;         === 100u          === .1 to 1u
;          |                 |
;         gnd               gnd
;
;The big 100u (or bigger if you want) cap will provide a low impedance
;voltage source.  This runs at 4 MHz.
;-----------------------------------------------------------
       nop
       ORG     0               ;Reset Vector
       ORG     4               ;Interrupt Vector
restart
;;      bcf     STATUS,RP1
;;      BCF     STATUS,RP0
       CLRF    A2D_PORT
       bsf     STATUS,RP0
       CLRF    out_port
       movlw   b'00000001'
       movwf   A2D_PORT
;;   movlw   b'00000110'
;;   movwf   ADCON1
       bcf     STATUS,RP0
       CLRF    A2D_PORT
       clrf    error_code
start:
loop:
       clrf    count_lo
       clrf    count_hi
       call    a2d_convert2
;       movfw   count_lo        ;varying pitch
;       call    beep            ;using squeeker
      movfw   count_lo         ;in lights
      movwf   out_port         ;on board
       call    big_delay
       call    big_delay
       CLRF    A2D_PORT
       clrf    error_code
       goto    loop
;--------------------------------------------------------
;a2dconvert
;
; 2I/O pins
a2d_convert:
       call    precharge
a2d_loop
       RLF     A2D_PORT,W        ;roll it in
      andlw   b'00000010'       ;isolate it  so it wont screw up the other buttons
      xorwf   A2D_PORT,F        ;flip it
       clrc
       movlw   1
       btfss   A2D_PORT,A2D_OUT_BIT
        addwf  count_lo,f
       skpnc
        addwf  count_hi,f
       addwf   total_lo,f
       skpnc
        addwf  total_hi,f
     clrf    t1        ;SLOW DOWN SPIKES
     decfsz  t1,f
     goto   $-1
       btfss   total_hi,0;4
        goto   a2d_loop
       return
;--------------------------------------------------------
; precharge
precharge:
       movlw   1
       clrf    total_lo
       clrf    total_hi
       bcf     A2D_PORT,A2D_OUT_BIT
   ; Make the capacitor voltage go below the trip threshold
pc_low_loop
       btfss   A2D_PORT,A2D_IN_BIT
        goto   pc_high
       addwf   total_lo,f
       skpnc
        addwf  total_hi,f
;;      btfss   total_hi,0
       skpc
        goto   pc_low_loop
       movlw   ERROR_STUCK_HI
       movwf   error_code
       goto    display_error
   ; Now make the capacitor voltage go above the trip threshold
pc_high:
       BSF     A2D_PORT,A2D_OUT_BIT
       clrf    total_lo
       clrf    total_hi
pc_high_loop:
       btfsc   A2D_PORT,A2D_IN_BIT
        goto   precharged
       addwf   total_lo,f
       skpnc
        addwf  total_hi,f
;;      btfss   total_hi,0
       skpc
        goto   pc_high_loop
       movlw   ERROR_STUCK_LO
       movwf   error_code
       goto    display_error
precharged:
       clrf    total_lo
       clrf    total_hi
       bcf     A2D_PORT,A2D_OUT_BIT
       return
;-----------------------------------------------------------------
; a2d_convert
;
;1 I/O pin
a2d_convert2:
   ;Put the A2D_PORT's tris into the FSR so that we can
   ;access it with out having to do those damn bank selects
       movlw   TRISA
       movwf   FSR
       movlw   1
       clrf    count_lo
       clrf    count_hi
       clrf    total_lo
       clrf    total_hi
       clrf    t1
   ; Step 1 is the pre-charging cycle where the capacitor
   ;is made to pass through the low-to-high threshold and
   ;then again through the high-to-low threshold.
   ; This ensures that the voltage on the capacitor is the
   ;same for each time we pass through the algorithm.
   ;Make the capacitor go through the low to high threshold
       bsf     A2D_PORT,A2D_OUT_BIT
       bcf     INDF,A2D_OUT_BIT
a2d2_l1
       call    delay16
       call    delay16
       call    delay16
       call    delay16
       bsf     INDF,A2D_OUT_BIT
       call    delay16
       btfsc   A2D_PORT,A2D_OUT_BIT
        goto   a2d2_l2
       bsf     A2D_PORT,A2D_OUT_BIT
       bcf     INDF,A2D_OUT_BIT
       decfsz  t1,f
        goto   a2d2_l1
;       movlw   ERROR_STUCK_LO
;       movwf   error_code
;       goto    display_error
  ;now pass through the high to low threshold
a2d2_l2
       clrf    t1
       bcf     A2D_PORT,A2D_OUT_BIT
       bcf     INDF,A2D_OUT_BIT
a2d2_l3
       call    delay16
       call    delay16
       call    delay16
       call    delay16
       bsf     INDF,A2D_OUT_BIT
       call    delay16
       btfss   A2D_PORT,A2D_OUT_BIT
        goto   a2d2_l4
       bcf     A2D_PORT,A2D_OUT_BIT
       bcf     INDF,A2D_OUT_BIT
       decfsz  t1,f
        goto   a2d2_l3
;       movlw   ERROR_STUCK_HI
;       movwf   error_code
;       goto    display_error
a2d2_l4    ;If we get then we've successfully precharged the capacitor
   ;Also, the capacitor voltage is just below the high-to-low
   ;threshold (Vil) so let's begin by ramping it positive
       bsf     A2D_PORT,A2D_OUT_BIT
       bcf     INDF,A2D_OUT_BIT
a2d2_l5
       addwf   total_lo,f
       skpnc
        addwf  total_hi,f
       btfsc   total_hi,0
        return
       call    delay16
       call    delay16
       call    delay16
       call    delay16
       bsf     INDF,A2D_OUT_BIT
       call    delay4
       btfss   A2D_PORT,A2D_OUT_BIT
        goto   a2d2_low
       addwf   count_lo,F
       ;The cap voltage is too high
       bcf     A2D_PORT,A2D_OUT_BIT
       bcf     INDF,A2D_OUT_BIT
       skpnc
        addwf  count_hi,F
       goto    a2d2_l5
a2d2_low
       ;The cap voltage is too high
       bsf     A2D_PORT,A2D_OUT_BIT
       bcf     INDF,A2D_OUT_BIT
       goto    $+1
       goto    a2d2_l5
       return
;--------------------------------------------------------
;; error - write an error code to output device
display_error:
       bsf     STATUS,RP0
       clrf    out_port          ;Make portb i/o pins outputs
       bcf     STATUS,RP0
error_loop:
       movf    error_code,W
;       CALL    beep    ;if device is beeper
       movwf   out_port
;       skpz
;        goto   error_loop
       ;If the error code is zero, then flash the LEDs
      call    big_delay
;       comf    out_port,f      ;flasher
      call    big_delay
       GOTO    restart
       goto    error_loop
;----------------------------------------------------
big_delay:
       clrf    t1
       clrf    t2
       decfsz  t1,f
        goto   $-1
       decfsz  t2,f
        goto   $-3
       return
;------------------------------------------------------
delay16 NOP
delay15 NOP
delay14 NOP
delay13 NOP
delay12 NOP
delay11 NOP
delay10 NOP
delay9  NOP
delay8  NOP
delay7  NOP
delay6  NOP
delay5  NOP
delay4
       RETURN
;------------------------------------------------------
beep                            ;normally assumes freq is in work
;       movfw   count_lo        ;freq proportional to answer
       movwf   freq            ; get frequency
       movlw   .25
       movwf   t1              ;shorten up loop for simulator
;       clrf    t1
       clrwdt
beeploop
       movfw   freq
       movwf   t2
       bsf     A2D_PORT,beep_pin
        clrwdt
        movlw   b'00001000'     ;beeper is on porta,3.
        xorwf   A2D_PORT,f
        decfsz t2,f
        goto   $-4
       decfsz     t1,f
       goto    beeploop
       return
;------------------------------------------------------------------
;-------------------------------------------------------
       END
;==========================================================

2000\04\17@153125 by Dan Michaels

flavicon
face
At 10:47 AM 4/17/00 -0700, you wrote:
>Can you post a quick schematic and the code? Or is this a commercial thing?
>

You might check this out too: "Care and Feeding of the 1-Bit DAC"

http://www.ee.washington.edu/conselec/CE/kuhn/onebit/primer.htm

2000\04\17@171137 by Walter Banks

picon face
----------
> From: Alice Campbell <spamBeGone1502amcspamBeGonespamLO.SCSENG.COM>

> And try as i might, a pot just doesnt seem to work well in
> this circuit.  When i get a chance, i will investigate
> further, but i have not been successful in getting it to read
> a pot.  It really likes to work with an opamp.

The opamp isolates the circuit from the pot.
When you are using a pot as a reference then you
need to account for the fact that the output
impedance of the pot varies with voltage.

As Scott said the input impedance is quite low
but we and many of our customers have used this
in commercial products.

Walter Banks

'ATX power suply - very [OT][EE]'
2000\04\18@091450 by Arthur

flavicon
face
Paul B. Webster wrote:

I'd be interested (as may many of the list) to know what you find, and
what you intend to do.  One detail I have figured is that motherboards in
general default OFF.  If however you short the front panel button,
they default ON but of course you can't turn them off then.
______________________________

Paul
one way to do this is to use a 10u Cap across the switch input to the board
with a diode cathode  to +5 volts to discharge cap at switch off.
then when machine is switched ON cap acts like short and pc starts up.
But my bios for a new mother board I'am using now lets me select switch mode
as options instant off. delayed off and machine to start when power is
applied.

'[OT] [EE] 24-bit A/D. Are We in the Twilite Zone H'
2000\04\24@165527 by Dan Michaels

flavicon
face
Wagner wrote:
.....
>I use Max641, 586 or 587 at my devices (the first one has an internal
>catch diode). EMI? yes, but not enough to cause any problems at the 22.5
>bits ADC installed less than 20 mm from the coil.  Just for info, this
>ADC resolution is about 0.12uV (120 nano Volts), the interference should
>exist but it is not noticeable.
>

Yeah, 0.12 uV. 22.5 bits. Right.

Wagner, I noticed your mention of using the LTC2400 a couple of weeks
ago, and downloaded the datasheet. I'm still digesting it. I've built
amps for amplifying 2-5 uV before, and it's not all that easy to get
good results at those levels. Now, you and Linear Tech come along and
say, hey, we got 0.12 uV sensitivity here, and it works with a buck
regulator ckt, too. Oy, yoy, yoy.

I've got one board with opAmps and a 12-bit LTC1400 running up to
400 Ksps [with 20 Mhz PIC on-board, of course], and damn if I can
get the noise level below about 2 mV, no matter what I do. I've
read everything ever written on low-noise analog and high-speed
digital design, and tried 100 different things, and it's still
2 mV [that's **MILLI-volts**].

On a thread a few weeks ago, I asked a simple question of someone
about how they got their Vref to be noise-free at 12-bits, got
no response back from that guy, but did get some other clowns
telling me "... seems some people are re-learning things the hard
way ...." and ".... yes folks ohm's law is a reality ...", or
some such blather.

Forget the switcher. 0.12 uV. And with digital circuitry within
200 *yards*. Are you kidding?

I realize that the LTC2400 has differential input and 3 hz
bandwidth, etc/etc, whereas I have single-ended input, opamp ckt
with Rin = 1M and BW = 1 Mhz, plus A/D SPI running at 6.4 Mhz,
but still -- 2 mV noise. What's a poor fella to do? [beyond the
100 things he's already tried].

Am I at the tradeoff point in my design? Is there some magical
Noise-vs-??something??  formula here I forgot about [like trading
gain for bandwidth]? Also, they are putting 16-bit sound cards
into PCs nowadays. What the heck do those guys know, that they
can accomplish that?

Cheers,
- Dan Michaels
Oricom Technologies
===================

2000\04\24@175950 by dal wheeler

flavicon
face
Along these lines (minus the head butting), what are people actually *doing*
to compensate for the switcher noise when hooking up to analog circuitry.
Yes, I know it's better to avoid the issue and go with a linear supply, but
what have people done to "clean up" the analog portion when using a
switcher.

{Quote hidden}

2000\04\24@194816 by Wagner Lipnharski

flavicon
face
Well Dan, noise is a tricky thing.

Right now I am producing a pressure calibrator that uses the AD7713,
well, somehow extinct and replaced (supersede) by the AD7714, it is a
22.5 bits ADC, with 3 fully differential selectable inputs.  The
pressure transducer supply 100mV with the full scale pressure, but if I
supply the sensor bridge with 1/3 of its required constant current, it
gives me only around 32mV at full scale.  I am being reading 0.1PSI with
this 30PSI transducer, so it means around 100uV of analog signal, and
the 7713 is pretty steady and accurate.

The biggest problem I found years ago with low voltage is really noise
in voltage reference generators.  At this point I found out that in this
particular point "you have what you pay for".   The LM358 1.2 and 2.5V
reference has several versions, going from 91 cents up to $4.66
(30ppm/degC).  The LM4040 series are pretty good too, but you need to go
for a .1%, as the LM4040AIZ-2.5-ND (Digikey) for $4.10 per (TO-92)
unit.  The most important part of the tech specs of those vref's is the
"noise" part.  Some of them just obscure it, other just misinform, but
some state it. Some of them have milli-volts of noise (white noise,
pink, whatever), it is an intrinsic silicon noise, can't be removed,
can't be filtered, there is NO capacitor can avoid it, stabilize or
level it.  You just need to check the manufacturer document (specs
sheet) for the one you are using.  The above information is from
Digikey, you can get better products around.

Years ago I made a nice portable instrument, one of the functions were
to generate current and voltage, in micro-volts range.  I suffered like
hell trying to locate why the output voltage was so noisy. The output
was programmable from 0 to 25V in 10 micro-volts steps, so you could
specify 24.999,99 but the high precise HP unit I was using to measure it
always showed last two digits floating and jumping.  I changed
everything, from the solderless protoboard (first mistake), op-amps,
capacitors, resistors to 20ppm 0.1%, and so on.  Using a signal booster
I could see the vref noise. I was using a 1.25Vref, noise was in the
60uV range (according to the manufacturer), but the DAC was multiplying
by almost 20 times to get the 25V output, so the noise went up to almost
1.2mV!!! sometimes higher.

So I learned that there are two very, very important things in all
electronics... the bases... Clocks for digital and Vref's for analog.
They can cost up to 1/20 of the total equipment, now I recognize and pay
it with pleasure, they ARE what the product will offer as quality and
accuracy anyway.  Doesn't make sense to use a 91 cents Vref in a product
that cost $1500 to the customer, and that cheap Vref will define the
product accuracy and quality... you know what I mean.

I never thought to use a thermal oven for a crystal oscillator in life,
but I did once. It runs under 45¡C, needs 48 hours to stabilize before
calibration, and needs 4 calibrations, once each 6 hours after the
initial warm-up. Can't use a regular metallic screwdriver to touch the
cap inside the crystal chamber since it can change the internal temp...
and of course frequency, isn't that funny?  The plastic screwdriver
should be kept in another 45¡C chamber... scary. But when you go for
critical and high accurate things, there is no other way.

Calculations:   1.25Vref with 60uV of noise, means:

625mV  = 1 bits
312mV  = 2 bits
156mV  = 3 bits
78mV  = 4 bits
39mV  = 5 bits
19mV  = 6 bits
 9mV  = 7 bits
 4mV  = 8 bits
 2mV  = 9 bits
 1mV  = 10 bits
610uV  = 11 bits
305uV  = 12 bits
152uV  = 13 bits
76uV  = 14 bits
38uV  = 15 bits

So, the noise kills the unit at 14 bits, can't use it with a 16 bits ADC
or DAC.

Now, other thing. accuracy (percentage of error).
The LM4040 unit described above, has 0.1% or error. It means that in
1.25000V vref, it can be in real 1.249000 or 1.251000, now, if you look
at the above table, find the 1/1000 part, you will see the 1mV at 10
bits, so all above 10 bits will be not valid.

Now, look for ppm, a 30ppm/degC, means the unit will change its value in
30 parts per million per each celsius degree the ambient temperature
changes from the based 20¡C.  Then, suppose the room is at 25¡C, it will
be 150 parts per million, 150/1000000 or 0.00015, in other terms it is
0.015%, pretty high for only 5¡C in change, it is 0.003% per ¡C.  The
original 1.250000 V will change to 1.249250 V at zero ¡C, add a possible
.1% of negative error, will go to 1.248V, so it is already 2mV, drop
your accuracy to below 9 bits... pretty scary, huh?

We are not talking about a cheap 91 cents Vref, but about the 30ppm (one
of the best at the market) LM4040, with the best possible available at
Digikey with 0.1% of error, the most expensive one, around $5 per unit,
and that thing can't really goes up to 12 bits at 0¡C???? Yes!

What happens here is that you need to deal with all the possibilities.
First, you need to compensate and should trust in calibration. If the
unit is actually with 0.1% of error, the calibration will fix it, IF the
unit keep the error permanently.  Second, temperature offset and
deviations should also compensated by software, for that you need to use
a temperature sensor and calibrate the unit for different temperature
ranges, so the software would know where to look and how to do.

Going to your problem.
----------------------
2mV noise is pretty high.  How do you get it? How do you measure it?  at
the ADC output? or with an oscilloscope?. What is your signal source?
what impedance it offers?  To work with very low signals, it is *VERY*
important to match impedances, if not, bounced signals can kill the
original and clean one.  Sometimes a capacitor creates more problems
than solve. A capacitor is not a God's creation. It leaks, it farts, it
dirts all over the place in very low voltage.  
At 24 bits, nanoVolts range, a single electron leaking at the cap plates
can creates a bouncing signal at the ADC input.  
Here again, expensive and good polypropylene caps makes a hell of a
difference from cheap ones.

What happens if you short circuit the ADC input, still having the noise?

The trade-in here is to avoid at any cost high gain amplifiers, try to
deal with the signal as pure as it is, avoid intermediate circuits,
resistors, dividers, filters, whatsoever that can transform your life in
a live hell.  Signal treatment is a long and extensive learning at any
electronic university, and it is not any teacher of this subject that
can build a nice front-end amplifier to work with a 24 bits A/D.

Answering your subject question; Yes, at 24 bits A/D, we really ARE at
the twilight zone, doomed, alone, in total fear, no support, no
experience around, no books, no fancy "do it by yourself multicolored
animated gif playing at your screen"... just plain despair!

Keep contact.
Wagner.

PS: Just try and turn off the PC and that fluorescent lamp over your
bench, and see if the 2mV disappear... :)  


Dan Michaels wrote:
{Quote hidden}

2000\04\24@202143 by David VanHorn

flavicon
face
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1


>Am I at the tradeoff point in my design? Is there some magical
>Noise-vs-??something??  formula here I forgot about [like trading
>gain for bandwidth]? Also, they are putting 16-bit sound cards
>into PCs nowadays. What the heck do those guys know, that they
>can accomplish that?

Begin at the beginning :)

Decouple your supplies into the op-amp.  A series R and local C to ground
should work well.

Check the op-amp PSRR AT the frequency of your main interference.

Use a spectrum analyzer to check everything, not just a scope.

Using a SMPS?, trigger the scope with the SMPS, and then go hunting noise
with the other input.

Make sure your local ground is quiet, and does not have someone else's
return current running through it. On my check reader board, I had two
700mA chopped stepper drivers less than an inch away, and got zero pickup
from that. Or the uP, or the SMPS. Un-measurable.

In the circuit itself, lower the impedances if you can, keep layout tight,
don't ground or decouple to any foreign points.

- --
Are you an ISP?  Tired of spam?
http://www.spamwhack.com  A pre-emptive strike against spam!

Where's Dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9

-----BEGIN PGP SIGNATURE-----
Version: PGPfreeware 6.5.2 for non-commercial use <http://www.pgp.com>

iQA/AwUBOQT++IFlGDz1l6VWEQIpYQCeLq58NHtbpb1ZJRA5wQ9ltNdR3AsAn1Pq
LkMoQ/GbkYuY6XVm610qkEyx
=Tu/C
-----END PGP SIGNATURE-----

2000\04\24@203607 by David VanHorn

flavicon
face
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

U want fun?

My current bugaboo:

I have a board that has to deliver a 30mV (full scale) signal to another
board.
That board emits 6 watt RF pulses at 916 MHz on an antenna 0.25" from my
board, and it takes 2A current pulses 50uS wide, with nice sharp edges.

The return current was the major problem, since the mic is a single ended
input. Transformer coupling solved that one, now I'm dealing with direct
rectification effects. I go tomorrow up to ames labs to evaluate the new
PCB.  We'll see what happens!


- --
Are you an ISP?  Tired of spam?
http://www.spamwhack.com  A pre-emptive strike against spam!

Where's Dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9

-----BEGIN PGP SIGNATURE-----
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iQA/AwUBOQUCC4FlGDz1l6VWEQL47ACfTTNm97sHTd7Ip68HeBIb5ekAlFIAn3kF
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=qEjU
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2000\04\24@214002 by Sean Breheny

face picon face
Hi Wagner,

At 07:48 PM 4/24/00 -0400, you wrote:
>some state it. Some of them have milli-volts of noise (white noise,
>pink, whatever), it is an intrinsic silicon noise, can't be removed,
>can't be filtered, there is NO capacitor can avoid it, stabilize or
>level it.  You just need to check the manufacturer document (specs

I don't see why you couldn't low-pass filter the output of the reference?
Prodiving that the thing that is using the ref isn't drawing much current
from it, you could just put a resistor in line and add a low-leakage cap
after it.

Even if the thing that needs the reference needs to draw a good deal of
current, you could buffer with a low-noise op-amp and still do the LPF.

Sean

|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
TakeThisOuTshb7EraseMEspamspam_OUTcornell.edu ICQ #: 3329174

2000\04\24@215650 by Sean Breheny

face picon face
Hi Dan,

I think you went past the BW consideration too quickly. There is a BIG
difference between getting  uV resolution in a 3HZ BW and in a 1 MHz BW.

I have been working on Cornell's Autonomous Helicopter project and we are
pushing MuRata rate gyros to their limits. They give 640uV per deg/sec. I
measured their output noise using the best low-noise amp I could make and I
got 0.05 deg/sec noise floor in about a 50Hz BW (amp noise + gyro noise)
which corresponds to 32uV of noise.

I then designed a circuit on a double-sided circuit board with the top
almost dedicated to ground plane. I kept the digital and analog GND planes
separate except at the connection point of the main GND wire. I placed the
recommended bypass caps for the AD974 (the 16-bit 200ksamp/sec ADC we are
using) and I bypassed the supplies to the op-amps in the circuit). I got a
final noise of 0.066 deg/sec for the whole system, which corresponds to 42
uV. I obtained this on the first try, by just following the manufacturers
recommendations and using careful layout and limiting BW when I could (I
think this is key). I have an (AVR ;-) ) micro running on the same board,
inches away.

Also, I think I was able to improve the noise performance by amplifying my
signal so that my minimum resolution corresponded to a couple of bits on
the ADC, so I wasn't pushing the ADC to its limits.

Sean

At 02:49 PM 4/24/00 -0600, you wrote:
{Quote hidden}

| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
RemoveMEshb7spamTakeThisOuTcornell.edu ICQ #: 3329174

2000\04\24@225408 by Wagner Lipnharski

flavicon
face
Yes, I thought the same, did several different kind of passive filters.
Used from pico to microFarad capacitors, different capacitors, diferent
resistors. Looks like the microVolts noise increase with some
capacitors... leaking?  Used a filter like this, no change at all.

      1k       1k                   1k       470
+5V----R---o----R-----o-----o----o---R---o-----R----o-----o--->
          |          |     |    |       |          |     |
         ===        ===   ---  ---     ---/       ===   ---
         ---        ---   ---  ---      A   1.2V  ---   ---
          |          |     |    |       |          |     |
         Gnd        Gnd   Gnd  Gnd     Gnd        Gnd   Gnd

       100uF      220uF  0.1uF  82pF            330uF  0.1uF

When you read the documentation you will understand why they offer it in
different noise levels, still the same unit, cost 3 or 4 times more.
The noise can reach low frequency, in some rare situations I noticed it
as low as 0.5Hz.  National website pdf file about the LM385
http://www.national.com/ds/LM/LM185-1.2.pdf state at page #4, two graphs
about noise, the second show a single pole low pass filter where the
noise is reduced from 60uV to 55uV at 100kHz noise, with a sharp cutoff
filter it is reduced to around 35uV... so no game, noise still there.
The low voltage noise is difficult to remove.

Wagner

Sean Breheny wrote:
{Quote hidden}

2000\04\25@121404 by Dan Michaels

flavicon
face
Joe, Grif, Wagner, Dave, thank you all for the responses.
I think I have been around the track a couple of times with
pretty much everything you all mentioned.

Bypass caps everywhere, as much physical separation between
analog and digital sections as possible given a 3"x5" pcb,
"separate gnd busses" for analog and digital, analog gnd
single point connection returned directly to power entry point,
as much gnd planing as possible on a 2 layer pcb, wide power
traces, separate analog regulators, lowest feasible R values
on opamp ckts, 2 opamp inverting stages in series, not using
non-inverting stages, ferrite bead in power in lead and Rs-232
line.

Also, pcb is in an EMI-shielded ABS case, and with case
removed, the noise *is* always 2x to 3x to 5x higher. [I
wonder if this isn't "the" crucial clue?]. I assume this
means pickup from local digital sections of pcb is what is
being shielded. I don't think it's coming from outside.
=================

Some specifics:
- 2 mV noise is referenced to input, with input grounded
 directly and measured by reading A/D output, not with scope.
- for this measurement, input range = +/-1.25v, so 2 mV
 represents only about 9 bits - so am losing ~3 A/D LSBs.
- Power train:
 - wall wart -> 7812 --> 7805 (digital).
                 "   --> 78L06 (analog +).
                 "   --> 7662 (-12v) --> 79L06 (analog -).
 - all regs bypassed, filtered high side, low side, etc.
- Gnd planes present under noisy 7662 (766x derivative). Noise
 referred to above is broadband noise, not correlated to 7662
 switching.
- Analog circuitry: 2 inverting op amp stages (superior CMR to
 non-inverting), currently using TLE2072, 4 gains set via '4052.
 - Lowest range: +/-1.25v, Av1=0.4, Av2=4.
 - R values: 1st stage - 1M in, T-section feedback to lower
   effective R, with 82K-21K-68K. 2nd stage 12K in, 50K fb.
 - both stages switch gain via '4052 mentioned above.
 - output to A/D thru small R.
 - opamp/CMOS switch bypassed directly at pins.
- A/D: LTC1400, SOIC, 12-bit, 8-pin, internal Vref, SPI control
 at 6.4 Mhz. Vref bypassed directly at chip. Vdd, Vss bypassed
 close to chip.
- Digital control: PIC76 @ 20 Mhz, bypass caps in several places,
 gnd planes under chip, gnd island around xtal.
 - no hi-speed signals passing near analog circuitry.
 - 2 DC control signals from PIC to '4052, bypassed.
- RS-232 connection to pcb: lots of noise was originally measured
 on the TX line from the PC, and now has a ferrite bead inline.

Note - overall, this is a "system-level" problem. Mixed
 analog-digital, small space, noisy 7662, R values as small as
 I can make them, RS-232 to PC, wall wart power, etc. I have
 isolated and dealt with any number of noise sources already.

Working on next pcb layout:
- moving analog regs further away from PIC.
- removing 7812 from inline with 7805.
- considering moving single-point analog gnd connection from
 78L06/79L06<->power_entry_point to under A/D.

Note - I have several times fiddled with the opamp ckt design
 and R values, and they are about as low as I can go now, and
 still keep Rin = 1M.

I may need to go to a completely different front-end design, ie
FET follower amp - unfortunately this is much more complicated,
requires lots more space, it drifts, etc/etc. I was hoping to
keep the front-end design simple and straightforward, since
BW is only 1 Mhz, but I am beginning to wonder.
=============
=============

Re what Dave said:
>Decouple your supplies into the op-amp.  A series R and local C
to ground
>should work well.

Bypass caps are "everywhere", but I haven't tried series R in
the opamp power leads. However, they have their own regulators,
bypassed and separate from the digital regs, plus a separate
analog gnd, too. So I don't think a series R here will help much.
=================

>Check the op-amp PSRR AT the frequency of your main interference.
>
>Use a spectrum analyzer to check everything, not just a scope.

Measured noise is pretty wideband, not correlated to PIC xtal
or 7662 - [xtal is outside passband, 7662 has been dealt with].
===============

>In the circuit itself, lower the impedances if you can, keep
layout tight,
>don't ground or decouple to any foreign points.

I already have lowered the R values in the analog section as
far as I think I can go. The 2 mV noise was measured with input
BNC shorted.

"... gnd or decouple to a foreign point". What does "foreign"
point" mean?
====================
====================

Re what Joe mentioned:
>And yes, you may be missing something.  You can trade off bandwidth for
>noise! The narrower the bandwidth, the lower the noise figure. Every time
>you reduce bandwidth to 50% noise is decreased  to 35%.  Its one of those
>square law formulas I learned in Signals.

I am pretty familiar with signal theory, but this is a wideband ckt,
and the analog has to be made to tow the line. BW here is 1 Mhz, and
I wish I could make it 20 Mhz!!  [I could probably get Walter's 0.12
uV, if I LP filtered down to 3 hz. Yeah, right].

------->  My wondering was whether there isn't some magical formula
saying something like "for a 1 Mhz BW, no matter how damn hard you
try, you aren't ever gonna get the noise below ___ mV, unless you
do ........". [as in, "make the Rs all <= 1K", whatever].
===============

>There are other exotic methods for squeezing the last little bit out of a
>signal path, synchronous detectors, digital filtering, extremely long (over)
>sampling, etc.

My case is 1-shot waveform captures, and I want to make the ckt
work as well as possible *before* the DSP stuff comes in [which it
does later on].
===============
===============

RE what Wagner mentioned, I am still mulling over your comments.
Lots of good info there. The Vref on my LTC1400 A/D is inside
the chip, bypass caps outside. Noise measured via A/D binary
output, with front-end amp tied hard to gnd.

>Here again, expensive and good polypropylene caps makes a hell of a
>difference from cheap ones.

My only caps are ceramic bypass and electrolytic P/S filtering.
Where did you use polypropylene? For coupling?
==============

Whew, what a marathon. Given all this, if there is something
I have clearly overlooked, ....... ????????

Best regards,
- Dan Michaels

2000\04\25@121408 by Dan Michaels

flavicon
face
Appendix to marathon note:
........
>>Here again, expensive and good polypropylene caps makes a hell of a
>>difference from cheap ones.
>
>My only caps are ceramic bypass and electrolytic P/S filtering.
>Where did you use polypropylene? For coupling?
==============

Oops, forgot about the small caps [1-20 pF range] across the op
amp feedback Rs, used for overshoot & BW control. Ceramic.
Would polypro work better here?

regards,
- Dan Michaels
==============

2000\04\25@121434 by Tom Handley

picon face
  Dan, I'm currently working on a PIC-based DAQ system that uses the
LTC2400. Others have mentioned noise problems and techniques with
low-voltage measurement. I think the key here is that the LTC2400 family are
extremely accurate converters that can provide very accurate measurements at
lower resolutions. I'm using 16-18 Bits for display while averaging all the
Bits. The software provides for calibration.

  Wagner mentioned reference noise which is a good point that is sometimes
overlooked. I'm using a MAX6341 4.096V reference with a 1ppm/C Tempco, 0.02%
initial accuracy, and around 2.5uV of noise. It provides a pin for an
external cap which augments wide-band noise reduction. With 24 Bits the
resolution is ~244nV. As is pointed out in one of Analog Devices'
applications books; 600nV is the Johnson Noise in a 10KHz BW of a 2.2K
Resistor @ 25C. So, yes, this really is the "Twilight Zone" ;-)

  The LTC2400 is extremely easy to talk to but you must decide which mode
to use. In my case, I use the External SCK/Single Cycle/Reduced Data mode.
With /CS initially High and SCK initially Low, the basic flow is:

     Wait for End of Conversion:
     - Set /CS Low
     - Wait for SDI Low

     Shift-in first 4 Bits (EOC -> Dummy -> Sign -> Extended Range)

  At this point, you have Bits 31..28 in Data register Bits 3..0 where:

     Bit 31 (3) = End of Conversion Bit
     Bit 30 (2) = Dummy Bit
     Bit 29 (1) = Sign Bit
     Bit 28 (0) = Extended Range Bit

  The next Bit is the MSB of the conversion where Bits 27..4 are the 24-Bit
result and Bits 3..0 are sub LSB's that can be ignored or used in averaging.

  - Tom

At 02:49 PM 4/24/00 -0600, Dan Michaels wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

2000\04\25@122723 by Don Hyde

flavicon
face
Well, I did software on a project where my code turned the switcher off long
enough to make the actual measurement -- took a lot of C, and a linear
regulator to clean up the droop, but it worked.  We needed the switcher to
get 2.4V or whatever from an end-of-life 3v cell up to 5v, but the op-amps
and digitals could go on 4.5 or so.

> {Original Message removed}

2000\04\25@133222 by Craig Lee

flavicon
face
You could also put little RCs at the source of digital signals to
attenuate the high frequency components that are more likely to
radiate.  Requires that you know your maximum frequency to select
the RC. (has this been said already?) ie. LSB changes fastest...

Craig

{Original Message removed}

2000\04\25@140314 by Wagner Lipnharski

flavicon
face
Dan Michaels wrote:
[snip]
> My only caps are ceramic bypass and electrolytic P/S filtering.
> Where did you use polypropylene? For coupling?
> ==============

As I said before, working with Volts, even mV, it doesn't care so much
what type of capacitor you use, but goint to microVolts or even
NanoVolts, things change drastically. Very low leakage filter capacitors
are very important.  At 500nV, how many electrons do you think would be
necessary to leak from one capacitor's plate to another to bouce the
voltage to 510nV? not a bunch.  How many bits into the A/D it means? a
24 bits ADC would suffer with that change at the vref. Some
Polypropylene Film ECQP(U) (Panasonic) offers a minimum isolation of 45
GigaOhms, probably your circuit board will have less isolation between
tracks.

Just a question: THe 2mV readed at the A/D output is a jumping noise or
a steady noise, that can be confused with a/c or d/c A/D input offset?

Another point is that I never use a 16 bits ADC to read 16 bits
signals... I just ignore last 3 or 4 bits, so I pay more for a steady
conversion... using an expensive 22 bits AD7713 to really read 18
bits... going now to the LTC2408 (24 bits that in real are 28 bits) to
use just 20 bits... that's the deal, come on, it is a 6 digits counter
with 20 bits!!! I can have a resolution of 10nV at 10mV range...
(9.999,99)

> The Vref on my LTC1400 A/D is inside the chip,
> bypass caps outside. Noise measured via A/D binary
> output, with front-end amp tied hard to gnd.

What about short to ground the LTC1400 inputs? not just the front end
amp inputs...  You need to isolate and make sure where is the origin of
the noise.

Wagner.

2000\04\25@140728 by Wagner Lipnharski

flavicon
face
Even a good polypropylene or polyester cap can generate noise if you are
out of luck.
A good way to check those guys is increase the op-amp gain to the max
rail limits and check the noise generation, so you could play with
components until you find out the ones that would benefit you with low
noise, then reduce op-amp gain to the correct gain.

I already made few op-amps high impedance gain, that the input coupling
cap + resistor could not touch the circuit board... yup, just in the
air, the best isolator I know.

Wagner.

Dan Michaels wrote:
{Quote hidden}

2000\04\25@141554 by Wagner Lipnharski

flavicon
face
Tom Handley wrote:
>
>    Dan, I'm currently working on a PIC-based DAQ system that uses the
> LTC2400. Others have mentioned noise problems and techniques with
> low-voltage measurement. I think the key here is that the LTC2400 family are
> extremely accurate converters that can provide very accurate measurements at
> lower resolutions. I'm using 16-18 Bits for display while averaging all the
> Bits. The software provides for calibration.
>
>    Wagner mentioned reference noise which is a good point that is sometimes
> overlooked. I'm using a MAX6341 4.096V reference with a 1ppm/C Tempco, 0.02%
> initial accuracy, and around 2.5uV of noise. It provides a pin for an
> external cap which augments wide-band noise reduction. With 24 Bits the
> resolution is ~244nV. As is pointed out in one of Analog Devices'
> applications books; 600nV is the Johnson Noise in a 10KHz BW of a 2.2K
> Resistor @ 25C. So, yes, this really is the "Twilight Zone" ;-)

Yes, I forgot to say, using a high voltage Vref, like 4.096, the silicon
noise is the same from the smaller ones, so the relation Vref/noise is
increased.  I did it once, even using 0.1% 10ppm matched pair resistors
(If I remember well) to reduce the Vref it worths, the final noise is
also reduced.

The Max62xx/63xx units are very steady ones, of course they need to
justify the cost above $10 :)

2000\04\25@150803 by andy howard

flavicon
face
From: "Dan Michaels" <EraseMEoricomspamLYNX.SNI.NET>

> Joe, Grif, Wagner, Dave, thank you all for the responses.
> I think I have been around the track a couple of times with
> pretty much everything you all mentioned.
> Bypass caps everywhere, as much physical separation between
> analog and digital sections as possible given a 3"x5" pcb,
> "separate gnd busses" for analog and digital, analog gnd
> single point connection returned directly to power entry point,
> as much gnd planing as possible on a 2 layer pcb, wide power
> traces, separate analog regulators, lowest feasible R values
> on opamp ckts, 2 opamp inverting stages in series, not using
> non-inverting stages, ferrite bead in power in lead and Rs-232
> line.
> Also, pcb is in an EMI-shielded ABS case, and with case
> removed, the noise *is* always 2x to 3x to 5x higher. [I
> wonder if this isn't "the" crucial clue?]. I assume this
> means pickup from local digital sections of pcb is what is
> being shielded. I don't think it's coming from outside.



Hi Dan.

I don't know if you've seen
http://www.channel1.com/users/analog/noise.html.  It's a useful
discussion of noise reduction, mostly focussed on PCB layout issues.

In fact the whole site is very interesting with loads of useful hints
and tutorials about analogue electronics with a very practical bias.
Well worth a look IMO.


Cheers

Andy.

2000\04\25@162657 by Dan Michaels

flavicon
face
Thanks to Sean, Don, Craig who also responded here. Some
additional thoughts regarding my noise problem:

Grif wrote:
.........
Have you tried moving the first op amp into a separated, shielded box, with
.....
 Feed thru's on the
power into the box,,, and signal in and out of the box. and a separate
regulator, make sure you don't let any left over noise on the input side to
the regulator couple to the ground or output of the regulator.
.........

Thanks, for the many suggestions. I think I have already incorporated
most of them. However, thermal control - not on this thing!! Also, the
front-end amp isn't separately shielded, but is as far from the digital
cktry as possible, has gnd planing under all the chips/Rs/etc, has the
EMI-shielded ABS box overhead, consists of 2 inverting amps in series,
has separate V regs and busses, low-Z 2nd amp, etc.

The one thing I might try on the new layout is returning the bypass
caps on the analog V-reg hi-sides straight back to the power entry
point. They return to the analog gnd buss now. Might help.
=====================
=====================

Wagner wrote:
.........
>The biggest problem I found years ago with low voltage is really noise
>in voltage reference generators.
.........
>the twilight zone, doomed, alone, in total fear, no support, no
>experience around, no books, no fancy "do it by yourself multicolored
>animated gif playing at your screen"... just plain despair!
..............
>PS: Just try and turn off the PC and that fluorescent lamp over your
>bench, and see if the 2mV disappear... :)
>

This was good info you provided on your experiences with V-references.
[And I'm gonna ignore all that "total fear" & "plain despair" talk.
Sun's out today. I need to get < 1 mv noise, before worrying about
10 uV. :-)].

Considering I am using the LTC1400 with builtin Vref, there isn't much
I can do in this arena, except external bypassing, heavy traces, etc,
which I do now. I would think the 1400's Vref would be commensurate
with 12-bit ops.

Is it your experience, Wagner, that onboard Vref is worse than
external? After all, the A/D's 6.4 Mhz internal SPI cktry is only
microns away.

I did discover the PC sends piles of hash out the RS-232 line, and
of course, the monitor is a great broadcaster. I did some controls for
this, added a ferrite and shielded cable to the RS-232 line, and started
using EMI-shielded ABS cases [huge improvement, as noted before].

I probably should go thru another round of testing, to try to localize
the noise source(s) better. It is pretty broadband, but thinking about
it, I should do more scope/triggered/source_correlation measurements,
since end-to-end measurements suffer from aliasing in the A/D.
================
================

Anyone have any ideas regards the great noise reduction I see
when the EMI case is put on?

I do think this is shielding LOCALLY-generated noise, rather than
external. I presume "radiated" E-noise, because conducted and
H-noise would not be affected as much by the shield. Correct?

I do know that the shielding greatly cuts radiated E-noise from
the 7662 and local VCO chip [those sources were already dealt
with, BTW, via gnd planing and separating gnds, and easy to
measure since can be correlatd]. I do not believe I have any
serious inductive loops in the "digital" section - the power
and gnd busses and signals all run pretty much in close
parallel formation there.

Please don't anyone suggest "multi-layer" pcb for this project.
I'll have to accept 2 mV noise over that option.

Cheers,
- Dan Michaels
Oricom Technologies
===================

2000\04\26@002623 by Dan Michaels

flavicon
face
Craig Lee wrote:
>You could also put little RCs at the source of digital signals to
>attenuate the high frequency components that are more likely to
>radiate.  Requires that you know your maximum frequency to select
>the RC. (has this been said already?) ie. LSB changes fastest...

Yeah, good point. Thanks. I was actually thinking about this
after I mentioned yesterday that I have 2 DC control signals
going from the PIC over to the '4052 that select the 4 gains
in the analog section. The lines are bypassed at the '4052,
but a series R would probably help too, to bandlimit possible
hash. [what the heck - adds only a few more components to the
200 already on the board].
================
================

Sean Breheny wrote:
....
>I think you went past the BW consideration too quickly. There is a BIG
>difference between getting  uV resolution in a 3HZ BW and in a 1 MHz BW.
....
>got 0.05 deg/sec noise floor in about a 50Hz BW (amp noise + gyro noise)
>which corresponds to 32uV of noise.
....
>final noise of 0.066 deg/sec for the whole system, which corresponds to 42
>uV. I obtained this on the first try, by just following the manufacturers
>recommendations and using careful layout and limiting BW when I could (I
>think this is key). I have an (AVR ;-) ) micro running on the same board,
>inches away.
....

16-bit, 42 uV, AVR inches away. "first try". Shoot, that's just
too easy!! How can you learn anything when it's so easy? :-).

Yeah, I realize BW = 50 hz vs 1 Mhz is a major factor. Noise voltage
is related as what, sqrt[BW1/BW2]. Yes ?????

So, 2mV * sqrt[50/1,000,000] = 2mV * 0.007 = 14 uV. Sounds good, but
something is still off. My 100 Mhz Hitachi scope has < 1 mV of
noise with the input dead shorted.
===============
===============

Tom Handley wrote:
..........
>   Wagner mentioned reference noise which is a good point that is sometimes
>overlooked. I'm using a MAX6341 4.096V reference with a 1ppm/C Tempco, 0.02%
>initial accuracy, and around 2.5uV of noise. It provides a pin for an
>external cap which augments wide-band noise reduction. With 24 Bits the
>resolution is ~244nV. As is pointed out in one of Analog Devices'
>applications books; 600nV is the Johnson Noise in a 10KHz BW of a 2.2K
>Resistor @ 25C. So, yes, this really is the "Twilight Zone" ;-)
>

The largest resistor in my analog ckt is the 1M input on the 1st
stage, so Johnson noise for it at 1 Mhz = 0.12 mV. Well below my
2 mV measured noise. So, that's not a problem here.

Tom, from your experience, do you think the internal Vref ckts
found in [some of] the A/D converters are as noise-free/stable/etc
as the external Vref ckts you've been using???
==================
==================

Well, all in all, it's sure good to find out I'm the only guy
around here who can't get his stuff to work down into the uV
region. !!!! Hmmm, guess it's just a matter of finding that magic
configuration, afterwards which all is golden. Back to the lab.

Cheers and thanks for all the input,
- Dan Michaels
Oricom Technologies
===================

2000\04\26@010738 by Plunkett, Dennis

flavicon
face
26/4/2000


No this is not the twilite zone at all, infact relality!
You cna keep the 24bit resoultion and still be OK.
Note that we are talking of while noise whos bandwidth is infinite in both
directions and the effective sum of the power is (Zero) think before you
respond.
Ok so what can we do about its, as often we will have this noise flip and
change the state of a signal, very much unwanted!
OK remember that the effective power is Z-E-R-O? but at any one time it may
be at the maximum or at the minimum correct also? So what would happen if
your where to mix in another while noise source of equal maximum and minimum
amplitude swings over a period of time? Would there not be a high chance
that the resultant mixing of these two white noise signals be also or near
zero for most of the time?
Now here is the tricky question, over the same infinte period is the
resultant signal power also zero?
You will find that this is often called bit jittering!


Dennis





> {Original Message removed}

2000\04\26@042044 by Russell McMahon

picon face
Dan,


1.    It's vital that your op-amps have good gain at the common mode
frequency.
ie - even if you are amplifying a dc or low frequency signal, if you have
digital (eg clock, uP data, SPI signals etc) appearing as common mode
signals then your op-amps MUST be able to reject these actively . ie you
should be using amps with a 10MHz plus gain bandwidth and really the more
the better! A low gbw opamp will pass the common mode signals as noise in an
uncontrolled way.

2.    Consider using parts like the AD7730 or the newer AD7731 with internal
gain switching. I haven't used these personally but they are very well
spoken of by friends of mine with much experience in this area.

3.    If I was doing this (and I'm glad I'm not just at present :-)) I would
consider building a minimum component configuration just to see how good I
could make it with the IC used.
eg

- No gain switching 4052
- No potentially noisy adjacent 766x adjacent.
- Power rails sourced from some rather external stable source with copious
local filtering.
- SPI control chip farish away with decoupled well shielded control lines.
- House in ferrous box.(need not be pretty or fancy.*
- etc

ie get rid of everything possible

Once you are sure of how well you can make the simplest possible circuit
perform you can then extend it and see where it starts to degrade.


* For "proof of principle" in suspect environments I have used light "steel"
element covers intended to make range tops look prettier when elements are
not in use. These make a nice flat steel sheet with a turned up edge and 2
can be nested (bottom one upside down) to make an easy open enclosure. Cut
holes, use feed throughs etc as required You do have a complete annular open
ring when these are nested but it is vanishingly small - especially if you
put a weight on top. Aint pretty but it helped me.

     *********************
*    *                              *    *
*    *                              *    *
*    *                              *    *
*****************************





     Russell McMahon
_____________________________

>From other worlds - http://www.easttimor.com
                               http://www.sudan.com

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))


{Original Message removed}

2000\04\26@124824 by Dan Michaels

flavicon
face
Dave Van Horn wrote:
.....
>Check the op-amp PSRR AT the frequency of your main interference.
.....

Dave, it hadn't escaped my attention that you mentioned this the
other day. This may be much of the problem. I am currently using
the TLE072 dual op amp, with gain-BW product = 10 Mhz. It's about
the best thing I could find that looked comparable to the ckt reqs.
I upgraded from the slower LF353 when I started pushing the BW up.

I just re-checked the specs. The CMRR of the TLE072 drops to 50
dB at 1 Mhz, the PSRR+ to 50 dB, and the PSRR- to only 20 dB.

Note, I earlier canned the LF353 because its PSRR- drops way down
to 2 dB at 1 Mhz! Also, I originally went with the inverting
opamp config because of the CMRR dropoff.

This may be the real problem with my board. So what is the
solution?

1. Anyone know of a good dropin DIP-8, dual op amp replacement
  with better PSRR?

2. Would it help to work on the analog -V regulator [79L06] a
  little harder? I already have bypass and filter caps there,
  and on the opamp, plus 50 mil power traces. OTOH, it does
  get its power from the noisy ole 7662, and on the present
  pcb, its fairly close to the PIC. [on the new pcb I had
  already moved it away].

3. Maybe something other than 79L06 would be better.

best regards,
- Dan Michaels
Oricom Technologies
===================

2000\04\26@141013 by Grif\ w. keith griffith

flavicon
face
<x-flowed>I guess the next step is start breadboarding the thing one part at a
time.  Do the front end,,, no digital stuff at all, battery powered,
running clean.  Then start adding stuff.

Big snips,,,


>Grif wrote:
>.........
>Have you tried moving


'Grif'   N7IVS

</x-flowed>

2000\04\26@142424 by Dan Michaels

flavicon
face
Dennis wrote:
>No this is not the twilite zone at all, infact relality!
>You cna keep the 24bit resoultion and still be OK.
>Note that we are talking of while noise whos bandwidth is infinite in both
>directions and the effective sum of the power is (Zero) think before you
>respond.
>Ok so what can we do about its, as often we will have this noise flip and
>change the state of a signal, very much unwanted!
>OK remember that the effective power is Z-E-R-O? but at any one time it may
>be at the maximum or at the minimum correct also? So what would happen if
>your where to mix in another while noise source of equal maximum and minimum
>amplitude swings over a period of time? Would there not be a high chance
>that the resultant mixing of these two white noise signals be also or near
>zero for most of the time?
>Now here is the tricky question, over the same infinte period is the
>resultant signal power also zero?
>You will find that this is often called bit jittering!
>

I think I have the general idea of what you are talking about here.

>From information theory, encryption works because you can take a
non-random bit stream and XOR it with a random stream, and the result
comes out random. Likewise, I have read that you can add a small
amount of random noise to an image that has non-random hash on it,
like streaking, banding, washedout areas, pixellation, etc, and
greatly improve the overall image quality.

So it stands to figure that you can possibly add some random noise
to a waveform that has some non-random interference on it, and
effectively "mask" that interference. I have actually thought
about trying this in the past. Might actually work for small
"nibby" noise, and leave the longer-term waveforms being captured
more or less intact.

Cheers and thanks for the input,
- Dan Michaels
Oricom Technologies
===================

2000\04\26@144723 by Andrew Kunz

flavicon
face
This works quite well.  We use it to get better resolution on communication
signal levels over RF.

Andy










Dan Michaels <RemoveMEoricomEraseMEspamEraseMELYNX.SNI.NET> on 04/26/2000 02:21:47 PM

Please respond to pic microcontroller discussion list <RemoveMEPICLISTspam_OUTspamKILLspamMITVMA.MIT.EDU>








To:      RemoveMEPICLISTTakeThisOuTspamspamMITVMA.MIT.EDU

cc:      (bcc: Andrew Kunz/TDI_NOTES)



Subject: Re: [OT] [EE] 24-bit A/D. Are We in the Twilite
         Zone Here?








Dennis wrote:
{Quote hidden}

I think I have the general idea of what you are talking about here.

>From information theory, encryption works because you can take a
non-random bit stream and XOR it with a random stream, and the result
comes out random. Likewise, I have read that you can add a small
amount of random noise to an image that has non-random hash on it,
like streaking, banding, washedout areas, pixellation, etc, and
greatly improve the overall image quality.

So it stands to figure that you can possibly add some random noise
to a waveform that has some non-random interference on it, and
effectively "mask" that interference. I have actually thought
about trying this in the past. Might actually work for small
"nibby" noise, and leave the longer-term waveforms being captured
more or less intact.

Cheers and thanks for the input,
- Dan Michaels
Oricom Technologies
===================

2000\04\27@133631 by Dan Michaels

flavicon
face
Grif wrote:
>I guess the next step is start breadboarding the thing one part at a
>time.  Do the front end,,, no digital stuff at all, battery powered,
>running clean.  Then start adding stuff.

Yeah, I do this with my s.w., when I have something I can't fix any
other way. With h.w., it's so much harder. I have done a lot of
testing in the past, mostly on the finished pcbs, removing other
chips, adding caps here and there, etc.

I think this is more a "systems-level" problem and has to be fixed
in place, so I've been going the route via first principles.

That is, I read everything I can find on low-noise analog and
high-speed digital design, and then incorporate those ideas into
the pcb design, etc, and then test and work with that. I think
sometimes the sum is greater than the parts [gee, sounds like
something *you* would say - yes?].
==============

Wagner wrote:
>
>Just a question: THe 2mV readed at the A/D output is a jumping noise or
>a steady noise, that can be confused with a/c or d/c A/D input offset?
>
>Another point is that I never use a 16 bits ADC to read 16 bits
>signals... I just ignore last 3 or 4 bits, so I pay more for a steady
..........

Not an offset issue, I think, rather fuzz that overwhelms the lowest
2 LSBs. And for a 12-bit A/D I was hoping to get better than 9.5 bits.
============

>> The Vref on my LTC1400 A/D is inside the chip,
>> bypass caps outside. Noise measured via A/D binary
>> output, with front-end amp tied hard to gnd.
>
>What about short to ground the LTC1400 inputs? not just the front end
>amp inputs...  You need to isolate and make sure where is the origin of
>the noise.
>

Yeah, I need to go back and do some more testing. Try to isolate
and correlate noise with possible sources - exactly. All the older
pcbs are gone now, and I am finishing a new layout, and so will
do more tests once I get those. Also, see above answer.

Thanks for the suggestions,
- Dan Michaels
================

2000\04\27@133827 by Dan Michaels

flavicon
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Andy Howard wrote:
.....
>I don't know if you've seen
>http://www.channel1.com/users/analog/noise.html.  It's a useful
>discussion of noise reduction, mostly focussed on PCB layout issues.
....

Thanks for the link. I looked at it, and it's a very good overview
of the issues. I think I've dealt with most of them, based upon
other readings. Other useful links in this area are:

www.national.com/apnotes/apnotes_all_1.html
AN643 - EMI/RFI Board Design

www.fairchildsemi.com/apnotes/ap_notes_all.html
AN-389: Follow PCB Design Guidelines For Lowest CMOS EMI Radiation

2000\04\27@133829 by Dan Michaels

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Andy wrote:
>This works quite well.  We use it to get better resolution on communication
>signal levels over RF.
>

Good, do you add the noise in before or after the A/D [if there
is one]?

Not wanting to spend the next 6 weeks looking at theory, I was
conjecturing - let's say you have some high-frequency non-random
interference getting into your system, and being aliased into
the A/D. Even though aliased, it will still have its same spectrum
folded around a few times, but still "coherent" [???????].

So, if you add the "masking" noise to the A/D output [ie, via s.w.
postprocessing] rather than prior to the A/D input, it should
work as well. Yes/no/maybe????

Best regards,
- Dan Michaels
Oricom Technologies
===================

>From ORIGINAL:
>So it stands to figure that you can possibly add some random noise
>to a waveform that has some non-random interference on it, and
>effectively "mask" that interference. I have actually thought
>about trying this in the past. Might actually work for small
>"nibby" noise, and leave the longer-term waveforms being captured
>more or less intact.
>

2000\04\27@150308 by Dan Michaels

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Russell McMahon wrote:

>1.    It's vital that your op-amps have good gain at the common mode
>frequency.
>ie - even if you are amplifying a dc or low frequency signal, if you have
>digital (eg clock, uP data, SPI signals etc) appearing as common mode
>signals then your op-amps MUST be able to reject these actively . ie you
>should be using amps with a 10MHz plus gain bandwidth and really the more
>the better! A low gbw opamp will pass the common mode signals as noise in an
>uncontrolled way.
>
>2.    Consider using parts like the AD7730 or the newer AD7731 with internal
.....
>

My present opamp, TLE072, has 10 Mhz GBW but only 20 dB PSRR at 1 Mhz,
and I've been looking for a better drop-in replacement. Natl has the
LM61x2 series, going to 75 Mhz GBW, but amazingly, the PSRR on every
one of these goes into the mud (ie, <= 20 dB) right near 1 Mhz <-- this
seems to be a magical number.

I checked the AD7730, $28/ea from Arrow. Ugh.

I'm beginning to think you just can't do it all with a simple opamp
ckt lie I am using. To do better than 2 Mv noise, would need to go
with FET follower front-end feeding onto expensive low-impedance,
differential-mode opamp ckts, like they do it inside the scopes.
================

>3.    If I was doing this (and I'm glad I'm not just at present :-)) I would
>consider building a minimum component configuration just to see how good I
>could make it with the IC used.
....
>ie get rid of everything possible
>
>Once you are sure of how well you can make the simplest possible circuit
>perform you can then extend it and see where it starts to degrade.
>

Yeah, Grif and Wagner suggested this too. I'm going to try building
up one of my new pcbs [when I get one] one circuit at a time, and
test, test. This way it will more or less be "in system", maybe I
can pinpoint the key problem aspect this way.

Thanks and best regards,
- Dan Michaels

2000\04\27@162020 by Scott Dattalo

face
flavicon
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On Thu, 27 Apr 2000, Dan Michaels wrote:

{Quote hidden}

PSRR - is the Power Supply Rejection Ratio. Right? If you have NO noise on your
power supply then you can live with such a small value. But it's one of those
theory vs. practice things. So the question I have is, can you reduce the noise
on your power supply and (this is equally important) reduce the power supply
source impedance? The former is probably obvious, however the latter is
important because the output stage of your opamp will cause current to flow
through the power supply. If the power supply has a high impedance, this current
will be converted to a voltage and cause the supply to ripple synchronously to
the opamp's output. If there's a lot of gain in the circuit, then you'll get an
oscillator! (Don't ask how I know :).

It's fairly straight forward to calculate the noise voltage that would be
induced on your power supply leads due to the opamp switching. The 'filter
capacitance' along with equivalent series resistance (esr) can be used to
approximate the filter's impedance. If you look at the max current swing in your
output and say that it's a sinusoidal current source driving (or sinking) the
filter then the voltage swing will be approximately:

 V ~ I * sqrt(R^2 + (1/(2*pi*C))^2)

Which says you want zero R and infinite C...

--------

But, even if you did this filtering perfectly, you need to also look at the
other side of the filter. Ground is not always ground. If the ground to which
this filter is referenced is bouncing around like a trampoline, then it will
couple right into the opamp's supplies. Bummer.

Scott

2000\04\28@051905 by Russell McMahon

picon face
Dan,

I've attached some hopefully helpful comments from my colleagues.  who are
expert in this area. As you will read, they are achieving results that would
be very acceptable to you.


     Russell McMahon
_____________________________

>From other worlds - http://www.easttimor.com
                               http://www.sudan.com

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))


____________________________________________________________


Russell,

Further to our recent discussion re high-resolution ADC's, we have for some
time been manufacturing a universal digitiser based around an AD7730
sigma-delta ADC which achieves much better noise performance than your
PIClist colleage appears be observing.

Our digitiser operates as an addressable node on a four-wire (comms + power)
RS-485 bus running at 0.75Mbit/s and has digital I/O capable of switching up
to 400mA.  A single LM2940 5V analog regulator takes the bus power in and
provides +5V out for digital and analog power and transducer excitation.
The on-board 8051-derived microcontroller runs at 24MHz.  In addition to
accommodating mV-level bridge transducers, an on-board single-ended to
differential converter allows bipolar single-ended inputs up to 10V full
scale.  The unit is constucted on a 2-layer PTH PCB (120x60mm) with a
ground-plane occupying most of the component side of the board.

For reasons I won't go into the ADC is run quite fast with a (pk-pk
noise-defined) resolution of about 15 bits and then additional filtering is
done by the microcontroller which improves this to about 18 bits.  The
filtered 24-bit result is updated internally at about 400Hz but is normally
only read over the bus at about 20Hz.  Input bandwidth is around 10Hz under
small-signal conditions, but large-signal transitions are tracked much more
rapidly using the FASTStep feature of the AD7730 and supporting features in
our own digital filtering.

With a good quality 350-ohm loadcell connected in a typical industrial
environment (most of these are used in the dairy industry) and using the
most sensitive range (10mV full scale) we typically achieve an
input-referred resolution (defined by pk-pk noise) of well under 0.1uV.
Note that this resolution is achieved even in the presence of substantial
mechanical vibration (a primary design requirement). Using a 120kg-rated
loadcell we get better than 1 gram usable resolution in the presence of
floor vibration which generates acceleration forces on the loadcell (when
weighing a 25kg bag of milk powder) equivalent to about 2.5% of the loadcell
capacity (about 3kg pk-pk).

The digitised result is impervious to significant local electrical noise, is
unaffected by the use of a cellphone within 1 metre, and shows no
perturbations when the digital outputs switch inductive loads (pneumatics
solenoids).  The entire system (typically comprising 50 nodes) is powered
from a off-line switching supply.

Interestingly, during development, while we did not have any real problem
with noise limiting usable resolution, we did have difficulty approaching
the claimed drift figures for the AD7730 device.  The problem turned out to
be due to high-frequency noise injection into the ADC front-end being
aliased to very low frequencies which were indistinguishable from offset
drift.

The point I am making is that it can be done (though in our case development
took about 4x longer to get it right that we originally budgeted for).  I
don't know why your colleague might be having problems with noise (I haven't
used the LT sigma-delta converters myself), but has he taken the obvious
step of trying a second device to see if it behaves the same.  ESD damage
will often manifest itself as poor noise perfomance in analog devices.  Also
what happens if he shorts the input of the ADC (directly at the pins) ?  Is
the reference noisy and does the input-referred noise level vary if the
reference voltage is varied ?  Is the noise really analog (could the digital
comms with the ADC instead have a high bit-error rate).  What is he using as
a signal source  - could it be noisy ?

Hope my comments help.

Regards,

Ken Mardle

2000\04\28@232829 by David VanHorn

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Try a different op-amp.

I just got back from a field trip where I discovered that my major noise
source was the op-amp itself rectifying RF. No tracks needed, the chip was
acting as an AM demod, and giving a very nice replication of the
transmitted pulses.

LMC6464 got rid of the problem, rectified pulses now unmeasurably low.
:)

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2000\04\28@233711 by David VanHorn

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>2. Would it help to work on the analog -V regulator [79L06] a
>   little harder? I already have bypass and filter caps there,
>   and on the opamp, plus 50 mil power traces. OTOH, it does
>   get its power from the noisy ole 7662, and on the present
>   pcb, its fairly close to the PIC. [on the new pcb I had
>   already moved it away].

Couldn't hurt, (see my other note on op-amps as AM demodulators!)
It's probably layout driven, can you probe around with a spectrum analyzer
and see what surfaces? It may be that you can get 3-6dB just by re-routing
some tracks.

>3. Maybe something other than 79L06 would be better.

Hmm.. 79L10 followed by 79L06, with intermediate filtering?
Cheap, brute force, probably effective. Got that much headroom?


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2000\04\29@133256 by Dan Michaels

flavicon
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Dave Van Horn wrote:
>
>Try a different op-amp.
>
>I just got back from a field trip where I discovered that my major noise
>source was the op-amp itself rectifying RF. No tracks needed, the chip was
>acting as an AM demod, and giving a very nice replication of the
>transmitted pulses.
>
>LMC6464 got rid of the problem, rectified pulses now unmeasurably low.
.......

Sounds like you could use some front-end RF filtering too. Maybe
ferrite beads in the input signal lines, or inductors in the Vcc
lines, etc.

And I've looked at dozens of op amp specsheets in the past couple
of days. Turns out all of the JFET types have very bad PSRR- at 1
Mhz, only 0 to 20 dB. Even true for Natl LM6152 which is 75 Mhz GBW.

Maxim has nothing usable. Linear Tech has a lot of interesting
new op amps. The LT135x series have enormous slew rates [400-1000
V/us] at nominal GBW [12-70 Mhz], plus nice PSRR [50 dB @ 1 Mhz],
and fairly low Icc ~1-2 mA. Really nice amps.

Unfortunately, these things are very costly [$7, qty 1, Digikey],
and the I[input_bias] is up near 1 uA, so now I need a fancy way
to control DC offset jumps when changing between the 4 amp gains.
What fun!!

Well, in a few days, I'll get an LT1355 and plug it in.

I'm just starting to look at the Burr-Brown amps. No current
catalog here, so have to download datasheets and search thru for
the PSRR, etc, values.

Anybody know a nice opamp with GBW >= 10Mhz, CMRR and PSRR
>= 50 dB at 1 Mhz, low I(input_bias), and under $7? [Ha, see
comment below re Holy Grail].
==================

{Quote hidden}

On my new pcb layout, I've already moved the analog v.regs further
from the digital cktry, improved their hi-side bypassing, and
increased the area of gnd planing around them. I'll see if this
helps when I get in the new pcbs.

And there isn't really too much headroom on the 79L06.
7812 -> 7662 (with -10 -> -11v out under load), and 79L06 requiring
about -9 for regulation. If I go to a 7815 and higher Vin, then
I have even more heat problems dropping Vin down to 5v for the
7805 to digital.

I can't see anything left to do, viz-a-viz layout/etc, short of
going to a totally different P/S design.
============

Ha, this whole thing is beginning to look like the Quest for the
Holy Grail :-). Just call me Percival. I'm trying to improve the
analog system overall ENOB from 9.5 bits, and *at best* will
probably get only 10.5-11 bits. Spend 3 months, countless $$$$,
just to get pittance in improvement. Ahhh, wonderful engineering!!

Best regards, and thanks for the help,
- "Percy"
===================

2000\04\29@140208 by andy howard

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> From: "Dan Michaels" <EraseMEoricomspamspamspamBeGoneLYNX.SNI.NET>

> >>3. Maybe something other than 79L06 would be better.
> >Hmm.. 79L10 followed by 79L06, with intermediate filtering?
> >Cheap, brute force, probably effective. Got that much headroom?

> On my new pcb layout, I've already moved the analog v.regs further
> from the digital cktry, improved their hi-side bypassing, and
> increased the area of gnd planing around them. I'll see if this
> helps when I get in the new pcbs.

Ah, speaking of linear regs, I've often found they can exhibit very high
RF frequency instability. All my designs now have decoupling (10nF and a
few tens of pF) *directly* at the pins of the reg. I found that having
any significant length of track between pins and the decoupling didn't
always clear it up.
















.

2000\04\29@145255 by Dan Michaels

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Andy Howard wrote:
>> From: "Dan Michaels" <RemoveMEoricomKILLspamspamLYNX.SNI.NET>
>
>> >>3. Maybe something other than 79L06 would be better.
>> >Hmm.. 79L10 followed by 79L06, with intermediate filtering?
>> >Cheap, brute force, probably effective. Got that much headroom?
>
>> On my new pcb layout, I've already moved the analog v.regs further
>> from the digital cktry, improved their hi-side bypassing, and
>> increased the area of gnd planing around them. I'll see if this
>> helps when I get in the new pcbs.
>
>Ah, speaking of linear regs, I've often found they can exhibit very high
>RF frequency instability. All my designs now have decoupling (10nF and a
>few tens of pF) *directly* at the pins of the reg. I found that having
>any significant length of track between pins and the decoupling didn't
>always clear it up.

Thanks, this is exactly what is on my new pcb layout. Hopefully, this
coupled with finding an opamp with better PSRR will help. [one can
only hope].

Too bad the turnaround on h.w. is so much more trouble than fixing s.w.
Boy, those s.w. guys got it so much easier than they can possibly know.
[oops, did I say that?].

2000\04\29@192206 by David VanHorn

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>Sounds like you could use some front-end RF filtering too. Maybe
>ferrite beads in the input signal lines, or inductors in the Vcc
>lines, etc.

BTDT. None of that made a noticable difference without changing the op-amp.
I'm going in again now, and re-evaluating all that in case it makes a
difference, but it was too small to observe before.

>And I've looked at dozens of op amp specsheets in the past couple
>of days. Turns out all of the JFET types have very bad PSRR- at 1
>Mhz, only 0 to 20 dB. Even true for Natl LM6152 which is 75 Mhz GBW.

Use the best you can afford, and then fix as much as possible on the layout.
RC filters specifc to the op-amp will help a lot, they will knock 1 MHz
right down.
Those Murata/Panasonic EMI filters are great down there, and cheap too $0.25.


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2000\04\30@084011 by Russell McMahon

picon face
Dan,

Here is the latest response from my friend who has extensive experience
delaing with signals in very real world situations at levels well below what
you are dealing with. I can vouch for his experience and success
commercially. His comment on direct conversion without amplification using a
commercial Sigma Delta chip should be given some consideration.



regards



               Russell McMahon

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++


Russell.

I don't mean to be rude but maybe this guy is flogging a dead horse.

Why doesn't he jut get rid of the op-amp front-end and use a sigma-delta
converter chip with the low-level signal conditioning built in.  At well
under US$15 in moderate quantities the AD7730 is very cost-efective when you
consider that it needs nothing in the way of analog support chips and (with
care) is capable of very high performance.

Analog Devices and Crystal Semiconductor (and probably others) have a whole
range of sigma-delta ADC devices with varying cost/performance tradeoffs,
including several which will give usable input-referred resolutions well
under 0.1uV.  I have used the AD7730, AD7714, and AD7715 and recommend them
highly for sensor applications where resolution is more important than high
speed conversion.

I have also used the AD7750 for power metering  - it is by far the easiest
and cheapest way to build an accurate AC power (or more correctly energy)
metering device.  I believe there is now an improved version (AD7751 ?)
which can better handle variable-frequency inputs (the AD7750 only works of
a narrow frequency range).

I'm not trying to sell AD parts here  - merely to point out that they (along
with other manufacturers) have some very useful devices which though not
cheap, may represent cost-effective solutions both in terms of the
performance they provide and in the substantial reduction in design time
they offer (especially important for low-volume niche products).


On the other subject of engineers doing silly (and often dangerous)
hings  - there seems to be a lot of it about and much of it is absolutely
hilarious.  Maybe there is a commercial opportunity here (modern versions of
Victorian morality tales ?)  - how about acting as a publishing editor for a
book of short stories (promoted via snippets posted on the web).

Sounds as though you could come close to filling it by yourself but I'm sure
there would be plenty of willing contributors.  Like the time I nearly
electrocuted myself under Mums' house while investigating a water leak, or
"the home made arc lamp incidents" (yes two separate ones  - melting the
glass in my bedroom window and burning a hole right through by bedding and
foam mattress to the wire-wove supporting it), or exploding insects on the
back lawn using a 1500uF capacitor bank charged to 2kV and a set of old
multimeter test leads, or the Tesla coil incident (or maybe I should let
Chris Paice tell his own story), or the pirate FM transmitter mounted on a
ramp on top of the U of A chemistry building with a remote release as an aid
to preventing it falling into the hands of the radio inspectors (involving
persons who are now respectively head of an F&P division and a senior
engineer at Talon).

Gavin Higgie could tell the story of the EPROM programmer and the 230VAC
supply (and an engineer at DSE whose name I can't recall could tell a
similar story involving literally hundreds of very expensive (and very dead)
NMOS chips in a top-secret digital signal processing system  - being a
military establishment the poor individual was required to wear the results
of his labours on an arm-band for several days).

You could even cast the net wider and allow non-electrical themes.  That
would admit a large number of "bomb" stories (including of course "RDM and
the Headmaster"), allow Ross to relate his story of the dangers of making
smoke bombs by melting ingredients on a gas stove, not to mention the
dangerous combination of boredom and compressed air (as epitomised while I
was working overtime assembling Eveready torches at Fountain Electronics
when I was 15), the
total destruction of the school chem lab fume cupboard (a small 2H + 0
explosion), and how the front 20 rows at the school drama production were
showered with burning newspaper.

Then there is just plain dumb stuff like having to explain to the NZ Forest
Products Ltd. Accomodation Officer a disassembled (and very oily) motorcycle
engine in the lounge of the company house provided for student vacation
employees, or the dye capsules which mysteriously found their way into the
public swimming pool, or the time I helped roll a spare wheel down one of
Wellington's steeper streets (no real harm done but the consequences could
have been horrendous), or the attempt to shoot a large rat with a spear gun
(stupid at the best of times but doubly so considering we were both in a
small tin dinghy at the time), or the time I broke the fish tank and flooded
the doctors waiting room.

There is also the "penguin" incident  - person on holiday at East Cape
sleeping peacefully in back of small van is woken up in pitch dark by cold
wet flapping fishy-smelly alien monster thing (introduced by so-called
"friends")  - penguin survives ordeal relatively intact but person sustains
deep gash on head which bleeds profusely and by light of feeble torches
makes entire scene look like horror movie.

Now there just has to be a market for book of that kind of stuff.

Regards

       Ken Mardle


'[OT] [EE] 24-bit A/D. Are We in the Twilite Zone H'
2000\05\03@003137 by Dan Michaels
flavicon
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Scott Dattalo wrote:
>
>PSRR - is the Power Supply Rejection Ratio. Right? If you have NO noise on your
>power supply then you can live with such a small value. But it's one of those
>theory vs. practice things. So the question I have is, can you reduce the noise
>on your power supply and (this is equally important) reduce the power supply
>source impedance? The former is probably obvious, however the latter is
>important because the output stage of your opamp will cause current to flow
>through the power supply. If the power supply has a high impedance, this
current
>will be converted to a voltage and cause the supply to ripple synchronously to
>the opamp's output. If there's a lot of gain in the circuit, then you'll get an
>oscillator! (Don't ask how I know :).
>
>It's fairly straight forward to calculate the noise voltage that would be
>induced on your power supply leads due to the opamp switching.
.....

Hi Scott, thanks for your input. Yes, to all of your questions - re
PSRR and P/S source impedance. However, I wouldn't think the opamps
themselves [at least in my case] are responsible for creating much
P/S buss ripple, since they move a relatively small amount of current
- a few milliamps.

In general, putting .1 uF and 10-20 uF caps on v.reg high and low
sides is the usual way to lower P/S impedance. However, you are also
right about the "theory vs practice" thing. Caps are not ideal
devices, they have series R and L. And all leads/traces have
inductance. This is why they always say put the bypass caps as
close as possible to the Vcc/Vss pins.

But no matter how much bypassing you seem to have, and how small
1/(2*PI*F*C) may seem to be, you can always measure tons of hash
on digital busses - at least in my experience. And if the analog
busses pick up some of this noise, because they are on the same
pcb with the digital, run for inches and are inductive, and the
bypass caps aren't ideal, then you need good opAmp PSRR to help
deal with whatever pickup there is. PSRR = 20 dB [as in most std
opAmps at 1 Mhz] is only 10:1 rejection, so a mere 20 mV of buss
noise would translate into 2 mV of opAmp noise.

This is how I see the problem.
=============

>It's fairly straight forward to calculate the noise voltage that would be
>induced on your power supply leads due to the opamp switching. The 'filter
>capacitance' along with equivalent series resistance (esr) can be used to
>approximate the filter's impedance. If you look at the max current swing in
your
{Quote hidden}

As mentioned above, filtering is never perfect, since real caps aren't
perfect, plus all leads have some inductance. And correct, gnd is not
always gnd. So I guess the main solution here is to use wide traces,
physically separate analog and digital subsystems, don't track digital
lines over analog traces and gnds, and return the analog and digital
gnds separately to the power source with only a 1-point connection
between the two.

This last is interesting because some people say the 1-point
connection should be made at the power entry point, while others
say it should be directly under the A/D converter - ie, the place
where analog and digital meet - and that the analog currents should
be conducted thru the digital gnd plane, but via a physically
separate route than the high-frequency/high-current digital signals.
These things seem to be a little difficult to get a handle on.

best regards,
- Dan Michaels
Oricom Technologies
===================

2000\05\03@003146 by Dan Michaels

flavicon
face
Russell McMahon wrote:
.....
>I've attached some hopefully helpful comments from my colleagues.  who are
>expert in this area. As you will read, they are achieving results that would
>be very acceptable to you.
.......
>For reasons I won't go into the ADC is run quite fast with a (pk-pk
>noise-defined) resolution of about 15 bits and then additional filtering is
>done by the microcontroller which improves this to about 18 bits.  The
>filtered 24-bit result is updated internally at about 400Hz but is normally
>only read over the bus at about 20Hz.  Input bandwidth is around 10Hz under
>small-signal conditions, but large-signal transitions are tracked much more
>rapidly using the FASTStep feature of the AD7730 and supporting features in
>our own digital filtering.
>

Russell,

Thanks for going the extra distance and talking to your associate about
my problem. This entire thread has offered some really good advice for
successful application of 24-bit A/Ds. Unfortunately, the AD7730 won't
help me very much, since my system requires 1 Mhz BW, and the BW of
the 24-bit converters is a little too low - 10-50 hz. If I ever do get
into the 24-bit business, I'm going to come back and find this thread.
================
......
>Interestingly, during development, while we did not have any real problem
>with noise limiting usable resolution, we did have difficulty approaching
>the claimed drift figures for the AD7730 device.  The problem turned out to
>be due to high-frequency noise injection into the ADC front-end being
>aliased to very low frequencies which were indistinguishable from offset
>drift.
......

I find this observation pretty interesting. The front-ends of the
successive-approx A/Ds, like I use, tend to be quite wideband - the
LT1400 has a 400 Khz max samplg rate but 4 Mhz BW. So I think
aliasing of hi-freq pickup may be a problem - and I'm trying to
figure out how to deal with this other than just low-passing the
signal in. I don't have a drift problem, like your associate,
but hi-freq noise can still wrap around into the pass-band.

I found an article dealing with some of these issues, and am
perusing it:

"Attack the Noise Gremlins That Plague High-Speed ADCs"
http://www.elecdesign.com/magazine/1999/dec1799/analog/1217ao3.shtml

Best regards and thanks,
- Dan Michaels

2000\05\03@003155 by Dan Michaels

flavicon
face
Dave Van Horn wrote:
.....
>>Sounds like you could use some front-end RF filtering too. Maybe
>>ferrite beads in the input signal lines, or inductors in the Vcc
>>lines, etc.
>
>BTDT. None of that made a noticable difference without changing the op-amp.
>I'm going in again now, and re-evaluating all that in case it makes a
>difference, but it was too small to observe before.

I bet what fixed the problem is that the LMC6464 only has 50 Khz BW.
===============

>>And I've looked at dozens of op amp specsheets in the past couple
>>of days. Turns out all of the JFET types have very bad PSRR- at 1
>>Mhz, only 0 to 20 dB. Even true for Natl LM6152 which is 75 Mhz GBW.
>
>Use the best you can afford, and then fix as much as possible on the layout.
>RC filters specifc to the op-amp will help a lot, they will knock 1 MHz
>right down.
>Those Murata/Panasonic EMI filters are great down there, and cheap too $0.25.
>

Good suggestion, I've got just enough room to add these EMI
filters in the layout. So far, I've heard about 50 suggestions on
this thread, and about all of them are on the pcb now. I'm gonna
poop badly if the noise doesn't get any better after all this
wheel spinning :-).

cheers,
- Dan Michaels

'[OT] [EE] Motor Speed Control via PIC'
2000\05\03@094726 by Mark Peterson

flavicon
face
I'm trying to make a speed control for a whole house fan I purchased.  The
manufacturer warns in the instructions not to attempt to use a solid state
speed control device with the fan.  This brings up a couple questons.

1.  Firing a triac at various angles to regulate power to a device is
pretty straight forward.  Does the method used to do this vary depending
whether you're dealing with a resistive load versus a reactive load like an
induction motor?  Just how does motor speed control differ from a basic
lamp dimmer?

2.  What is the method to use to have a PIC control the speed of such a fan
motor?  I was thinking that I could vary the voltage on an analog input to
get a desired speed value in a register but then how to I get a
corresponding output from the PIC that will vary the firing angle of a
triac or something similar?  You may be asking why I want to use a PIC for
the speed control.  I'm already planning to use a PIC to control run time
of the fan, to perform a thermostat function, and to automatically open and
close the fan's shutters.  I'd like to go a little further and use it for
speed control as well.

Any ideas, comments, or warnings will be greatly appreciated.  Thanks so
much.

Mark

2000\05\03@100023 by Alan B Pearce

face picon face
It may be a style of motor which does not lend itself to speed control. If it is
a shaded pole motor, I understand that they run synchronous to the mains
frequency (with some slight slippage). How do you know if it is this type? Well
I have always known them to be the type used in small fans where there is a
laminated iron core with a winding on it, as well as one or two pairs of very
heavy copper shorted turns going through holes in the core.

'[OT] [EE] 24-bit A/D. Are We in the Twilite Zone H'
2000\05\03@114746 by Dan Michaels

flavicon
face
At 03:24 AM 4/29/00 -0700,  Tom Handley wrote:
........
>PSBS: I had more to say on the LTC2400 and Dennis' comments about
>`Think before you comment' and "Bit Jittering" which I assume meant
>"Dithering" which I don't think is practical at the sub uV level but
>I've been busy and I'll try to follow up...
>

Tom,

I've been itching to hear your comments on signal "jittering/dithering".

Andy Kunz mentioned in passing that he uses this technique, but did
not elaborate on how it was done or what kind of improvement he saw.

best regards,
- Dan Michaels
==============

2000\05\03@120052 by Andrew Kunz

flavicon
face
I haven't been following this thread, just opened this one on a lark.

Give me your fax and I'll send you a sketch of it later.  Maybe someone will
scan it and post it somewhere then.

Andy









Dan Michaels <oricomSTOPspamspamspam_OUTLYNX.SNI.NET> on 05/03/2000 11:41:51 AM

Please respond to pic microcontroller discussion list <spamBeGonePICLISTSTOPspamspamEraseMEMITVMA.MIT.EDU>








To:      KILLspamPICLISTspamBeGonespamMITVMA.MIT.EDU

cc:      (bcc: Andrew Kunz/TDI_NOTES)



Subject: Re: [OT] [EE] 24-bit A/D. Are We in the Twilite
         Zone Here?








At 03:24 AM 4/29/00 -0700,  Tom Handley wrote:
........
>PSBS: I had more to say on the LTC2400 and Dennis' comments about
>`Think before you comment' and "Bit Jittering" which I assume meant
>"Dithering" which I don't think is practical at the sub uV level but
>I've been busy and I'll try to follow up...
>

Tom,

I've been itching to hear your comments on signal "jittering/dithering".

Andy Kunz mentioned in passing that he uses this technique, but did
not elaborate on how it was done or what kind of improvement he saw.

best regards,
- Dan Michaels
==============

2000\05\03@120241 by Andrew Kunz

flavicon
face
Oh, and it easily adds bits.  I do 256 samples and get 2-3 bits more GOOD data,
usually more (depends on what it's measuring) up to 4 bits.

Andy

2000\05\03@122316 by Alice Campbell

flavicon
face
Dan:
Think of it as the opposite of averaging data. to average,
shift right and get twice the number of samples.  To jitter,
shift left one space and add 1 bit randomly + or - to each
one.  Suddenly duplicate numbers slide off the top of one
another.  Particularly useful for plotting data or making
sounds,the blurry data is actually more usable than the
original.

alice


{Quote hidden}

2000\05\03@123942 by jamesnewton

face picon face
I don't understand "duplicate numbers slide off the top of one another".

I also can't see how this jittering could have any positive effect. I could
understand shifting it one bit left and then average with previous
readings... The random extra bit makes the reading #.5 rather than #.0. Is
that what we are talking about?

---
James Newton (PICList Admin #3)
EraseMEjamesnewtonspamEraseMEpiclist.com 1-619-652-0593
PIC/PICList FAQ: http://www.piclist.com or .org

{Original Message removed}

2000\05\03@134114 by David VanHorn

flavicon
face
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1


>I bet what fixed the problem is that the LMC6464 only has 50 Khz Bw

Almost sorta.
I had limited the other amp to well below that with external RC, and was
unable to get rid of the problem. Actually, I was unable to affect it
significantly.  The 6464 dosen't exhibit the rectification problem at all.
This is definitely a situation where the opamp is rectifying ambient RF
into noise on my signal.


- --
Are you an ISP?  Tired of spam?
http://www.spamwhack.com  A pre-emptive strike against spam!

Where's Dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9

-----BEGIN PGP SIGNATURE-----
Version: PGPfreeware 6.5.2 for non-commercial use <http://www.pgp.com>

iQA/AwUBORB+SIFlGDz1l6VWEQIJfQCguR3NpPb2xEc2EVLPqEae4Wxs0zMAnA1t
JakZzq3aTpmZTSwVTNFyE+aD
=S9Nf
-----END PGP SIGNATURE-----

2000\05\03@155513 by jamesnewton

face picon face
<BLOCKQUOTE AUTHOR="Alice">This refers to GRAPHING the numbers</BLOCKQUOTE>

<BLOCKQUOTE AUTHOR="Andy">Xunknown + Noise = Xreal (more closely,
anyway)</BLOCKQUOTE>

Ok, kids. Which is it? <GRIN>

Specifically, I understand Alice's point but is Andy talking about averaging
data or what? How else can an Xunknown be made more Xreal with noise?

Also, doesn't adding a "third dimension to the graph" have the same effect
as averaging during the time that the Xunknown is at that point? in that it
makes it clear that X was REALLY at this point for a while.

---
James Newton (PICList Admin #3)
@spam@jamesnewton@spam@spamspam_OUTpiclist.com 1-619-652-0593
PIC/PICList FAQ: http://www.piclist.com or .org

{Original Message removed}

2000\05\03@162042 by Scott Dattalo

face
flavicon
face
On Wed, 3 May 2000, James Newton wrote:

> <BLOCKQUOTE AUTHOR="Alice">This refers to GRAPHING the numbers</BLOCKQUOTE>
>
> <BLOCKQUOTE AUTHOR="Andy">Xunknown + Noise = Xreal (more closely,
> anyway)</BLOCKQUOTE>
>
> Ok, kids. Which is it? <GRIN>
>
> Specifically, I understand Alice's point but is Andy talking about averaging
> data or what? How else can an Xunknown be made more Xreal with noise?
>
> Also, doesn't adding a "third dimension to the graph" have the same effect
> as averaging during the time that the Xunknown is at that point? in that it
> makes it clear that X was REALLY at this point for a while.
>

I believe that what they're saying is that at long as your A2D converter has
fairly stable transitions that you can add 'noise' to the signal, then you can
filter the noisy signal obtain a more accurate representation of the 'real'
signal. You can imagine a similar effect without noise. Suppose you have at your
disposal a saw-tooth wave form that varies in amplitude by an amount equal to
say one count of your A/D converter. Now further suppose that your able to
precisely add this to your unknown signal. If you poll the A/D converter while
you apply the triangle wave and measure how long it takes for the A/D converter
to increment, you can calculate how far between the quantized voltages that your
signal is.

This is wonderful in theory, but in practice it ain't so easy. For one, the
signal under test varies. You could add an additional sample and hold circuit in
front of the A/D but why add the cost (and [uncontrolled] noise)? However, if
you add a controlled noise source to the signal you can achieve the same
results as you can with the theoretically perfect saw tooth waveform. The idea
is that the random noise will cause the signal to bounce around and cross
several of the quantized voltage levels. The only thing you need to do is low
pass filter (i.e. average) the consecutive samples to achieve the more accurate
reading.

I can imagine a simple example where the controlled noise varies by 2 A/D
counts. If you measured your signal without the noise you'll get a count of
X. If you add the noise, your signal will vary between X-1, X, and X+1. If more
readings were obtained in the X+1 bin than the X-1 bin, then you can say that
the original 'X' value is between X+0.5 and X+1. This is essentially one more
bit of information. And certainly a longer average over many samples will
improve the estimate. (But you'll still need to take into account your varying
signals...)

Scott

'[OT] [EE] Motor Speed Control via PIC'
2000\05\03@170557 by l.allen

picon face
Mark Wrote...

> I'm trying to make a speed control for a whole house fan I purchased.  The
> manufacturer warns in the instructions not to attempt to use a solid state
> speed control device with the fan.  This brings up a couple questons.
>
> 1.  Firing a triac at various angles to regulate power to a device is
> pretty straight forward.  Does the method used to do this vary depending
> whether you're dealing with a resistive load versus a reactive load like an
> induction motor?  Just how does motor speed control differ from a basic
> lamp dimmer?
>
> 2.  What is the method to use to have a PIC control the speed of such a fan
> motor?
>
> Any ideas, comments, or warnings will be greatly appreciated.  Thanks so
> much.
>

A shaded pole motor (most fans) is a synchronous
motor, it turns at a speed close to a function of its poles
and the mains frequency, with some slippage.
The proper way to vary its speed is to vary the mains
frequency. This is also true of 3 phase and other
induction motors of various types.
Needles to say varying the power frequency is a bit of a
challenge and not a task for youre average beginner.

Simply altering the phase angle (triac etc type switching)
will at best simply cause more and more slippage with a
huge drop in efficiency but more likely lead to burnt
motors as the turning of the motor normally limits the
current flowing through it (cutting flux and all that) and a
slowing or stopping of the motor will cause destructive
currents to flow.
The only AC motors that respond to triac (and other
switching) speed control are universal motors like those
used in handrills and small appliances etc. They are a
kind of DC motor with a commutator (the commutator is
the give away to what kind of motor it is) and their speed
is related to the current flowing through the windings.

There was discussion on the PICLIST a while ago on
simple , rather rough, speed control of a shaded pole
motor by skipping cycles.
This might be worth an experiment (I have NOT done this)
and should avoid (no guarantees!!!!!) the old motor burn
out problems.

What that means is the PIC detects zero-crossings and
will fire a triac at the beginning of that cycle and the
conducting triac will remain on (by virtue of its inherent
operation) until the next zero crossing.
As there are two zero crossings per cycle.. It would be
best to have a minimum of 2 so a full AC wave is fired.
Now I would have a 'duty cycle' of waves fired to waves
not... say a pattern of 10 where 10% would be 9 cycles
fired to 1 off, 20% 8:2, 30% 7:3 etc.

BUT do not let the motor stall or go very slow as you will
be in a situation where the motor is constantly in
"starting' condition which might cause overheating.

This technique (cycle skipping) is called 'burst firing' and
will work with resistive loads like heaters and other
thermaly slow devices (a light bulb will flicker at lower
settings).
The really BIG advantage of burst fire is its really low EM
emissions, often NO or little suppression is needed on
the mains feed.

WARNING.. these voltages are very dangerous, all PIC
interfaces should be isolated and explosive component
damage can result from incorrect component selection or
application.




_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

'[OT] [EE] 24-bit A/D. Are We in the Twilite Zone H'
2000\05\03@175025 by Plunkett, Dennis

flavicon
face
In this case your attempting to average out the LSB. Note that this is only
an advantage as the noise is nominaly equivalent to the LSB. While on this
matter we must also consider the noise source. In an ADC the noise generated
is ((1/root 12) * the LSB) (Noise typically has peeks 6 to 8 times the
average!) so this is the base noise floor of the ADC (General term). From
this we can see if the noise on the signal is greater than or less than
(Remember that noise is adative not subtractive)
Back to the original LSB stuff.
What we are attempting to do is to find the LSB value. Note that the ADC
qunatizes the sample so that it is to the next lowest LSB value. Thus if tou
are .1LSB lower then the result will be 0.1LSB less, however normal rounding
would consider this as 1LSB more!



Dennis




> {Original Message removed}

2000\05\03@201940 by Brandon, Tom

flavicon
picon face
>From what I've read dithering is most appropriate on slow moving signals.
Imagine you have a 4bit ADC with a slow moving analog input of 1-16units.
The inputs at say 8.4, you sample it, and get 8. Sample again, 8 again. You
sample 50 times, nothing but 8's, all you know is it's between 8 and 9. Now,
imagine there's noise (say 3LSB p-p (I believe this is somewhere around
1\2LSB noise power)) while you take your 50 measurements. Over those 50
measurements, with the possible 3 LSB's noise you now get values ranging
from say 5 to say 11. Average it out and you should (if the noise is
"random") get about 8.4. Et voila, increased accuracy. If you actually add
known noise you can get even better rsults by then subtracting the added
noise. But, why add noise when you couldn't get rid of it if you tried.

Tom.

{Original Message removed}

'8051 Programmer ? [OT] [EE]'
2000\05\03@204854 by Sebastian Garcia

flavicon
face
Hi all!

I'm looking for a *Very Simple* programmer for the 8051's series of flash
MCU's (Atmel, Dallas, Analog Devices, etc).

Any links are welcome!

TIA,

S.-

'[OT] [EE] Motor Speed Control via PIC'
2000\05\04@013642 by Vasile Surducan

flavicon
face
On 3 May 00, at 8:44, Mark Peterson wrote:

> I'm trying to make a speed control for a whole house fan I purchased.  The
> manufacturer warns in the instructions not to attempt to use a solid state
> speed control device with the fan.  This brings up a couple questons.
>
> 1.  Firing a triac at various angles to regulate power to a device is
> pretty straight forward.  Does the method used to do this vary depending
> whether you're dealing with a resistive load versus a reactive load like an
> induction motor?  Just how does motor speed control differ from a basic
> lamp dimmer?

Mark,

   AC  brushless motors have a non-linear response between supply
and speed, it's like a 220V lamp supplied from 180V to 220V, the
effect is negligible...a good but expensive choice is to modify supply
frequency...
       Asimple solution is to use a DC brush motor and to modifie with
a triac (thyristor and bridge, or transistor ) the efective amplitude of
supply, using a PWM algorithm.
Vasile
*********************************************
Surducan Vasile, engineer
mail: spamBeGonevasilespamKILLspaml30.itim-cj.ro
URL: http://www.geocities.com/vsurducan
*********************************************

'[OT] [EE] 24-bit A/D. Are We in the Twilite Zone H'
2000\05\04@015521 by Tom Handley

picon face
  Dan, I see Scott and Tom have explained dithering in detail. My point
was, using the LTC2400 at full resolution (24-Bits), I don't see where
you can get a good controlled noise source. I think the confusion here
is that I'm refering to a specific device which also has 4 sub-LSBs
that you can use for averaging. Sorry for the confusion. I'm guilty
of moving your original question to LTC2400-specific info...

  - Tom

At 09:41 AM 5/3/00 -0600, Dan Michaelsyou wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

2000\05\04@061621 by Kbek Tony

flavicon
face
Hi,
I'm intrigued by this discussion, and I'm probably
in over my head here :-)
Anyway regarding bit jittering, increasing accuracy etc.
If I understand correctly if one adds a random bit to the
reading then one possibly ( likely ? ) could increase the accuracy ?
Is this vaild for, let's say one has 6 bit's of noice ?
Would one then add several random bit's ?
Ore are this only valid for the LSB ?

Further how does one accomplish this 'random bit' ?
to be truly random I guess it would be very hard,
I've read the last month disscussion regarding
an random byte generation, but for a single bit
there must be an easier way.

Anyway very interesting thread, nice to read.

BTW Just 'playing' with the 24 bit AD7730 ;-) DS


/Tony



Tony KŸbek, Flintab AB            
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E-mail: .....tony.kubekspam_OUTspamflintab.com
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'[EE] ISD & other voice chips'
2000\05\04@090935 by Hardware Engineering

picon face
I've saved some posts about interfacing to the ISD chips, but has anyone used
any other devices that are similiar - or better should I ask if there are any
others that are like these?

Application I am think of, need to address 5 groups of 10 second interval
voice storage.  In other words, 5 switches select what interval to be played.
10 seconds is a basic guess...ie...if its a 60 second device, I will chop it
into 12 second intervals.

____________________________________________________________________
Get free email and a permanent address at http://www.netaddress.com/?N=1

'[OT] [EE] 24-bit A/D. Are We in the Twilite Zone H'
2000\05\04@124420 by jamesnewton

face picon face
Correct me if I'm wrong, but the noise for the system that Scott is talking
about has to be added BEFORE the signal is "quantized" from analog to
digital. After, the extra fractional information is already lost. So
shifting the A2D result one bit left and adding a random bit would not
improve your resolution.

Again, the only reason I can see for shifting one bit left and adding a
random bit would be A) in combination with averaging and B) to make the *2
into a *2 + 0.5. And I really don't see the need for B. As an example: lets
say you have an XUnknown (XU) of 8.5 and are adding random noise (RN)
between 0 to 1. Your A2D only measures units of 1 (IN). This gets shifted
left one (*2) and added to the average (+A) which is then shifted left one
(/2) and, if you had floating point divide, you would be able to read this
as having an extra bit of precision past the actual input value. (OUT)

 ANALOG  |         DIGITAL
XU      RN      IN      *2      "+A     /2      OUT
                                       0
8.5     0.5     9       18      18      9.00    4.5
8.5     1       9       18      27      13.00   6.5
8.5     0.5     9       18      31      15.00   7.5
8.5     0       8       16      31      15.00   7.5
8.5     0.5     9       18      33      16.00   8
8.5     1       9       18      34      17.00   8.5
8.5     0.5     9       18      35      17.00   8.5
8.5     0       8       16      33      16.00   8
8.5     0.5     9       18      34      17.00   8.5
8.5     1       9       18      35      17.00   8.5
8.5     0.5     9       18      35      17.00   8.5
9       0       9       18      35      17.00   8.5
9       0.5     9       18      35      17.00   8.5
9       1       10      20      37      18.00   9
9       0.5     9       18      36      18.00   9
9       0       9       18      36      18.00   9
9       0.5     9       18      36      18.00   9
9       1       10      20      38      19.00   9.5
9       0.5     9       18      37      18.00   9
9       0       9       18      36      18.00   9
9       0.5     9       18      36      18.00   9
9       1       10      20      38      19.00   9.5
4.7     0.5     5       10      29      14.00   7
4.7     0       4       8       22      11.00   5.5
4.7     0.5     5       10      21      10.00   5
4.7     1       5       10      20      10.00   5
4.7     0.5     5       10      20      10.00   5
4.7     0       4       8       18      9.00    4.5
4.7     0.5     5       10      19      9.00    4.5
4.7     1       5       10      19      9.00    4.5
4.7     0.5     5       10      19      9.00    4.5
4.7     0       4       8       17      8.00    4
4.7     0.5     5       10      18      9.00    4.5


Let me know if anyone wants the Excel spreadsheet used to make that.

Note that the averaging is absolutely necessary and has the effect of
reducing the maximum frequency that can accurately be sampled by a factor of
4 or so. You can get around that (at the cost of momentary loss of some
accuracy) by tossing the average (over writing it) when the input changes by
more than 1 from its previous value. Better yet, compute the delta between
the last reading and this, and divide the average by it, multiply the new
value by it before averaging so that small changes have no effect but large
changes quickly overcome the average.

Now, if the random noise was between -0.5 and +0.5 and you wanted an exact
result rather than just a more accurate proportional result, you would need
to add .5 in somewhere either by adding a 1 after the *2 every other time or
by just adding .5 to the OUT.

But there just isn't any reason to add digital noise to an a2d result (other
than graphing).

Right?

---
James Newton (PICList Admin #3)
TakeThisOuTjamesnewton.....spamTakeThisOuTpiclist.com 1-619-652-0593
PIC/PICList FAQ: http://www.piclist.com or .org

{Original Message removed}

2000\05\04@131045 by Andrew Kunz

flavicon
face
James,

What we would do is measure an analog signal using the time-honored cap/res
delay time with a PIC.  Our time was typically 10-50, where our signal was
acquired (sample-and-hold setup).

Then we would add a random number to this in the range 0-15.  The random number
could come from any of a number of places; ours was the CRC of the last message
we received (we were continuously receiving messages).

These results were then continuously averaged (Avg = ((sum of samples) - Avg) +
newsample).

The result was surprisingly accurate.

Andy

PS.  To whomever I was going to fax yesterday, never mind.  The above is what I
really wanted to show you.

'[OT][EE] PCMCIA (PC CARD) data xfer to laptop'
2000\05\04@131249 by jamesnewton

picon face
Does anyone know of a ready made embedded PCMCIA (PC CARD) writer that can
write a format readable in the standard PC (laptop) like it was a drive?

I have a friend who needs to instantly transfer mega-bytes of data to a
standard laptop.

---
James Newton TakeThisOuTjamesnewtonKILLspamspamspamgeocities.com 1-619-652-0593
http://techref.massmind.org
All the engineering secrets worth knowing

'[OT] [EE] 24-bit A/D. Are We in the Twilite Zone H'
2000\05\04@133326 by Scott Dattalo

face
flavicon
face
On Thu, 4 May 2000, Andrew Kunz wrote:

> James,
>
> What we would do is measure an analog signal using the time-honored cap/res
> delay time with a PIC.  Our time was typically 10-50, where our signal was
> acquired (sample-and-hold setup).
>
> Then we would add a random number to this in the range 0-15.  The random number
> could come from any of a number of places; ours was the CRC of the last message
> we received (we were continuously receiving messages).
>
> These results were then continuously averaged (Avg = ((sum of samples) - Avg) +
> newsample).
>
> The result was surprisingly accurate.

James, now I know why you were confused. I have to admit that after Andy's
explanation I'm confused as well. First a couple of questions which Andy may
wish to answer. When you say 'time was typically 10-50', what does that
mean? 10-50 milliseconds, 10-50 samples per second? Are you sure that the
formula is correct? (There's a scaling factor missing.)

I suspect if you go back and repeat your experiments with the "digital random
number" stuff removed that you'll get the same results - perhaps even improved
results. From the information you've provided, I can confidently assert that
adding this digital noise is of no beneficial value whatsoever. Instead, the
averaging algorithm removes the random variations in the REAL analog signal
along with the digital variations that were artificially added. Theory aside,
let's look at it practically. If your A/D converter is absolutely solid and
your signal contains no noise, then you'll get the same value everytime you read
the A/D (assuming a DC input of course). The information from the A/D is
constant. There's nothing you can do to increase the information content. If you
add a random value that has a mean of zero, this is not going to affect the A/D
result.


Scott

2000\05\04@135750 by Andrew Kunz

flavicon
face
We were measuring an RF signal with a high noise component (0-15 was reasonable,
ie, 160% noise on 100% signal!)

The 10-50 was counts; I don't have the formula which converted counts to dBmV.

It worked much better than w/o the noise correction.

Andy









Scott Dattalo <.....scottspamRemoveMEDATTALO.COM> on 05/04/2000 01:32:11 PM

Please respond to pic microcontroller discussion list <RemoveMEPICLISTspamspamBeGoneMITVMA.MIT.EDU>








To:      spamBeGonePICLIST@spam@spamspam_OUTMITVMA.MIT.EDU

cc:      (bcc: Andrew Kunz/TDI_NOTES)



Subject: Re: [OT] [EE] 24-bit A/D. Are We in the Twilite
         Zone Here?








On Thu, 4 May 2000, Andrew Kunz wrote:

> James,
>
> What we would do is measure an analog signal using the time-honored cap/res
> delay time with a PIC.  Our time was typically 10-50, where our signal was
> acquired (sample-and-hold setup).
>
> Then we would add a random number to this in the range 0-15.  The random
number
> could come from any of a number of places; ours was the CRC of the last
message
> we received (we were continuously receiving messages).
>
> These results were then continuously averaged (Avg = ((sum of samples) - Avg)
+
> newsample).
>
> The result was surprisingly accurate.

James, now I know why you were confused. I have to admit that after Andy's
explanation I'm confused as well. First a couple of questions which Andy may
wish to answer. When you say 'time was typically 10-50', what does that
mean? 10-50 milliseconds, 10-50 samples per second? Are you sure that the
formula is correct? (There's a scaling factor missing.)

I suspect if you go back and repeat your experiments with the "digital random
number" stuff removed that you'll get the same results - perhaps even improved
results. From the information you've provided, I can confidently assert that
adding this digital noise is of no beneficial value whatsoever. Instead, the
averaging algorithm removes the random variations in the REAL analog signal
along with the digital variations that were artificially added. Theory aside,
let's look at it practically. If your A/D converter is absolutely solid and
your signal contains no noise, then you'll get the same value everytime you read
the A/D (assuming a DC input of course). The information from the A/D is
constant. There's nothing you can do to increase the information content. If you
add a random value that has a mean of zero, this is not going to affect the A/D
result.


Scott

2000\05\04@141852 by Andrew Warren

face
flavicon
face
Andrew Kunz <TakeThisOuTPICLISTspamspamMITVMA.MIT.EDU> wrote:

> What we would do is measure an analog signal using the
> time-honored cap/res delay time with a PIC. .... Then we would add a
> random number to this in the range 0-15.
>
> These results were then continuously averaged (Avg = ((sum of
> samples) - Avg) + newsample).
>
> The result was surprisingly accurate.

Andy:

I haven't read any of the previous messages in this thread, so I may
be WAY off-base here... But adding random noise AFTER the A/D
conversion (i.e., adding DIGITAL noise) doesn't give you any more
information than you'd have if you just left the signal alone.  If
you're trying to increase the resolution of your conversion by
dithering, you need to do that BEFORE the conversion, by adding
ANALOG noise.

As I said, I'm not sure what the exact point of the discussion is, so
please ignore this if you were talking about something other than
dithering the signal to achieve higher resolution.

-Andy


=== Andrew Warren - fastfwdEraseMEspamix.netcom.com
=== Fast Forward Engineering - San Diego, California
=== http://www.geocities.com/SiliconValley/2499

2000\05\04@143327 by Andrew Kunz

flavicon
face
I had nothing to do with the algorithm other than coding it.

There may have been something about the designer's concept that isn't here,
mainly because I didn't need to understand the concept.

Andy

2000\05\04@150723 by Andrew Warren

face
flavicon
face
Andrew Kunz <RemoveMEPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU> wrote:

> I had nothing to do with the algorithm other than coding it.
>
> There may have been something about the designer's concept that isn't
> here, mainly because I didn't need to understand the concept.

Hmm... Maybe adding the digital noise made that pseudo-average
algorithm converge faster?  I'd have to think about it for a bit;
maybe Scott Dattalo can answer more quickly.

-Andy


=== Andrew Warren - @spam@fastfwdRemoveMEspamEraseMEix.netcom.com
=== Fast Forward Engineering - San Diego, California
=== http://www.geocities.com/SiliconValley/2499

'[OT][EE] PCMCIA (PC CARD) data xfer to laptop'
2000\05\04@165659 by Mark Willis

flavicon
face
I do this ALL the time - Lots of good answers for this one, James;  Buy
a SanDisk (or Delkin, or Simple Tech., or or <G>) PCMCIA Flash card
(either Compact Flash with an adapter if needed, or a PCMCIA Type II
Flash Card) - install that into a unit like an SCM SwapBox (eBay has 'em
all the time - I have a spare, could ship it to you if you'll replace it
with a good unit.)  $35 should get you one.

search-desc.ebay.com/cgi-bin/texis/ebaydesc/results.html?query=scm+swapbox&dest=&cobrandpartner=x&SortProperty=MetaEndSort&SortOrder=&maxRecordsPerPage=&srchdesc=y&category0=&category1=&category2=&category3=&textonly=n&tc=&ht=1&st=&minPrice=&maxPrice=&ebaytag1=&ebaytag1code=&ebaycurr=&psURLSaveMethod=PersonalShopperSaveSearch&userid=&pass=&psreg=&psfreq=&psdura=
gives 10 hits <G>

I like these as the upper slot will handle a Type III HDD - can stack
that atop a Type II card and transfer data easily.

Other co's make these as well, in differing varieties too (DataBook has
a Parallel Port unit that's not bad - get the later one if you go with
those, TMD-650 or newer.)

Definitely check h/w and s/w requirements on the unit you plan to get
(the earlier ISA SCM's need an IRQ for the board, newer one's don't,
also these need one add'l IRQ for most installed cards.)

Another answer:  Get a NIC card (or parallel port NIC) for your laptop -
Pull the data down to the laptop's HDD, then transfer it onto the PCMCIA
Card if you still need to do that (may be able to do this directly if
you set it up right.)

Also, SRAM cards are pretty nice (leave them plugged into some power
source i.e. powered-up desktop when not in use, or yank the battery, as
otherwise the battery eventually dies from the slow drain of the card;
Flash cards are LOTS less pricey, though, an SRam 4Mb card costs the
same as a 175Mb Flash card roughly.

You'll usually need to initialize either card (CF / Flash or SRAM) -
sorta like "FDisk" for these media.

BTW: "instantly"??!?  <VBG>

 Mark

James Newton wrote:
{Quote hidden}

--
I re-ship for small US & overseas businesses, world-wide.
(For private individuals at cost; ask.)

2000\05\04@171554 by jamesnewton

face picon face
I wasn't clear enough... I need to be able to write to this thing from a PIC
in a remote device. Megabytes of data. Then pick it up, pull the card
(Compact Flash, SanDisk, PCMCIA FLASH, whatever), push it into the Laptop,
copy the file or files to hard drive, erase, reinsert into device and leave.

Critical points:
A) ultra fast transfer speed. 16 Meg in several seconds.
B) standard unaltered laptop and no fancy software.
C) multi-meg storage ability.
D) fairly low power. will only fire up briefly, capture data, then shut down
so can't be ram or hard drive.

Basically, if I could buy that part of a digital camera...

---
James Newton @spam@jamesnewtonspam_OUTspam.....geocities.com 1-619-652-0593
http://techref.massmind.org
All the engineering secrets worth knowing

{Original Message removed}

2000\05\04@182934 by Mark Willis

flavicon
face
Aah.  For the connectors, DigiKey sells both PCMCIA and CF sockets (68
or 50 pins respectively, 0.050" pin spacing, two rows 0.050" CTC.)

You'll need PIC Code to handle reading/writing the FAT16 / directory /
file structure, know people working on that but none done yet.  Several
doing this on Atmel's.  One has FDD code on an 8051 that was working for
a commercial product (he's moved & not back on here yet, I guess.  He'll
get settled in.)

Another option:  Could just swap media when you visit the remote site
(then read speed's not so critical - if you're trying to keep a constant
log,  you might consider doing *something* to prevent a write from
occuring as you remove the card - don't want to corrupt any data.

I've found one rather decent URL for you, and a few others:

http://www.rdrop.com/~cary/html/pc_card_faq.html  PC Card FAQ
115k of good data, should help.  (I need to read that again.)

Also,
http://hwb.acc.umu.se/index.html (The Hardware Book) has lots of
connectors, http://hwb.acc.umu.se/co_PcCard.html,
http://hwb.acc.umu.se/co_PcCardAta.html, and
http://hwb.acc.umu.se/co_CompactFlash.html specifically would be germane
<G>

(http://www.programmersheaven.com/zone5/cat20/index.htm has a bunch of
old good ASM (for 80x86 machines) routines, if the Linux sources don't
tell you what you want to know.)

I have lots of old AT/XT BIOS books etc. so if you need to know
something I can look it up...

 Mark

James Newton wrote:
{Quote hidden}

> {Original Message removed}

'[OT] [EE] 24-bit A/D. Are We in the Twilite Zone H'
2000\05\04@203718 by Brandon, Tom

flavicon
picon face
In regards to adding more noise, remember, you're not actually adding any
accuracy (repeatability), in fact you're decreasing the accuracy of the
individual readings as succesive readings of the same value (without noise)
will have more variation. What you are doing is adding precision. The
averaged result is now closer to the 'true' value.

However, I think this would only apply with analog noise. You need
fractional noise or it falls apart. Adding 1LSB of digital noise would just
give you 1\3rd correct values, 1\3rd up 1 LSB and 1\3rd down 1LSB (assuming
true Gaussian noise). Average that out and it just returns the correct
value.

Yes, averaging the values would reduce the noise. If it's natural noise then
it's Gaussian, thus it should average out to 0 over multiple samples. But
the digital noise is irrelevant. Assuming the digital noise is also Gaussian
it too will be averaged out, but it will not increase accuracy or precision
(but as suggested it may speed the averaging).

In terms of how you 'add' the random noise, you don't. Ever designed a
(mixed signal) circuit with 0 noise? You don't add analog noise, you just
use the existing noise (assuming it's Gaussian, which almost all naturally
occuring noise is). You could digitally produce the noise and then subtract
it out for even better accuracy but this is rarely used as it isn't
justified. After spending 6months trying to eliminate the #$%$ing analog
noise, it's nice to be able to put it to good use.

In terms of digitally producing Gaussian noise, you just apply the Central
Limits Theroem. It states that:
A sum of random numbers becomes normally distributed as more and more of the
random numbers are added together. The Central Limit Theorem does not
require the individual random numbers be from any particular distribution,
or even that the random numbers be from the same distribution.

This is why Gaussian noise is so common. Whenever multiple random processes
(any distribution including pseudorandom computer generated numbers)
interact, the overall output will show Gaussian distribution.

Tom.

-----Original Messages-----

>From Andy:
<SNIP>
It worked much better than w/o the noise correction.

Andy

>From Scott:
<SNIP>
I suspect if you go back and repeat your experiments with the "digital
random
number" stuff removed that you'll get the same results - perhaps even
improved
results.
<SNIP>

Scott

>From KŸbek Tony:

Hi,
I'm intrigued by this discussion, and I'm probably
in over my head here :-)
Anyway regarding bit jittering, increasing accuracy etc.
If I understand correctly if one adds a random bit to the
reading then one possibly ( likely ? ) could increase the accuracy ?
Is this vaild for, let's say one has 6 bit's of noice ?
Would one then add several random bit's ?
Ore are this only valid for the LSB ?

Further how does one accomplish this 'random bit' ?
to be truly random I guess it would be very hard,
I've read the last month disscussion regarding
an random byte generation, but for a single bit
there must be an easier way.

Anyway very interesting thread, nice to read.

BTW Just 'playing' with the 24 bit AD7730 ;-) DS


/Tony



Tony KŸbek, Flintab AB            
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
E-mail: tony.kubekspamBeGonespamflintab.com
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ

'[OT][EE] PCMCIA (PC CARD) data xfer to laptop'
2000\05\04@211137 by Byron A Jeff

face picon face
On Thu, May 04, 2000 at 02:14:03PM -0700, James Newton wrote:
> I wasn't clear enough... I need to be able to write to this thing from a PIC
> in a remote device. Megabytes of data. Then pick it up, pull the card
> (Compact Flash, SanDisk, PCMCIA FLASH, whatever), push it into the Laptop,
> copy the file or files to hard drive, erase, reinsert into device and leave.
>
> Critical points:
> A) ultra fast transfer speed. 16 Meg in several seconds.
> B) standard unaltered laptop and no fancy software.
> C) multi-meg storage ability.
> D) fairly low power. will only fire up briefly, capture data, then shut down
> so can't be ram or hard drive.
>
> Basically, if I could buy that part of a digital camera...

You can. Just spent a few minutes reading up on CompactFlash for a future
MIDI sequencer project. Basically CF is a flash memory with an embedded
controller that makes it look very much like an IDE device. In fact it has
what's called True-IDE mode that makes it look exactly like a minature IDE
disk. You read/write the disk using the 8 byte IDE task file and the 16 bit
dta bus. The bus can programmatically be reduced to an 8 bit bus if you need
to conserve pins.

Your project would have to maintain a DOS filesystem with a 12 bit FAT. This
limits your filesystems to 32MB but I'm sure you can live with that. Dave
Dunfield has a sample 12bit FAT implementation in C in this file:

ftp://ftp.dunfield.com/embedpc.zip


As for power consumption it seems to be quite small in standby but can grow
up to 90ma a pop when writing. You can probably conserve simply by buffering
512 bytes of data in RAM then writing a whole sector when full.

Interface to the PC is dead dumb simple. Plug in with a CF to PC-Card adapter,
slide into the PC-Card port, treat as a hard disk.

One caveat about True-IDE mode. It does require power-cycling the card to
set this mode as it's detected on power-up. So you need a way to power-cycle
the CF when you remove it.

Take a look here for an Hitachi CF family that has all of the relavent
specifications:

http://semiconductor.hitachi.com/products/product_abstract.cfm?p_id=895

Also Digikey has the 50 pin connectors for CF.

It looks like the winner to me.

BAJ
>
> ---
> James Newton RemoveMEjamesnewton@spam@spamspamBeGonegeocities.com 1-619-652-0593
> http://techref.massmind.org
> All the engineering secrets worth knowing
>
> {Original Message removed}

'[OT] [EE] 24-bit A/D. Are We in the Twilite Zone H'
2000\05\04@211346 by Scott Dattalo

face
flavicon
face
On Thu, 4 May 2000, Andrew Warren wrote:

> Andrew Kunz <.....PICLIST@spam@spamEraseMEMITVMA.MIT.EDU> wrote:
>
> > I had nothing to do with the algorithm other than coding it.
> >
> > There may have been something about the designer's concept that isn't
> > here, mainly because I didn't need to understand the concept.
>
> Hmm... Maybe adding the digital noise made that pseudo-average
> algorithm converge faster?  I'd have to think about it for a bit;
> maybe Scott Dattalo can answer more quickly.

I can't see how it'd possibly converge more quickly. If you view the average
operation as a low pass filter and assume that the noise is 'white' (that is, it
has energy at all frequencies) then there will be noise present right up to the
filter's cutoff. If you had a sine wave with a frequency close to the filter's
cutoff, you'd notice that the filter would let some of it through. I think the
same would be true here as well. In other words, I think it would take LONGER to
settle. Now the noise is not truely white since its DC component is absent
(presumably - otherwise you're just adding an error to the signal). The reason
this scheme works in the analog domain so well is that 1) the noise is (or
should be) absent of a any DC component 2) the low pass filter bandwidth is so
low that the amount of energy in the noise over that frequency band is
negligible.

>From this observation it's clear to conclude that adding random noise only works
well if the averaging filter or low pass filter has a very low frequency
cutoff. If you were to use this technique to acquire higher bandwidth data like
acoustical data, this technique would reduce the digitization accuracy. However,
if noise is added in a frequency band beyond the frequency at which your signal
resides, you may again apply these concepts. In this case it will become
necessary to over-sample the data, low-pass filter it, and then decimate it to
the sample rate you would have sampled without using this technique.

Perhaps a simpler approach would be to add a known error signal to your analog
signal. This signal could be sine wave or triangle wave with frequency just
outside the frequency of the signal of interest. Satisfy Nyquist for this known
analog signal (by sampling at 2 or 3 times the frequency of the sine or triangle
wave), then digitally subtract it out, and low pass filter the result. The idea
is that +1 -1 = 0, only the addition is analog and the subtraction is digital.
Now, the digitized sine wave subtracted from the sampled signal needs to have
more resolution than just one bit of your A/D converter other wise you wouldn't
benefit from the dithering.

Caveats - of course I've never tried this, but in theory...

Scott

2000\05\05@071308 by Peter L. Peres

picon face
Hi,

wrt. Andy Kunz's adding digital noise: I think that I know what is on.

He said that he has a very poor S/N at the input. I infer that he tried to
obtain a steady readout of the average RF level measured while receiving
modulated (AM ? - he does not say) rf signals. For this, he needed to
smooth the input somehow, to obtain something resembling RMS. By adding
'fast' noise I think that he faked oversampling, and then averaged the
result. This would be a median filter, done otherwise, imho. He also said,
that 'the result was surprisingly accurate' which means that he was
measuring the same signal also using other means, which means for RF are
either a specan or a rf milivolt/miliwattmeter. All three devices read out
RMS integrated over some time unless set up otherwise (i.e. peak or
instant power etc).

am I way off ?

Peter

2000\05\05@073422 by Andrew Kunz

flavicon
face
WOW, now that makes sense.

The signal was FM/FSK on a TV cable, with our carrier too close to Channel 2.

The "standard" was a SAM-II meter which measures signal level in dBmV.  Standard
equipment for cable TV.

The goal was averaged signal level, not instantaneous.

Glad somebody knew what I was talking about - I sure don't!

Andy









"Peter L. Peres" <.....plpRemoveMEspamACTCOM.CO.IL> on 05/04/2000 06:46:38 PM

Please respond to pic microcontroller discussion list <.....PICLISTSTOPspamspam@spam@MITVMA.MIT.EDU>








To:      PICLISTEraseMEspam@spam@MITVMA.MIT.EDU

cc:      (bcc: Andrew Kunz/TDI_NOTES)



Subject: Re: [OT] [EE] 24-bit A/D. Are We in the Twilite
         Zone Here?








Hi,

wrt. Andy Kunz's adding digital noise: I think that I know what is on.

He said that he has a very poor S/N at the input. I infer that he tried to
obtain a steady readout of the average RF level measured while receiving
modulated (AM ? - he does not say) rf signals. For this, he needed to
smooth the input somehow, to obtain something resembling RMS. By adding
'fast' noise I think that he faked oversampling, and then averaged the
result. This would be a median filter, done otherwise, imho. He also said,
that 'the result was surprisingly accurate' which means that he was
measuring the same signal also using other means, which means for RF are
either a specan or a rf milivolt/miliwattmeter. All three devices read out
RMS integrated over some time unless set up otherwise (i.e. peak or
instant power etc).

am I way off ?

Peter

2000\05\05@103327 by Robert A. LaBudde

flavicon
face
<x-flowed>I may be naive, but:

1. How do you generate a 24-bit voltage reference for a 24-bit ADC?

2. How do you know whether or not you have obtained 24-bits of accuracy?

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: RemoveMEralspamspamBeGonelcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causas scire"
================================================================

</x-flowed>

'8051 Programmer ? [OT] [EE]'
2000\05\06@002957 by Wagner Lipnharski

flavicon
face
Take a look at http:/whttp://www.ustr.net select 8051 files button, and get
ISPDOS.EXE, it is an executable DOS code (not Windows DOS), that allows
you program the 8k code flash memory of the AT89S8252 (8051) Atmel part
using only the PC Parallel port and 5 wires...

2000\05\06@045245 by Sebastian Garcia

flavicon
face
Hi Wagner!

Thanx! It's difficult to get the 8051's ISP parts in my country, so my next
question is if You can point me to a simple programmer for the more common
parallel parts. OK, I know that it won't be so simple as 5 wires but it
goes...

Thank You again,

S.-



-----Original Message-----
From: Wagner Lipnharski <spamBeGonewagnerKILLspamspam@spam@USTR.NET>
To: PICLISTspam_OUTspam@spam@MITVMA.MIT.EDU <spamBeGonePICLIST@spam@spamMITVMA.MIT.EDU>
Date: Saturday, May 06, 2000 1:29 AM
Subject: Re: 8051 Programmer ? [OT] [EE]


|Take a look at http:/whttp://www.ustr.net select 8051 files button, and get
|ISPDOS.EXE, it is an executable DOS code (not Windows DOS), that allows
|you program the 8k code flash memory of the AT89S8252 (8051) Atmel part
|using only the PC Parallel port and 5 wires...
|

'[OT] [EE] Need replacment for AMP-02 in SOIC-8 pac'
2000\05\08@025201 by William K. Borsum

flavicon
face
<x-flowed>Greetings:

I urgently need a replacement for the Analog Devices AMP-02 instrumentation
amplifier--but in a standard 8-pin SOIC package.

Key parameters are 200 KHz bandwidth through a gain of 500, and preferably 1000
+/- 15 volt power rails.
SOIC-8 package.

There are lots of IA chips out there--but I haven't been able to find one
in the right package with the wide BW.  So far I've struck out with Analog
Devices, Maxim, and Burr Brown.

ANY suggestions would be welcome.

Thanks
Kelly
William K. Borsum, P.E. -- OEM Dataloggers and Instrumentation Systems
<RemoveMEborsumEraseMEspamKILLspamdascor.com> & <http://www.dascor.com>San Diego, California, USA

</x-flowed>

'NTSC Video [OT][EE]'
2000\05\08@164906 by Sean Breheny

face picon face
Hi all,

Could someone point me to a good online reference on NTSC video?

Also, could someone please tell me if there is a way to determine which
field is odd and which is even? From the (poorly written) reference I am
currently looking at, it looks as if the vertical sync is the same for
both the odd and even fields so that when you assemble the frame, you
don't know which field belongs to which frame (and, therefore, you odn't
know which is odd and which is even).

Thanks,

Sean

2000\05\09@074226 by Andrew Kunz

flavicon
face
Sean,

I don't have a reference, but the two fields are very different.  There are many
chips out there which will provide A/B differentiation to you.  It can be done
with a PIC, but it's LOTS easier to let a chip do it for you.

Andy

2000\05\09@075319 by kayode.ayandokun

flavicon
face
> Hi all,
>
> Could someone point me to a good online reference on NTSC video?
>
Try any of the Elantec video IC data sheets, start with the EL4583 sync
separator.  I think you'll find that it gives a good explanation of the
basic waveform of the video signal with diagrams relating it to the
output of the chip.  http://www.elantec.com/pages/products_video.html

> Also, could someone please tell me if there is a way to determine which
> field is odd and which is even? From the (poorly written) reference I am
> currently looking at, it looks as if the vertical sync is the same for
> both the odd and even fields so that when you assemble the frame, you
> don't know which field belongs to which frame (and, therefore, you odn't
> know which is odd and which is even).

If you use a sync separator chip as above you have a digital output
indicating which field is which.  From the raw video waveform the
difference between fields can be worked out from the relationship
between the horizontal sync. pulses and the vertical sync. pulse during
the vertical blanking interval.  See the timing diagrams in the above
data sheet.

For a detailed description of a simple video digitizing circuit built
with discrete logic visit http://www.ucl.ac.uk/~ucapwas/video.html.
Not sure if there are low cost single chips for timing/digitisation

Kayode.
____________________________________________________________________
Put your next PIC project on TV!
http://www.blackboxcamera.com/Stv5730a/STV5730A.htm

2000\05\09@121736 by Lea

picon face
At 04:47 PM 5/8/00 -0400, you wrote:
>Could someone point me to a good online reference on NTSC video?

HI!, take a look at http://I.am/thekingofpic
there are a couple of links on that page with very nice video reference.
>
>Also, could someone please tell me if there is a way to determine which
>field is odd and which is even? From the (poorly written) reference I am
>currently looking at, it looks as if the vertical sync is the same for
>both the odd and even fields so that when you assemble the frame, you
>don't know which field belongs to which frame (and, therefore, you odn't
>know which is odd and which is even).

I'm at work now, I don't have the digital camera here but late at night I
can send you a image of how looks both fields on the Scope.
you will have to wait, sorry :-)

see you.
  Leandro J. Laporta (LU2AOQ)     mail: spamBeGonelu2aoqspam_OUTspamRemoveMEyahoo.com
wrk: Arg. Assoc. for Space Tech.   ham: TCP/IP high speed group HSG


__________________________________________________
Do You Yahoo!?
Talk to your friends online with Yahoo! Messenger.
http://im.yahoo.com

'CNC: G Codes decoding [OT] [EE]'
2000\05\09@215318 by Sebastian Garcia

flavicon
face
Hi all!

Can anyone point me to a CNC technical site where I can find explains in
detail of the use and decoding of G-Codes and M-Codes for CAM?.

(Sorry for the OT but I've been searching the net for it and found nothing
technical CNC)

Also a good book on this topic?

Thanks in advence,

S.-

2000\05\10@025449 by Stephan Kotze

picon face
Do a search for Stepster on the net. or a file called CNC981.zip. In it you
will find a document entiitled NCreadme.txt which will explain the codes

If you don't find it email me off list and I will forward it to you.

Stephan
{Original Message removed}

'[OT][EE] Audio Distribution - need answers, offlin'
2000\05\10@064342 by Hardware Engineering

picon face
I need to find some folks who are familiar with audio distribution and take
this offline to discuss.  This is not PA but music.

Basis of the problem is an outdoor setting and driving several speakers around
a hundred feet from the amplifier.  I need to find a good method of doing
this.

PLEASE...respond to either this email (read the list when I have time) or
prefer to .....ut_imagineerspamRemoveMEyahoo.com.  Lets not have a thread in the list
discussing it.

____________________________________________________________________
Get free email and a permanent address at http://www.netaddress.com/?N=1

'Anyone using Vutrax? [OT][EE]'
2000\05\11@133846 by jamesnewton

picon face
I've searched the archive and don't find mention of Vutrax from
http://www.vutrax.co.uk

Does anyone have experiences with this circuit/PCB CAD program?

I'm running out of patience with trying to understand Eagle and the current
projects are complex enough that the lack of a linked schematic in
ExpressPCB (which works great otherwise, and I don't care how lame that
makes me look) is becoming a problem.

---
James Newton jamesnewtonspam@spam@geocities.com 1-619-652-0593
http://techref.massmind.org
All the engineering secrets worth knowing

'G Codes decoding [OT] [EE]'
2000\05\11@193946 by Sebastian Garcia

flavicon
face
Thank You!

Best Regards,

S.-

-----Original Message-----
From: Stephan Kotze <EraseMEstephankRemoveMEspamSTOPspamIAFRICA.COM>
To: RemoveMEPICLISTKILLspamspamTakeThisOuTMITVMA.MIT.EDU <spamBeGonePICLISTspam@spam@MITVMA.MIT.EDU>
Date: Wednesday, May 10, 2000 3:55 AM
Subject: Re: G Codes decoding [OT] [EE]


|Do a search for Stepster on the net. or a file called CNC981.zip. In it you
|will find a document entiitled NCreadme.txt which will explain the codes
|
|If you don't find it email me off list and I will forward it to you.
|
|Stephan
|----- Original Message -----
|From: Sebastian Garcia <RemoveMEsgarciaspam_OUTspamTRON.FI.UBA.AR>
|To: <PICLISTspamspamMITVMA.MIT.EDU>
|Sent: Wednesday, May 10, 2000 3:48 AM
|Subject: CNC: G Codes decoding [OT] [EE]
|
|
|> Hi all!
|>
|> Can anyone point me to a CNC technical site where I can find explains in
|> detail of the use and decoding of G-Codes and M-Codes for CAM?.
|>
|> (Sorry for the OT but I've been searching the net for it and found
nothing
|> technical CNC)
|>
|> Also a good book on this topic?
|>
|> Thanks in advence,
|>
|> S.-
|

'8051 Programmer ? [OT] [EE]'
2000\05\12@110959 by Octavio Nogueira

flavicon
face
|Take a look at http:/whttp://www.ustr.net select 8051 files button, and get
|ISPDOS.EXE, it is an executable DOS code (not Windows DOS), that allows
|you program the 8k code flash memory of the AT89S8252 (8051) Atmel part
|using only the PC Parallel port and 5 wires...
|

Is this link ok?

Friendly Regards

Octavio Nogueira
===================================================
spam_OUTnogueiraspam_OUTspamspam_OUTpropic2.com                  ICQ# 19841898
ProPic tools - low cost PIC programmer and emulator
http://www.propic2.com
===================================================

----- Original Message -----
From: Sebastian Garcia <sgarciaspam_OUTspamTRON.FI.UBA.AR>
To: <RemoveMEPICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent: Saturday, May 06, 2000 5:44 AM
Subject: Re: 8051 Programmer ? [OT] [EE]


> Hi Wagner!
>
> Thanx! It's difficult to get the 8051's ISP parts in my country, so my
next
> question is if You can point me to a simple programmer for the more common
> parallel parts. OK, I know that it won't be so simple as 5 wires but it
> goes...
>
> Thank You again,
>
> S.-
>
>
>
> {Original Message removed}

'xilinx school project [OT][EE]'
2000\05\12@120733 by Arthur

flavicon
face
This is a School Project I found that is using xilinx chips for the controll
of lathe and pillar drilling marchines, Using eagle pcb tools,  look most
intresting
as anybody on the list used these devices?
details of chip and programmer from
http://xilinx.com
and the school project is
http://freeandeasy.sourceforge.net

best regards Art

'8051 Programmer ? [OT] [EE]'
2000\05\12@183952 by Sebastian Garcia

flavicon
face
Octavio,

It's http://www.ustr.net/ , the web page of Wagner.


Regards,

S.-

-----Original Message-----
From: Octavio Nogueira <nogueiraspamBeGonespam.....AJATO.COM.BR>
To: KILLspamPICLISTspam.....MITVMA.MIT.EDU <spam_OUTPICLISTspamKILLspamMITVMA.MIT.EDU>
Date: Friday, May 12, 2000 12:19 PM
Subject: Re: 8051 Programmer ? [OT] [EE]


||Take a look at http:/whttp://www.ustr.net select 8051 files button, and get
||ISPDOS.EXE, it is an executable DOS code (not Windows DOS), that allows
||you program the 8k code flash memory of the AT89S8252 (8051) Atmel part
||using only the PC Parallel port and 5 wires...
||
|
|Is this link ok?
|
|Friendly Regards
|
|Octavio Nogueira
|===================================================
|RemoveMEnogueiraRemoveMEspamEraseMEpropic2.com                  ICQ# 19841898
|ProPic tools - low cost PIC programmer and emulator
|http://www.propic2.com
|===================================================
|
|----- Original Message -----
|From: Sebastian Garcia <KILLspamsgarciaspamspamBeGoneTRON.FI.UBA.AR>
|To: <PICLISTspamspamMITVMA.MIT.EDU>
|Sent: Saturday, May 06, 2000 5:44 AM
|Subject: Re: 8051 Programmer ? [OT] [EE]
|
|
|> Hi Wagner!
|>
|> Thanx! It's difficult to get the 8051's ISP parts in my country, so my
|next
|> question is if You can point me to a simple programmer for the more
common
|> parallel parts. OK, I know that it won't be so simple as 5 wires but it
|> goes...
|>
|> Thank You again,
|>
|> S.-
|>
|>
|>
|> -----Original Message-----
|> From: Wagner Lipnharski <RemoveMEwagnerspamBeGonespamRemoveMEUSTR.NET>
|> To: KILLspamPICLISTspamBeGonespamMITVMA.MIT.EDU <@spam@PICLISTSTOPspamspam@spam@MITVMA.MIT.EDU>
|> Date: Saturday, May 06, 2000 1:29 AM
|> Subject: Re: 8051 Programmer ? [OT] [EE]
|>
|>
|> |Take a look at http:/whttp://www.ustr.net select 8051 files button, and get
|> |ISPDOS.EXE, it is an executable DOS code (not Windows DOS), that allows
|> |you program the 8k code flash memory of the AT89S8252 (8051) Atmel part
|> |using only the PC Parallel port and 5 wires...
|> |
|

'[EE][OT] STRIP-X (enamel wire)'
2000\05\16@044518 by Joe McCauley

picon face
As I indicated a soldering iron is how I am doing this at the moment but
with wire as fine as 0.032mm
you can very easily damage the wire. If you are making contacts on a
precisely wound and balanced 5K turn
balanced coil system you cannot afford to loose any wire from the end of the
winding never mind at the start
of the winding. A chemical stripper is the best way to go here IMHO.

Joe

{Original Message removed}

'[OT] [EE] Current is Flowing'
2000\05\16@101531 by Mark Peterson

flavicon
face
>From:    Gabriel Caffese <gabrielsdispamBeGonespamspamBeGoneIMPSAT1.COM.AR>
>Subject: How to know it there a current is flowing...
>

>Hello,
>
>        I need to know if a small current, that falls between 0.2ma and
3ma,
>flows over a pair of copper wires of printed circuit boards.
>        Those printed circuit boards cannot be touched, and I cannot
insert
>any standard measurement equipment, because there is no available space as
>to do that.
>        The only way (I think) , is to use something like a Hall effect
>transistor, wich can be hardly put (but can at last), below the printed
>circuit boards that are being inserted.
>        So, I would like to know if someone has ever done something like
>this before, and, if I am on the right way, and this can be done.
>
>            Hope to receive news from you !!!!

You could use a Hall effect, either open loop or closed loop.  In open
loop, the amplified output of a Hall element is directly used as the
measurement value.  Offset and drift are determined by the Hall element and
the amplifier.  These sensors have low price but also have low sensitivity.
For closed loop, the Hall voltage developed across the sensor, that is
placed in the gap of a magnetic core that surrounds one of your conductors,
is highly amplified and the amplifier's output current then flows through a
compensation coil wound on the same magnetic core.  It generates a magnetic
field that has the same amplitude but opposite direction as the field due
to current flow in the monitored conductor.  The result is that the
magnetic flux in the core is compensated to zero.  Closed loop sensors are
more sensitive and precise, but they also require more cost and effort to
implement.

Another option is the use of a magnetoresistive sensor.  These are devices
that have ferromagnetic materials deposited as thin films in narrow strips
while in a magnetic field.  The resistance of this material varies in
relation to the magnitude of a magnetic field they are placed in.  They are
usually used in a bridge arangement and offer good sensitivity.  Their
linearity is not very high so the same compensation principle used with the
closed loop Hall sensors should be used with these.

Mark P

'[OT] [EE] PC board transfer paper play'
2000\05\16@104655 by Mark Willis

flavicon
face
(Sorta funny one here <G>)

Found out what happens, yesterday, when you try to make a PCB by
printing on regular laser printer paper and ironing that on - I'd use
that for some big-trace boards (Heavy duty power supplies with 1/4"
traces etc., should work great!) - I will NOT recommend it, though, for
the 32-pin PLCC adapter I was making.  The paper sticks to the toner
rather thoroughly, does stick to the PCB well also.  I gave up and got
out the DynaArt paper after using acetone to clean up my little PCB
blank.

I'm always ready to try new things out, lets me problem solve - fun!
<G>  You do want to pull the plain paper off "flat" i.e. fold it over
180 degrees, then pull, after soaking for some time - seems to release
best that way.  Expect to rub off the rest of the paper fibers,
carefully, a bit at a time.  Probably, you could etch and the etchant
would eat in and only the toner would effectively resist - I didn't go
that far, maybe will next time.  The little adapter PC board I make (if
I didn't have 500 spare already!) would be a good testbed to try this
one out on, come to think of it.

(Got tired of trying to hand make little SOIC once-off's, toner does SO
much better so much easier than I can do offhand!)

Has anyone tried either spraying PVA (PolyVinyl Alchohol), or dextrin
solution, on their own paper to home-make an equivalent to the DynaArt
transfer paper?  It'd be quite convenient for me, to be able to make
quick once-offs more regularly (the DynaArt paper $3ish/sheet bill sure
adds up.  Less price per page would be nice - that thinking spawned the
"plain paper" try <G>)

I'm thinking you could roll or spray the PVA or Dextrin onto glass then
drop the paper onto that & clamp it (to keep it FLAT!), as one
possibility.  A little food coloring mixed into the PVA or Dextrin would
tell you which side to print onto.

Yes, I know, there are other "alternate print media" <G>  So little
time, so many mad science experiments <G>

 Mark

'[OT] [EE] Reply to "Is Current Flowing?"'
2000\05\16@110835 by Mark Peterson

flavicon
face
>From:    Gabriel Caffese <spamBeGonegabrielsdispamIMPSAT1.COM.AR>
>Subject: How to know if there a current is flowing...
>

>I need to know if a small current, that falls between 0.2ma and 3ma,
>flows over a pair of copper wires of printed circuit boards.
>Those printed circuit boards cannot be touched, and I cannot insert
>any standard measurement equipment, because there is no available space as
>to do that.
>The only way (I think) , is to use something like a Hall effect
>transistor, wich can be hardly put (but can at last), below the printed
>circuit boards that are being inserted.

You could use a Hall effect, either open loop or closed loop.  In open
loop, the amplified output of a Hall element is directly used as the
measurement value.  Offset and drift are determined by the Hall element and
the amplifier.  These sensors have low price but also have low sensitivity.
For closed loop, the Hall voltage developed across the sensor, that is
placed in the gap of a magnetic core that surrounds one of your conductors,
is highly amplified and the amplifier's output current then flows through a
compensation coil wound on the same magnetic core.  It generates a magnetic
field that has the same amplitude but opposite direction as the field due
to current flow in the monitored conductor.  The result is that the
magnetic flux in the core is compensated to zero.  Closed loop sensors are
more sensitive and precise, but they also require more cost and effort to
implement.

Another option is the use of a magnetoresistive sensor.  These are devices
that have ferromagnetic materials deposited as thin films in narrow strips
while in a magnetic field.  The resistance of this material varies in
relation to the magnitude of a magnetic field they are placed in.  They are
usually used in a bridge arangement and offer good sensitivity.  Their
linearity is not very high so the same compensation principle used with the
closed loop Hall sensors should be used with these.

Mark P

2000\05\16@113624 by Mark Peterson

flavicon
face
You could use a Hall effect, either open loop or closed loop.  In open
loop, the amplified output of a Hall element is directly used as the
measurement value.  Offset and drift are determined by the Hall element and
the amplifier.  These sensors have low price but also have low sensitivity.
For closed loop, the Hall voltage developed across the sensor, that is
placed in the gap of a magnetic core that surrounds one of your conductors,
is highly amplified and the amplifier's output current then flows through a
compensation coil wound on the same magnetic core.  It generates a magnetic
field that has the same amplitude but opposite direction as the field due
to current flow in the monitored conductor.  The result is that the
magnetic flux in the core is compensated to zero.  Closed loop sensors are
more sensitive and precise, but they also require more cost and effort to
implement.

Another option is the use of a magnetoresistive sensor.  These are devices
that have ferromagnetic materials deposited as thin films in narrow strips
while in a magnetic field.  The resistance of this material varies in
relation to the magnitude of a magnetic field they are placed in.  They are
usually used in a bridge arangement and offer good sensitivity.  Their
linearity is not very high so the same compensation principle used with the
closed loop Hall sensors should be used with these.

Mark P

'[OT] [EE] Current is Flowing'
2000\05\16@115723 by jamesnewton

face picon face
Mark, Thank you very much for replying to this post and adding the correct
tags in the subject line. Well Done! It is a great boost to the moral of
your hard working admins to know that at least some people are listing, care
about the list, and are willing to take a few moments to do what it best for
it.

---
James Newton (PICList Admin #3)
spam_OUTjamesnewtonSTOPspamspampiclist.com 1-619-652-0593
PIC/PICList FAQ: http://www.piclist.com or .org

{Original Message removed}

'[OT] [EE] PC board transfer paper play'
2000\05\16@120750 by Randy A.

picon face
Mark:

Try buying some laser or inkjet labels ( I use the 3.5 floppy labels), peel
off the labels and print the PC trace onto the shiny backing paper the labels
were on with you laser printer.  Then you can iron them onto the copper clad
board with a common household iron.  Of course make certain that your board
is very very clean and also put another piece of paper over the top of the
backing sheet to put your iron on.  Preheat the board with the iron for about
30 seconds to 1 minute before you actually iron on the transfer.  Then place
the trace printout on the board, put the blank paper sheet on the backing and
place the iron on it.  Keep the iron with moderate pressure on there and move
it around slowly for about 2 minutes.  You may have to experiment with the
heat settings on the iron to get the proper results as irons all differ
somewhat.  I would start with the lowest and go until I had the setting you
need.

Carefully peel off the label backing material and hopefully you will have
your resist trace intact and ready for etching.

You might want to check out Al Williams web site as he has the detailed
instructions for doing PCBs this way.

Regards and hope this helps,
Randy A.

2000\05\16@131403 by Mark Willis

flavicon
face
That's been on my Try list, just haven't gotten to it yet <G>  I've
wondered if you can re-use the backing paper repeatedly, or is it
one-use only?  I can get shipping labels and use those to generate shiny
paper, will probably try the Glossy Magazine heavy stock first though.

 Mark

Randy A. wrote:
{Quote hidden}

--
I re-ship for small US & overseas businesses, world-wide.
(For private individuals at cost; ask.)

2000\05\16@141306 by M. Adam Davis

flavicon
face
Many of the paper's properties are destroyed when heated and soaked...

-Adam

Mark Willis wrote:
{Quote hidden}

2000\05\16@143936 by Alice Campbell

flavicon
face
however, watercolorists wet paper repeatedly, and scrub at
it, even.  plain office paper is pretty pathetic, however
there are lots of paper types around, and im beginning to
think about kitchen waxed paper and shiny butcher paper,
stuck to thicker stock with a gluestick for a carrier through
the machine....
alice


{Quote hidden}

2000\05\16@153321 by Kris Wilk

flavicon
face
<x-flowed>A brief word of warning:

Laser printer fusers get very hot. The hot fuser can have all sorts of
interesting effects on various materials being fed against it. I would be
very leery about feeding some of the things I've heard suggested here and
elsewhere. Certainly anything waxy may have a tendency to gob melted goo
all over the insides of your printer if it can't take the heat. I remember
a guy telling me a story about someone who fed the wrong brand of
transparency through his laserjet and ended up with a mass of solid plastic
in the paper path...instant junker.

Of course some of the methods mentioned might work just dandy. It will
depend on the printer's fuser temperature a lot. Just because another guy
gets something to work doesn't mean it won't kill a different machine.

Kris

At 04:08 AM 5/16/00, you wrote:
>however, watercolorists wet paper repeatedly, and scrub at
>it, even.  plain office paper is pretty pathetic, however
>there are lots of paper types around, and im beginning to
>think about kitchen waxed paper and shiny butcher paper,
>stuck to thicker stock with a gluestick for a carrier through
>the machine....
>alice

</x-flowed>

2000\05\16@155820 by Arthur

flavicon
face
A neat solution to paper feed the relese paper through the printer is to
print onto paper stock, then cut-out a piece of relese paper the size of pcb
image and fix to paper with 3M magic tape along the leading edge of the
paper going into the printer {this tape is very thin and does not jam in the
printer}

Regards Art

{Original Message removed}

'[OT] [EE]No LED in Protel????'
2000\05\16@164412 by l.allen

picon face
>  Won't PROTEL allow you to make your own footprints?   If not,
>  I'd be finding another CAD program.
>
>                                         Regards,
>
>                                           Jim

Yes   you can make you're own footprints.

I find that not a problem, a couple of pads and a string, I
don't find too difficult BUT there are other much more
heinous features that really really really annoy me.

One is that every upgrade favours the Macro applications
and makes Micro (small) applications more and more
difficult. Early Protel was brilliant, fast, easy to use and
intuitive but then came OrCad compatibility and it all went
down hill from there IMHO.
An example.. Protel 98 PCB, on manual placement, will
not let you change pad size until AFTER you have placed
them... so no matter what, the default PAD is the only
one you can put down initially. This was not the case in
previous versions and is intensely annoying.. there are
more but I have said enough.
The main reason I stick with it now is my PCB
manufacturers can take a file from Protel and there is
never a problem with that file becoming a PCB.
The same reason I am forced to use ( and upgrade
endlessly) to ......... Microsoft   ..compatibility.

_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

'[EE] Labels'
2000\05\16@195058 by William K. Borsum

flavicon
face
<x-flowed>Hi All:

Revisiting the subject of making you own professional looking labels.....

I have located a 10-mil thick  polycarbonate film that seems to be working
very well with ink-jet printers.
The printing is done on the back, using a mirror image.  The film is then
coated with the desired background color (regular Krylon or other spray
paint), and a double sided tape or spray adhesive is applied.  Once applied
to the panel, the ink layer is fully protected by the Polycarbonate film.

The resulting label is as good as your layout software will allow (Word,
Protel, Publisher, etc), and resolution of your ink-jet printer.  BUT it is
subject to moisture (ink-jet ink is water based) wicking in around the
edges, and fading if left in full sun for a year.  There is a coating
available that I am exploring that may solve the moisture problem.

The 10-mill film is rather rigid, can cover holes, be "bubbled" to form
membrane switches, left clear for LED's to show through, etc.  This is
basically the same stuff the "pro's" use.

In my case, I even lay out the hole centers and cutouts on the label as
guides for drilling, punching, or routing after the label is applied to the
panel.

Here's the problem--I've got to buy the stuff in LARGE rolls. Something
like 3 feet by 120 feet.

THE QUESTION:  is anyone out there interested in buying kits if I get a
roll, and cut it down to 11x17 or 8.5x11 inch size, and include the really
good 3-M adhesive normally used with this type of film?  Don't have an
accurate cost yet, but guessing about $2 per letter size sheet, and maybe
$4-10 for the adhesive depending on the type.  Target price for a kit would
be maybe $25-$50..

If you are interested, please contact me OFF THE LIST, and let me know your
thoughts--sizes, quantities, etc.

Kelly
William K. Borsum, P.E. -- OEM Dataloggers and Instrumentation Systems
<RemoveMEborsumspamspamdascor.com> & <http://www.dascor.com>San Diego, California, USA

</x-flowed>

'[OT] [EE] PC board transfer paper play'
2000\05\16@223601 by Randy A.

picon face
Nope, you can't use the backing but once.  I tried and it just doesn't seem
to work very well.

Randy A.

2000\05\16@224011 by Randy A.

picon face
Hey, the waxed paper might work.  Although I am not sure about what the wax
will do to the copper board as far as the ethant is concerned.

Randy

2000\05\16@224017 by Randy A.

picon face
OOPS, Kris you are right, forgot about that 180 plus temp on the fuser,  wax
paper is probably out then.

Randy

2000\05\17@012709 by William Chops Westfield

face picon face
I believe that the backing of laser-compatible labels are coated with
silicone of some kind.  Teflon might work as well - perhaps some of those
teflon-coated fiberglass "cloths" used for release coatings in composite
constrution.  Hmm...

I think some of the backings for plastic "labels" are also silicone based,
and sometimes much thicker and stronger than the paper-label backing (due to
tougher adhesives and thicker plastic as well.)

BillW

'[EE] Embedded Java'
2000\05\17@092232 by Jon Hylands

flavicon
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On Wed, 17 May 2000 07:42:40 -0500, "Clark, John" <TakeThisOuTJohnCspamspamRemoveMEININ.COM> wrote:

> I am looking for an inexpensive microcontroller which I can program in Java.
> I have no need for advanced Java features like multithreading or garbage
> collection -- a compiler which would turn Java into assembler would be fine.
> I looked at the Scenix VM, but it has some $25,000 licensing fee.   I did
> see that IBM has a product for embedded Java:

Check out http://www.rtjcom.com

He has a RTJ that will run on a 68HC11...

Note that his version does include multi-tasking, garbage collection, and
exception handling.

Later,
Jon

--------------------------------------------------------------
  Jon Hylands      KILLspamJonspamspamspam_OUThuv.com      http://www.huv.com/jon

 Project: Micro Seeker (Micro Autonomous Underwater Vehicle)
          http://www.huv.com

'Embedded Java [OT][EE]'
2000\05\17@093945 by Bennett, Matt

flavicon
face
www.ibutton.com/TINI/index.html

Embedded Java, Ethernet, TCP/IP, $50 (USD) for a board with 512K NVSRAM.
Built onto a board with a SIMM form factor.  Made by Dallas Semiconductor.

Matt Bennett

{Original Message removed}

'[OT] [EE] PC board transfer paper play'
2000\05\17@105055 by Brian Hopkins

flavicon
face
I think this quest for quick, afforable protyping, on copper-clad
fiberglass, has dogged many of us.
Midnight engineering holy grail.

Bob Blick's  excellent pages - COM84 project mentioned 'a page from TIME
magazine'.
www.bobblick.com/bob/projects/f84pgm/index.html
(Medical offices providing obvious source, plus this has a 'green'
environmental feel to it...reuse, recycle)
I had to try it. It seems to have possibilties.  . The heat level was too
high on the iron, and the iron was reclaimed by it's owner, back to a boring
life working on quilting projects. I'll have to buy my own. (any
recommendations?)
Hopefully Mr Blick can lend a hand here, and expand on his experences...

One thing I have found is to push the limit of 'darkness' on my printer
setup, to lay down as much toner as possible.

Also, for those mad scientist types, what about the qualities of different
toners?. Specifically, the amounts and types of plastic granules? Is there a
better toner we could be using to refill our own cartridges?
Any research results?

Brian

2000\05\17@130716 by Donald Brown

picon face
Where is Al Williams web site.  http ??


--- "Randy A." <Cnc002RemoveMEspamAOL.COM> wrote:
{Quote hidden}

__________________________________________________
Do You Yahoo!?
Send instant messages & get email alerts with Yahoo! Messenger.
http://im.yahoo.com/

2000\05\17@201441 by Brian Kraut

picon face
I would bery strongly advise not putting wax paper through your laser printer.
I don't think that a coating of melted wax on your fusion rollers would be a
very good idea, not to mention that you couldn't iron it on without just making
a waxy mess anyway.

"Randy A." wrote:

> Hey, the waxed paper might work.  Although I am not sure about what the wax
> will do to the copper board as far as the ethant is concerned.
>
> Randy

'[EE] Interfacing PIC to automotive electrics?'
2000\05\17@210908 by Gennette, Bruce

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Hi all,

Probably been explained before, but how do I interface a 5V PIC to the
signals coming from 12V car (and 24V truck) devices like temperature and oil
pressure sensor/senders?

I suspect that cars can use CMOS comparitors set against a trim pot (with
zeners to divert any spikes), but how about truck (or boat) engines using
24V?

Could I use voltage dividers to bring the signals down to the 0-5V range and
directly connect to a PIC or TTL gates?

For this first project I'm just looking at the alarm state ( !Ok ), but
later I may want to log all parameters so that a progressive failure can be
spotted (eg cooling water temp hotter each day indicates a growing blockage
in the system or excessively worn pump).

If there is an existing FAQ could someone point me to it please?

Thanxs in advance,
Bye.

'[EE] Interfacing PIC to automotive electric's?'
2000\05\17@220437 by Plunkett, Dennis

flavicon
face
18/5/2000


Can of worms can of worms!
There is the simple way, then there is the correct way.
Just of interest the relevant specifications are:-

CISPIR 25 1995-11
ISO/TR 10605 1994(e)
Japanese blue book
ISO 11452 1995(e)
MIL STD 461D
ISO 7637 (Gives the impulse tests)
SAE J1112-13 1995
SAE J1113-42 1994

OK!
So for protection you can use a normal resistive divider and then pass this
into a ESD device like a California micro P002 etc.

Your main problems are susceptibility, we now are testing with values of up
to (Get this one people if you think your world is noisy! 200V/meter at
frequencies up to 0.5MHz and 40V/meter amplitude modulated by 80% up to
10MHz) Failure rates are dependant on the module requirements etc.

Dennis





> {Original Message removed}

'[EE] Interfacing to automotive (now EMI)'
2000\05\17@222323 by Chris Eddy

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Krikey, Dennis, I feel more and more behind as the standards get more and more
complicated.  I do not aspire to own a full EMC/EMI test setup at this point,
but I would like to design to pass, and intelligently.  Can you suggest:

A    How to get the standars that you referenced below without spending 6
figures?

B    Some truly comprehensive texts that direct one to practical application

I got that EMI test compliance trade magazine for a while, bot boy do they bury
the answers deep.

Feeling an emptiness inside,
Chris Eddy

"Plunkett, Dennis" wrote:

> CISPIR 25 1995-11
> ISO/TR 10605 1994(e)
> Japanese blue book
> ISO 11452 1995(e)
> MIL STD 461D
> ISO 7637 (Gives the impulse tests)
> SAE J1112-13 1995
> SAE J1113-42 1994
>

2000\05\17@230323 by Plunkett, Dennis

flavicon
face
18/5/2000

You can attempt to get the requirements from the vehicle manufacturer, as
often they have a cut doen version that includes the testing, but alas that
can often hide you from the intention of the original spec.

Best to to a web search and see what occurs, as you now have a list of what
is required.

There is no one practical application as the tests depend on the
clasification of the device and where it is to be located (Sigh)

Dennis






> {Original Message removed}

'[EE] Interfacing PIC to automotive electric's?'
2000\05\17@231003 by rad0

picon face
test
----- Original Message -----
From: "Plunkett, Dennis" <EraseMEdplunkettSTOPspamspamRemoveMEAIRINTER.COM.AU>
To: <spam_OUTPICLISTRemoveMEspamEraseMEMITVMA.MIT.EDU>
Sent: Wednesday, May 17, 2000 8:59 PM
Subject: Re: [EE] Interfacing PIC to automotive electric's?


{Quote hidden}

this
> into a ESD device like a California micro P002 etc.
>
> Your main problems are susceptibility, we now are testing with values of
up
> to (Get this one people if you think your world is noisy! 200V/meter at
> frequencies up to 0.5MHz and 40V/meter amplitude modulated by 80% up to
> 10MHz) Failure rates are dependant on the module requirements etc.
>
> Dennis
>
>
>
>
>
> > {Original Message removed}

'little [PIC] more [EE]5v PIC <> 3v3 logic'
2000\05\18@021652 by Vasile Surducan

flavicon
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On 18 May 00, at 15:22, David Duffy wrote:

{Quote hidden}

 It's the best ideea, I don't know how I forgot ... PIC will see as
high level anything up to ~1,8V...2V .
And a CMOS have thresolds at 1/3 and 2/3 from VDD so 2/3 from
5V is 3.3V that's the reason why CMOS are unhappy when is
supplied at 5V and interfaced with a signal coming from a 3.3V
circuit... and not because of schmitt trigger inputs...
But a good (standard) CMOS chip will work either at 3V (with
frequency limitation ) so no problem...
Vasile
****************************************
Surducan Vasile, engineer
email:EraseMEvasileRemoveMEspaml30.itim-cj.ro
URL:http://www.geocities.com/vsurducan
****************************************

'[EE] Interfacing PIC to automotive electrics?'
2000\05\19@021208 by Damon Hopkins

flavicon
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"Gennette, Bruce" wrote:
{Quote hidden}

There's an article about the network systems in cars in the current
issue of Circuit Cellar.. If you can't find it let me know I can look up
what the documents are you need. It basically tells you about the 2
major different kinds of car networks and what SAE manuals to get w/ all
the details.  I forget which issue (MAY perhaps april) but the cover is
mostly black :)

Let me know if you can't get ahold of it and I'll throw you some
pointers from the text..

                       Damon Hopkins

2000\05\19@023747 by Plunkett, Dennis

flavicon
face
K-line?
CAN?
XDE?
JDOT?
DIS 14230?

Is a few off the top of my head, Which two is it?

Dennis


> {Original Message removed}

'Time Stamping [EE]'
2000\05\20@004504 by Robert Rolf

picon face
Andy, to give you a good answer we need to know a bit more about
what kind of data rates you're using and what you define as 'accurate
time stamp'. All accuracy is relative. For Radio Astronomy, sub
nanosecond
is required if you're running a wide baseline interferometer.  For river
levels, minutes is sufficient.

GPS 1PPS will get you to +/- 30 nSec or so short term. 1E-10 to -12 with
a long term average and a disciplined clock. A tweaked and compensated
Dallas clock, a few seconds a month. A fine tuned PIC about the same.
Reference time is also available on GOES satellites (485Mhz or so).


What do you actually need? Absolute time, or relative? Battery backed
up, or can you survive a power outage and several minute recovery?
If you lock your sampling to an external clock you don't really need to
time stamp your samples. You just need to store the time stamp of the
first (or last) sample, and then compute the time based on sample
number.
Saves one heck of a lot of memory.

Ramana wrote:
{Quote hidden}

> {Original Message removed}

'[OT][EE] Phase locking DRO's'
2000\05\20@011942 by Robert Rolf

picon face
Given the diverse group on this list, perhaps someone can point
me in the right direction to solve this small problem: How to
Phase lock the cheap DROs (dielectric resonant oscillator) used in
consumer LNBs (C and Ku band) so that one can do interferometry?

Commercial PLL LNB's are way out of our price ranges ($1500 vs $50
for non-PLL) and the cheap versions have MUCH better noise figures.
I'm hoping that there is some simple way to control the on board
DRO so that a stable (and phase matched) LO can be achieved.
I've considered piezo electric (too slow). Varactors in proximity
to the cavity (doesn't seem to work but then I don't really know what
I'm doing). And plain old, change the VCC (again not fast enough).

Any suggestions on how one does a phase comparison at Ghz frequencies
(5150MHz) to a 100Mhz reference and then control a DRO would be
appreciated. I've been exploring a PIN diode sampler, but don't
seem to have the right configuration.
I have access to some decent tools, but they just don't
teach this kind of plumbing around here.

The other gotcha is how to ship a 1Ghz or so signal 300 meters (or 3 km)
without incurring huge losses (or outrageous cabling costs).
I assume that the same hardware that the cable people use for their
HFC plants would work. Know anyone with a couple of spare fiber
convertors
they'd like to donate to the cause <G>?


Some background:
With the large number of big dishes (BUDs) being dumped in
favor of the smaller DTH (LSDs), we thought it was a real waste to see
them hitting the dumpster, so we have been taking the great unwanted up
to the roof of our physics building to bootstrap an amateur radio
astronomy observatory. The physical construction is going well, but
it now falls upon me to come with with a decent RF section so that
we can doing meaningful science. This means using interferometry to get
sufficient sensitivity and resolution. (Widely separated dishes can
behave like a single big dish with suitable signal processing. You just
don't get the sensitivity (or the pointing headaches) of a single
large dish). Computers are cheap. Sound cards are cheap (and so are
3D video cards. Subvert the DSP and you've got one heck of a
correlator).

It is trivially easy to build a total power receiver (TPR) from surplus
C band hardware. Any of you who've experienced a sun-out (twice a year
the
sun passes behind the geosynchronous satellite and drowns out their
signals) have already done radio astronomy. It is much more difficult
to do interferometry since you need to either mix the signals from
two widely separated dishes at frequency (and the old LNA's had terrible
noise figures compared to today's LNBs), or have phase matched down
conversion and then mix the signal to get a correlation (and thereby
pull your extraterrestrial signal out of the noise). PLL LNB's are
just too expensive for an amateur group to afford, so I'm hoping to
be able to hack some cheap LNBs to do the job and get us started.

Thank you in advance for your time and suggestions.

spamRobert.Rolf.....spamspamUAlberta.ca

2000\05\20@100326 by Alan B Pearce

face picon face
>or have phase matched down
>conversion and then mix the signal to get a correlation (and thereby
>pull your extraterrestrial signal out of the noise). PLL LNB's are
>just too expensive for an amateur group to afford, so I'm hoping to
>be able to hack some cheap LNBs to do the job and get us started.

Just a suggestion - I have no experience with doing this - but have a look at
the chips sets used in GPS receivers, especially the correlator control chips
that have up to 12 correlators in them to lock onto the satellites. The two
chipsets I looked at are normally supplied with no code in the micro contained
in the correlator chip. If you get real friendly with a rep, they may donate you
a sample chip.

'Embedded Java [OT][EE]'
2000\05\20@130331 by Dan Michaels

flavicon
face
John Clark wrote:
>
>I am looking for an inexpensive microcontroller which I can program in Java.
>I have no need for advanced Java features like multithreading or garbage
>collection -- a compiler which would turn Java into assembler would be fine.
>I looked at the Scenix VM, but it has some $25,000 licensing fee.   I did
>see that IBM has a product for embedded Java:
....

Try ST22:  http://www.st.com/stonline/prodpres/smarcard/sc_idx.htm

Sun may have finally realized their javavaporchip into silicon after
2-3 years of hyping - might check there too.

I also have a bunch of links to Java [inc real-time J] on my site,
and you could try mining those:

http://www.sni.net/~oricom/emerge2.htm

best regards,
- Dan Michaels
Oricom Technologies
===================

'[EE] Non interacting zero and span. how?'
2000\05\21@002347 by Chris Eddy

flavicon
face
I have a question that is just burning me up.  And when I try to solve
it I get a mental block.

To simplify the problem, say I have an op amp circuit with an input
signal of 0-5VDC and a desired output of 1-5VDC.  I have a zero and a
span pot.  Normally, I build this circuit with the zero pot and the
signal in question summed with two resistors into the + pin of the amp.
Then wrap the output back to the negative pin with a pot for the span.

The big complaint form customers is that the zero and the span interact
a lot.  My quest is to change the circuit so that the zero pot
accurately sets the 1V level at 0V in, and then adjust the span pot for
5V out at 5V in.

By the way, the application is converting to 4-20mA.  Any output where
the ratio of low to high is 1:5 is acceptable.  It does not have to be
1V and 5V.

The application in mind has split rails, but it would be nice to have a
single supply solution for those other jobs too.  Any grand ideas come
to mind?

Chris Eddy
Pioneer Microsystems, Inc.

'[EE]: RC oscillator'
2000\05\21@004213 by goflo

flavicon
face
Not to argue with my friend Russell, but I'm not clear on what mix of
acceleration & vibration is being discussed - Surprising how much g
many devices will tolerate - For a period. The lethal AAA proximity
fuses fielded in the last year of WW2 were vacuum-tube technology...
A vibration-rich environment is a somewhat different animal. Metal
fatigue becomes a more significant factor, for instance. This kind of
thing is exhaustively investigated by the military services - What's in
the public domain I don't know.

regards, Jack

Russell McMahon wrote:
{Quote hidden}

'[EE] Non interacting zero and span. how?'
2000\05\21@011400 by Robert A. LaBudde

flavicon
face
<x-flowed>At 07:22 PM 5/20/00 -0400, Chris wrote:
>To simplify the problem, say I have an op amp circuit with an input
>signal of 0-5VDC and a desired output of 1-5VDC.  I have a zero and a
>span pot.  Normally, I build this circuit with the zero pot and the
>signal in question summed with two resistors into the + pin of the amp.
>Then wrap the output back to the negative pin with a pot for the span.
>
>The big complaint form customers is that the zero and the span interact
>a lot.  My quest is to change the circuit so that the zero pot
>accurately sets the 1V level at 0V in, and then adjust the span pot for
>5V out at 5V in.
>
>By the way, the application is converting to 4-20mA.  Any output where
>the ratio of low to high is 1:5 is acceptable.  It does not have to be
>1V and 5V.
>
>The application in mind has split rails, but it would be nice to have a
>single supply solution for those other jobs too.  Any grand ideas come
>to mind?

1. What is your current circuit?

2. What type of op-amp are you using?

3. Is an inverting configuration acceptable?

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: ralspam_OUTspam@spam@lcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causas scire"
================================================================

</x-flowed>

'[OT][EE] Phase locking DRO's'
2000\05\21@023202 by Robert Rolf

picon face
Alan B Pearce wrote:
>
> >or have phase matched down
> >conversion and then mix the signal to get a correlation (and thereby
> >pull your extraterrestrial signal out of the noise). PLL LNB's are
> >just too expensive for an amateur group to afford, so I'm hoping to
> >be able to hack some cheap LNBs to do the job and get us started.
>
> Just a suggestion - I have no experience with doing this - but have a look at
> the chips sets used in GPS receivers, especially the correlator control chips
> that have up to 12 correlators in them to lock onto the satellites. The two
> chipsets I looked at are normally supplied with no code in the micro contained
> in the correlator chip. If you get real friendly with a rep, they may donate you
> a sample chip.

Unfortunately these chipsets are very application specific.
Grossly simplified, they
look for a specific set of spread spectrum digital 'chips' {the pseudo
random spreading sequence unique to each satellite) at a very specific
rate. When they find a matching 'chip' they synchronize and
then provide a 50Hz recovered data frame rate which is subsequently
processed into pseudorange and ultimately location.

The Philips chipsets ARE available with microcode, for a price,
but the signals that are being extracted are so different from what
we look at that this approach would not work. Thanks for the suggestion
though.

Radio astronomy 'correlators' compare the signals from multiple
dishes and provide an output that is higher if the signal is correlated,
and lower is it is not (just random). In it's simplest form a
correlator is just an RF multiplier. Noise * noise= Noise, average
value=0. Signal * Signal = Signal ^2, with some average value.
[ever wonder why they're called 'square law' detectors?]

With noise+signal, the noise averages out to zero, but the -correlated-
noise (i.e. the same signal seen by two different dishes) is non zero.
This is what allows us (and NASA) to see a signal that is buried in
noise. In order for the multiplication to produce a result, the phase
relationship of the two signals must match, so the LO MUST be phase
locked (or you have to do the multiplication at frequency, and at 4Ghz
that's a bit difficult (not to mention the losses in bringing the two
signals together at a central correlator).

This description is a gross simplification of the process since one has
to compensate for many other phase shifts, but it all starts with a
phase locked LO in the downconvertor.

So? How do I phase lock a DRO? Pumping 5150Mhz around to the widely
separated dished just doesn't seem to be a viable alternative.

Robert.Rolf-at-ualberta.ca

'[EE] Non interacting zero and span. how?'
2000\05\21@071201 by paulb

flavicon
face
Chris Eddy wrote:

> Normally, I build this circuit with the zero pot and the signal in
> question summed with two resistors into the + pin of the amp.
> Then wrap the output back to the negative pin with a pot for the span.

> The big complaint form customers is that the zero and the span
> interact a lot.  My quest is to change the circuit so that the zero
> pot accurately sets the 1V level at 0V in, and then adjust the span
> pot for 5V out at 5V in.

 Unfortunately, it works the other way about.  Assuming the zero bias
potentiometer has a low impedance, the two controls do not interact much
at all.

 Your problem is that you are *not* zeroing it in the first place, but
setting an offset.  The offset of course, represents the real offset
multiplied by the scale (span) figure; of course it depends on both.

 The procedure you want is in three steps.  Set the zero control for
*zero* output with zero input.  Apply a 5V input and set the scale pot
for 4V output.  Set the input back to zero, and adjust zero bias for the
desired 1V output.
--
 Cheers,
       Paul B.

2000\05\21@074146 by Spehro Pefhany

picon face
At 07:22 PM 5/20/00 -0400, you wrote:
>I have a question that is just burning me up.  And when I try to solve
>it I get a mental block.
>
>To simplify the problem, say I have an op amp circuit with an input
>signal of 0-5VDC and a desired output of 1-5VDC.  I have a zero and a
>span pot.  Normally, I build this circuit with the zero pot and the
>signal in question summed with two resistors into the + pin of the amp.
>Then wrap the output back to the negative pin with a pot for the span.

Try a pot connected as a rheostat in *series* with the signal (summed
to the non-inverting input) and adjust the 1V level by summing to the
inverting input (fixed feedback resistor).
You'll need a -ve reference for this to work.

If you want to use a +ve reference it might be easier to buffer the
zero adjust voltage with an additional unity gain op-amp and use your
original circuit, but with the span adjust pot again in series with the
signal to the non-inverting input.

Best regards,

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Spehro Pefhany --"it's the network..."            "The Journey is the reward"
.....speffspamspam.....interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

'Embedded Java [OT][EE]'
2000\05\21@094828 by Clark, John

flavicon
face
>>Try ST22:  http://www.st.com/stonline/prodpres/smarcard/sc_idx.htm

Impressive.  I am familiar with the Dallas offerings (in response to the
other post on this subject), but until a single chip offering for under $5
is available, I don't think the "Java Everywhere" thing Sun sees will ever
materialize.  I am pleased to see that ST has developed hardware that will
natively execute byte code.  Do you know if they have any offerings in SOIC
or DIP packages?  The scan I just took of the website only revealed
offerings of naked chips and wafers.


John Clark
Indianapolis, IN


{Original Message removed}

'Driving a H-bridge with PWM[EE].'
2000\05\21@170502 by l.allen

picon face
Quentin Wrote...
> Hi
> I want to control the speed of a motor (24V,10A) with one PWM with
> direction and brake on a 16c87x.

This is one of those topics where the possibilities are
numerous but none are perfect IMHO.

There are nice Motor Drive IC packages that are the
easiest to use but I have found (at least in New Zealand)
are expensive, hard to get and/or are not available reliably.

I favour using mosfets in a bridge arrangement, either
mixed Nchannel and Pchannel or all Nchannel with raised
gate drives (high side driving) on the upper devices.

After numerous cost/ benefit, reliability and noise
immunity experiences my favoured system is now 4
Nchannel devices (much cheaper) forming the bridge
driven via a quad optocoupler. The collectors of the
optocoupler transistors connecting to a suitable drive
voltage (the only real snag I think), eg at 24 volts the
upper mosfets need typ 35 volts (29 volts if Logic level)
and of course the emitters of said optocouplers
connecting to the mosfet gates.

There are a number of ways of generating the gate bias
voltage but the easiest (if you are using a mains supply
via transformer/s) is to use a small transformer (or
unused winding) to generate say 12 volts and float that
supply, connecting the 0volt to the motor +ve supply, the
bias (for the upper mosfets) will always be 12 volts above
the motor voltage).

This will still need external glue logic in youre case but
this system is very reliable.

BTW I am developing a system at this very moment
using this arrangement driving a 24 volt 2.5 amp motor
but I am using both PWM outputs of a 16F877, one for
each direction.



_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

'Embedded Java [OT][EE]'
2000\05\21@171747 by Dan Michaels

flavicon
face
John Clark wrote:
>>>Try ST22:  http://www.st.com/stonline/prodpres/smarcard/sc_idx.htm
>
>Impressive.  I am familiar with the Dallas offerings (in response to the
>other post on this subject), but until a single chip offering for under $5
>is available, I don't think the "Java Everywhere" thing Sun sees will ever
>materialize.  I am pleased to see that ST has developed hardware that will
>natively execute byte code.  Do you know if they have any offerings in SOIC
>or DIP packages?  The scan I just took of the website only revealed
>offerings of naked chips and wafers.
>

Hi John,

I have no personal knowledge regarding this technology, just a few
links, which you can mine for your own purposes. However, some
poking around uncovered the general area of Javacards, which does
appear to have a lot of action:

http://java.sun.com/products/javacard/

I also have some other links to Javacards and smart cards on my site:

http://www.sni.net/~oricom/emerge3.htm

best regards,
- Dan Michaels
Oricom Technologies
===================

2000\05\22@121435 by Dan Michaels

flavicon
face
Also, ran across the following:

"Now Any Chip Can Be A Java Chip":
http://www.zdnet.com/sr/stories/news/0,4538,2460088,00.html

Jstar:
http://www.jeditech.com/

best regards,
- Dan Michaels
Oricom Technologies
===================

'[OT][EE] Phase locking DRO's'
2000\05\22@164937 by Peter L. Peres

picon face
Hi,

wrt locking DROs, I know that by tampering with the bias of the oscillator
transistor it is possible to pull the frequency a little bit (a few MHz
maximum at 10 GHz). Assuming that you can select from a number of DRO's,
find two that have the exact same (or near enough) frequency and try to
use them like this. The simplest form of tampering consists in changing
the supply voltage. The less simple one involves changes in the bias
circuit of the oscillator, but for the latter you need the schematics and
instruments. I do not know about the phase noise characteristics of
the DROs but I suspect that they are not very good. They should be
less good than a multiplier chain's followed by a DRO filter. Just an
opinion.

hope this helps,

       Peter

'[OT] [EE] PC board transfer paper play'
2000\05\22@204718 by marquis DeSade

picon face
hello all,
a trick i learned was to use 60lb paper in a laser
printer, the toner has plastic in it, and heavy bond
ie. 60-120lb paper has clay in it, so you iron it to
the black PCB and then soak in water, the clay and
toner stick leaving your artwork, and the rest falss
off...
cheers, desade


--- Brian Kraut <engaltKILLspamspamEraseMEEARTHLINK.NET> wrote:
{Quote hidden}

__________________________________________________
Do You Yahoo!?
Send instant messages & get email alerts with Yahoo! Messenger.
http://im.yahoo.com/

'[OT][EE] Phase locking DRO's'
2000\05\22@223250 by David Bengtson

picon face
Well, you have a somewhat complex problem on your hand. You will need
to end up building a Phase locked loop from the cheap DRO's that you
have. You will also  need to come up with a very stable reference
oscillator. Here is a rough ASCII Diagram (Fixed Pitch Font, Please)

 Ref--------Divider-------Phase-------Loop------DRO---------Stable RF
 Osc.                     Detector    Filter         |
                            |                        |
                            |                        |
                            |--- Divider-------------|

This is the canonical block diagram of a Phase Locked loop. You have
the Section marked DRO, and you need to design a build the rest of it.
Once you do that, you will be able to use this as a stable RF source
for doing Radio Astronomy and Radio Interferometry. I have seen
several web sites that talk about amateur radio astronomy, and a good
web search will turn up several, including ones that talk about
interferometry. I think that what you want to search for is Project
Bambi. (I don't name them).

GPS correletors are not the thing that you are looking for, although
you could use a GPS receiver to help with the reference oscillator.
The Accuracy of the reference oscillator determines the accuracy of
the entire system.

I would start with building one dish and then extending it to another
one.

This sounds like a fun project.


Dave Bengtson

On Sun, 21 May 2000 00:30:07 -0600, in  you wrote:

{Quote hidden}

'[OT] [EE] PC board transfer paper play'
2000\05\22@224254 by Spehro Pefhany

picon face
At 05:47 PM 5/22/00 -0700, you wrote:
>hello all,
> a trick i learned was to use 60lb paper in a laser
>printer, the toner has plastic in it, and heavy bond
>ie. 60-120lb paper has clay in it, so you iron it to
>the black PCB and then soak in water, the clay and
>toner stick leaving your artwork, and the rest falss
>off...
>cheers, desade

Coated paper has a clay layer (that's the paper that's
used to make "glossy" magazines).

It should be available in letter size from paper
distributors that cater to small printing companies (the
kind that are running ancient Multiliths and similar
sheet fed offset presses).

Such paper is often heavier than regular bond, but you
can buy thin coated paper as well.

It will be very cheap from such a source.

Best regards,

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Spehro Pefhany --"it's the network..."            "The Journey is the reward"
EraseMEspeff@spam@spam@spam@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

'[EE] Adjusting voltage output of a temperature sen'
2000\05\23@002310 by Dean Biddle

flavicon
picon face
Hi,

Are there alternative(s) to an operational amplifier (supplied by +ve and
-ve) to adjust the voltage output of an LM335 temperature sensor from
approx. 2.5 to 3.5 volts to span the 0 to 5 volt range for a P16F87x A/D
converter?  My application needs to consume minimal current and preferably
use only one battery.  Can another option for the configuration of the A/D
system be used other than limiting Vref+ to approx. 3.5 volts?

I assume this is common, so please simply refer me to a relevant past
PICLIST thread if I failed to match the thread in my "pre-post" search.

'[EE] Ethernet Chips'
2000\05\23@002608 by Damon Hopkins

flavicon
face
anyone have some info on where I might find a CHEAP ethernet transceiver
I found plenty of ways to hook up a microcontroller to a PC via PPP
but I want to plug straight into a hub.

                       Thanks,
                               Damon

'[EE] Adjusting voltage output of a temperature sen'
2000\05\23@002919 by Damon Hopkins

flavicon
face
Dean Biddle wrote:
>
> Hi,
>
> Are there alternative(s) to an operational amplifier (supplied by +ve and
> -ve) to adjust the voltage output of an LM335 temperature sensor from
> approx. 2.5 to 3.5 volts to span the 0 to 5 volt range for a P16F87x A/D
> converter?  My application needs to consume minimal current and preferably
> use only one battery.  Can another option for the configuration of the A/D
> system be used other than limiting Vref+ to approx. 3.5 volts?
>
> I assume this is common, so please simply refer me to a relevant past
> PICLIST thread if I failed to match the thread in my "pre-post" search.

Excellent question.. I await the answer because right now I'm using an
OP AMP to do it... I hope there is..

               Damon Hopkins

'[EE] Ethernet Chips'
2000\05\23@005140 by Todd Peterson

flavicon
face
> anyone have some info on where I might find a CHEAP ethernet
> transceiver

Damon,

Have a look at http://www.embeddedethernet.com for a cost-effective solution.  I'm
anxious to hear from anyone who has actually used this schematic; I'd
suspect that those who have played with ethernet and a micro have connected
to an ISA card or such.  The two-chip solution at the above address looks
interesting, but is for 10baseT (not 100).

 -Todd Peterson
  E-Lab Digital Engineering, Inc.

(816) 257-9954   FAX: (816)257-9945
http://www.elabinc.com

'Flash Card in Oz [EE]'
2000\05\23@024053 by David Duffy

flavicon
face
<x-flowed>Hi all,
Has anyone in Australia used flash cards with a PIC before?
I need about 16-32KB of flash memory as a removable card.
Farnell & RS have some stuff but way too expensive for me!
Anyone using something that's easy to get & fairly cheap?
Regards...

</x-flowed>

2000\05\23@025753 by David Huisman

flavicon
face
David,

Have you considered the DataFlash from Atmel ? These are serial addressable
and low cost.

Regards
David Huisman
Orbit Communications
http://www.orbitcoms.com
NSW
Australia

'[OT][EE] Phase locking DRO's'
2000\05\23@030620 by Robert Rolf

picon face
David Bengtson wrote:
> Well, you have a somewhat complex problem on your hand. You will need

Yes, it is that, but we're tackling it one piece at a time.
The hard/expensive part, getting big dishes, turned out to be the
easiest step, what with the DTH dishes displacing the BUDs.

> to end up building a Phase locked loop from the cheap DRO's that you
> have. You will also  need to come up with a very stable reference

Yes, that is the plan. Time and access to test equipment we have.
Thousands of dollars for commercial oscillators, we don't.
We also want others to be able to reproduce our work.

> oscillator. Here is a rough ASCII Diagram (Fixed Pitch Font, Please)
>
>   Ref--------Divider-------Phase-------Loop------DRO---------Stable RF
>   Osc.                     Detector    Filter         |
>                              |                        |
>                              |                        |
>                              |--- Divider-------------|
>
> This is the canonical block diagram of a Phase Locked loop. You have

Yes, I'm familiar with it. However, at microwave frequencies, the
output divider is exceedingly difficult to make. I'm looking at
some form of PIN diode sampler (like used in the old TEK 491 SA)
to do the phase detection. The hope is that the DRO's are stable
enough (100Mhz or so) that a good 100Mhz reference will hold them.

> the Section marked DRO, and you need to design a build the rest of it.

Yep, that is the challenge (and learning experience).
The key question I need to have an answer for it can the DRO's found
in consumer LNB's be voltage controlled over a sufficient range to
stay in lock over temperature (-40 to +70 like we get up here).

> Once you do that, you will be able to use this as a stable RF source
> for doing Radio Astronomy and Radio Interferometry. I have seen
> several web sites that talk about amateur radio astronomy, and a good
> web search will turn up several, including ones that talk about
> interferometry. I think that what you want to search for is Project
> Bambi. (I don't name them).

I am familiar with the various web sites. Most of the amateurs
are doing simple total power receivers or waveguide type
interferometers,
with relatively short (meters) baselines. We hope to do better, but
it's a long road yet. MIT has a very nice design built out of standard
parts, but they obviously have a -real- budget.


> GPS correletors are not the thing that you are looking for, although

That was a suggestion from a helpful PICLIST member.
However, the GPS RF chips are working around what would be our IF (since
the GPS industry makes the technology much cheaper to acquire). If one
supplied the 2nd dish signal as the 'chip', one -might- get a cheap
high frequency correlator. Obviously I'll have to look at the approach
in much more detail. Its just a wild thought at the moment.

> you could use a GPS receiver to help with the reference oscillator.

That is one option we are exploring. There is a nice design
(PIC based) that Brook Shera has put together to use the 1 PPS out of a
GPS. We're hoping to modify it a bit for WWVB reception (since it's
cheaper to build, [loopstick, bandpass crystal, op-amp and comparator]).

The plan is to come up with methods that amateurs can duplicate for
themselves without too much effort. Things like building your own
TCXO's with a 12Cxxx part as controller.

> The Accuracy of the reference oscillator determines the accuracy of
> the entire system.

Of course, although here it is more a case of STABILITY than accuracy.
We're not into sub megahertz spectral line analysis (yet), and the
DRO's will probably have too much jitter for that to work in any case.

Basic interferometry will work as long as both LOs are locked together,
but pumping 5150Mhz over 300 Meters (no waveguides) is no easy task. It
also doesn't allow for really wide baseline techniques to be developed.

> I would start with building one dish and then extending it to another
> one.

But one dish does not an interferometer make <G>.
I already do TPR radio astronomy twice a year, during sun-out season.


> This sounds like a fun project.

It's supposed to be. However, since I'm the only RF guy on the 'team'
I'm a bit overwhelmed by how much I have to do and yet learn, and
I need any help I can get to at get pointed in the right direction.
Why reinvent the wheel if someone has already done this sort of thing?

Thank you for your comments.

Anyone have any recommended texts/articles for 'real world', 'hands on'
microwave work? Something like "The Art of Electronics" at GHz.
What I've found to date has all be highly theoretical and not terribly
useful.

Robert.Rolf-at-ualberta.ca

'Flash Card in Oz [EE]'
2000\05\23@031242 by David Duffy

flavicon
face
<x-flowed>At 16:44 5/23/00 +1000, you wrote:
>David,
>
>Have you considered the DataFlash from Atmel ? These are serial addressable
>and low cost.
>
>Regards
>David Huisman
>Orbit Communications
>http://www.orbitcoms.com
>NSW
>Australia

Yes, they look great and are the right price but card format would
be better so customers can use them. (just poke it in the slot)
Regards...

</x-flowed>

2000\05\23@034017 by Mark Willis

flavicon
face
David Duffy wrote:
> At 16:44 5/23/00 +1000, you wrote:
> >David,
> >
> >Have you considered the DataFlash from Atmel ? These are serial addressable
> >and low cost.
> >
> >Regards
> >David Huisman
> >Orbit Communications
> >http://www.orbitcoms.com
> >NSW
> >Australia
>
> Yes, they look great and are the right price but card format would
> be better so customers can use them. (just poke it in the slot)
> Regards...

Drop the Flash into a small DE-09 shell;  only 9 pins are used by these
beasties, MACX., you can cut down if you try & read the docs;
Vcc, CS, SCK, SI, SO, WP, RESET, RDY/BUSY, Ground

(SI and SO can be shorted.  WP can be hardwired.  You can then double up
on Vcc and Ground.)

Makes a nice, small module swappable by Joe 10-Thumbs in the field.

(Might want to add protection diodes for some values of Joe 10-Thumbs.)

 Mark

2000\05\23@040209 by Mike Cornelius

flavicon
face
Hi David,

I've done some work with SmartMedia, problems are :-
It's quit hard to work with if you want it to be dos compatible (read is
easy write is a bitch on a device like a PIC only a little memory).
It's much larger than what you are looking for.
It's relativly expensive.

What about standard memory only (dumb) smartcards ?
They are cheap, readily avaliable, well supported, and pretty robust.
They tend to be EEPROM rather than flash, is this a problem ?

Regards,

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mike Cornelius                  Internet: @spam@mikespamspamKILLspambytethis.com.au
Byte This Interactive           Phone:    +61 2 9310-2157
PO Box 1342 Strawberry Hills    FAX:      +61 2 9319-3948
NSW 2012 Australia              URL:      http://www.bytethis.com.au
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


-----Original Message-----
From: pic microcontroller discussion list
[spamBeGonePICLISTRemoveMEspamEraseMEMITVMA.MIT.EDU]On Behalf Of David Duffy
Sent: Tuesday, 23 May 2000 4:37 PM
To: RemoveMEPICLISTKILLspamspamRemoveMEMITVMA.MIT.EDU
Subject: Flash Card in Oz [EE]


Hi all,
Has anyone in Australia used flash cards with a PIC before?
I need about 16-32KB of flash memory as a removable card.
Farnell & RS have some stuff but way too expensive for me!
Anyone using something that's easy to get & fairly cheap?
Regards...

'[OT][EE] Phase locking DRO's'
2000\05\23@043310 by Alan B Pearce

face picon face
How about the following scenario for your phase locking - I am thinking along
the lines of TV studio camera genlocking.

If each dish can have a DRO as a local oscillator to down convert the signal to
an IF frequency, and each DRO can be phase locked to a stable source. The stable
source is fed by coax or other suitable means - exactly how is unimportant so
long as it is still a stable signal at each dish. The local phase locked loop at
the dish has a means of injecting a stable DC voltage into the loop to provide a
constant phase offset to the oscillator signal. The control of this voltage is
done from a central point to get the IF signal received back at the central
point phase correlated to one of the other dishes which will be used as a
reference signal.

The control point will need a means of correlating each IF signal to the one
being used as a reference, and sending a command out to the phase control
voltage of all the other dishes. If the reference dish has an identical phase
control loop to the other dishes, it may also be possible to use this to adjust
for ageing or some other parameter which may make some of the other loops go
outside control range at extremes of phase angle difference. The Shera
electronics with modified control software would probably be the way to go.

P.S. I just received a couple of D/A converters from Analogue Devices (AD1861)
which are the equivalent of the Burr Brown ones Brooks Shera used, as I want to
build a copy of his frequency standard. I managed to get them as samples N/C!

Also using PICs in the control system, you could drop the OT.

'[EE] Re: Advice needed ==>PIC to PIC wireless tran'
2000\05\23@043340 by Kbek Tony

flavicon
face
Hi,
I've mentioned them before but here we go again:
http://www.nvlsi.no/

They have very easy to intergrate transiever modules.
I've used the old 9600 bps but I think they are available
in over 20kbps now.
Couldn't be easier.

/Tony


Tony KŸbek, Flintab AB            
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
E-mail: TakeThisOuTtony.kubekspamflintab.com
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ

'Flash Card in Oz [EE]'
2000\05\23@044203 by Brent Brown

picon face
> At 16:44 5/23/00 +1000, you wrote:
> >David,
> >
> >Have you considered the DataFlash from Atmel ? These are serial
> >addressable and low cost.
> >
> >Regards
> >David Huisman
> >Orbit Communications
> >http://www.orbitcoms.com
> >NSW
> >Australia
>
> Yes, they look great and are the right price but card format would
> be better so customers can use them. (just poke it in the slot)
> Regards...
>

I believe Atmel produces DataFlash on a card. Simple solution as
smart card sockets are easy and cheap to get even from Farnell or
RS. Atmel gave me a big fat no reply last time, interesting to see if
you come up with something.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile: 025 334 069
eMail:  spamBeGonebrent.brownKILLspamspamTakeThisOuTclear.net.nz

'[OT][EE] Phase locking DRO's'
2000\05\23@052541 by Pavel Korensky

flavicon
face
At 01:04 23.5.2000 -0600, you wrote:
>
>That is one option we are exploring. There is a nice design
>(PIC based) that Brook Shera has put together to use the 1 PPS out of a


I made it (with small modification - Lattice PLD chip instead the LSI
logic) and it works really good. I am using it as a master timebase
reference for my various instruments.

But oscillator is a real problem. I tried couple of TCXOs and results was
not good. Finally I bought the OCXO (expensive) and results are much much
better.
Currently, I am trying to make my own OCXO as a hobby project.

>The plan is to come up with methods that amateurs can duplicate for
>themselves without too much effort. Things like building your own
>TCXO's with a 12Cxxx part as controller.

Look at http://www.karlquist.com  - Rick Karlquist was developping OCXOs for
Hewlett-Packard and he knows a lot about the whole problem. On his pages,
there is a very nice and detailed design of ultra high precision OCXO
(which I am trying to duplicate at home). The whole design is patented, but
I got the permission from Rick to use the design for non-profit projects
(because HP is not currently actively using this patent in any design).

The whole oscillator is a bit complex to make (you need lathe and mill),
but the result should be perfect. BTW, he is using PIC16C73 for the PID
control of the oven temperature.

Best regards

PavelK

**************************************************************************
* Pavel KorenskyÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
* DATOR3 LAN Services spol. s r.o.ÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
* Styblova 13, 140 00, Prague 4, Czech Republic      ÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
*ÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
* PGP Key fingerprint:Ê F3 E1 AE BC 34 18 CB A6Ê CC D0 DA 9E 79 03 41 D4 *
*ÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
* SUMMA SCIENTIA - NIHIL SCIREÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊ *
**************************************************************************

'[EE] Re: Advice needed ==>PIC to PIC wireless tran'
2000\05\23@053617 by Vasile Surducan

flavicon
face
On 23 May 00, at 10:19, KŸbek Tony wrote:

> Hi,
> I've mentioned them before but here we go again:
> http://www.nvlsi.no/
>
  Ok but that's with money! Some free ideas ?
 I saw something about two 16f877 connected on radio link
 It's something visible on net ?
 Vasile

****************************************
Surducan Vasile, engineer
email:EraseMEvasile.....spamKILLspaml30.itim-cj.ro
URL:http://www.geocities.com/vsurducan
****************************************

2000\05\23@061636 by Kbek Tony

flavicon
face
>   Ok but that's with money! Some free ideas ?
>  I saw something about two 16f877 connected on radio link
>  It's something visible on net ?
>  Vasile

:-) , there are no such thing as free lunch, one way
or the other one must build something, that manages to
communicate by means of RF. using the chips above would
save you alot of hassle ( not to mention avoiding illegal
RF band usage ). And, trust me, these are VERY cheap
concidering bang for the buck. ( if I recall correctly
something around $10 each ).
About three wires to connect, Din, Dout, Txenable.
And, just checked it, they are at 20kbps, FSK modulated,
standby 8uA, tx 8mA, two channels etc.

Could it be any easier ?



Tony KŸbek, Flintab AB            
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
E-mail: spamtony.kubekspamflintab.com
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ

'Flash Card in Oz [EE]'
2000\05\23@070004 by David Duffy

flavicon
face
<x-flowed>At 12:38 AM 5/23/00 -0700, you wrote:
{Quote hidden}

Already thought about that one but customer not fussed on a D socket on
front panel.
Too much chance of some end user plugging something else in to it!
Otherwise, that was my number one idea of the day...

</x-flowed>

2000\05\23@070018 by David Duffy

flavicon
face
<x-flowed>At 08:40 PM 5/23/00 +1200, you wrote:
> > At 16:44 5/23/00 +1000, you wrote:
> > >David,
> > >
> > >Have you considered the DataFlash from Atmel ? These are serial
> > >addressable and low cost.
> > >
> > >Regards
> > >David Huisman
> > >Orbit Communications
> > >http://www.orbitcoms.com
> > >NSW
> > >Australia
> >
> > Yes, they look great and are the right price but card format would
> > be better so customers can use them. (just poke it in the slot)
> > Regards...
> >

Brent Brown wrote;
>I believe Atmel produces DataFlash on a card. Simple solution as
>smart card sockets are easy and cheap to get even from Farnell or
>RS. Atmel gave me a big fat no reply last time, interesting to see if
>you come up with something.

Hmmm... I didn't notice them on the Atmel site last time. I might go &
have a look again. Maybe ACD in Melbourne can do a P&A for us?
Farnell & RS have plenty of fairly contact assemblies but no cards!
If anyone's interested I will let the list know what's out there.
Regards...

</x-flowed>

2000\05\23@070617 by David Duffy

flavicon
face
<x-flowed>Hi Mike,
No need for DOS compatibility - the data is custom.
Flash or EEPROM makes no difference - non volatile is what I need.
The smart card I've seen so far are quite small... 2K-bits (256 bytes)
I need about 16K-bytes or more to store all of the data required.
The data doesn't change very often. (maybe every 30/60  days or so)
Needs to plug into customers equipment with no hassles at all.

At 06:00 PM 5/23/00 +1000, you wrote:
{Quote hidden}

>{Original Message removed}

'[OT] [EE] Unfused printouts <-- PC board transfer'
2000\05\23@085716 by Russell McMahon

picon face
Here's a trick which MAY be useful. Like all the best ideas, I discovered it
by accident - in this case while trying to print an envelope short side in.

If you cut a sheet of paper to less than a certain length (the exact length
will vary with your printer) and feed it to a laser printer, then the feed
rollers after the toner deposition stage will (may?) fail to pick it up and
the paper will stop in the midst of the printer without having been fused.

I have an old HP4L that I normally use and if I feed it a half sheet it sits
nicely in the printer until I remove the toner cartridge and take it out.
You now have an unfused smudge free copy waiting to be transferred to
something else.

I haven't tried this for PCB work but I have used it to transfer toner to
mugs and then baked them in a domestic oven to produce a surprisingly robust
finish.
I have also transferred pictures from a scanner to a plastic surface by this
method.
YMWV

This would be very easy for someone to try for PCB purposes - if you do
please  let us know the results!

You could perhaps get a similar result by depowering the fuser roller (or
removing it ?) but this would be much harder to do and much more liable to
smudge.


     Russell McMahon
_____________________________

>From other worlds - http://www.easttimor.com
                               http://www.sudan.com

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))


{Original Message removed}

2000\05\23@085720 by Russell McMahon

picon face
Here's a trick which MAY be useful. Like all the best ideas, I discovered it
by accident - in this case while trying to print an envelope short side in.

If you cut a sheet of paper to less than a certain length (the exact length
will vary with your printer) and feed it to a laser printer, then the feed
rollers after the toner deposition stage will (may?) fail to pick it up and
the paper will stop in the midst of the printer without having been fused.

I have an old HP4L that I normally use and if I feed it a half sheet it
receives the image and then sits
nicely in the printer until I remove the toner cartridge and take it out.
You now have an unfused smudge free copy waiting to be transferred to
something else.

I haven't tried this for PCB work but I have used it to transfer toner to
mugs and then baked them in a domestic oven to produce a surprisingly robust
finish.
I have also transferred pictures from a scanner to a plastic surface by this
method.
YMWV

This would be very easy for someone to try for PCB purposes - if you do
please  let us know the results!

You could perhaps get a similar result by depowering the fuser roller (or
removing it ?) but this would be much harder to do and much more liable to
smudge.


     Russell McMahon
_____________________________

>From other worlds - http://www.easttimor.com
                               http://www.sudan.com

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))


{Original Message removed}

'[EE] Adjusting voltage output of a temperature sen'
2000\05\23@095515 by Scott Dattalo

face
flavicon
face
On Tue, 23 May 2000, Damon Hopkins wrote:

> Dean Biddle wrote:
> >
> > Hi,
> >
> > Are there alternative(s) to an operational amplifier (supplied by +ve and
> > -ve) to adjust the voltage output of an LM335 temperature sensor from
> > approx. 2.5 to 3.5 volts to span the 0 to 5 volt range for a P16F87x A/D
> > converter?  My application needs to consume minimal current and preferably
> > use only one battery.  Can another option for the configuration of the A/D
> > system be used other than limiting Vref+ to approx. 3.5 volts?
> >
> > I assume this is common, so please simply refer me to a relevant past
> > PICLIST thread if I failed to match the thread in my "pre-post" search.
>
> Excellent question.. I await the answer because right now I'm using an
> OP AMP to do it... I hope there is..

Is it the op amp that's the problem or having to supply -ve? There are several
low-power, single-supply, rail-to-rail opamps in tiny SOT-23 sized packages that
would work nicely here.

All though I've never explored this, you could recover the A/D converter's
dynamic range by tying the LM335 to the 87x's vref pin and then measure a known
DC voltage source on one of the analog inputs. Perhaps two or three DC voltages
could be used as references. At first glance this would appear to prevent the
other analog inputs from being used. However, you could still switch the A/D to
use the power supply rails as the voltage reference.


Scott

'Flash Card in Oz [EE]'
2000\05\23@113009 by Bob Blick

face
flavicon
face
> Has anyone in Australia used flash cards with a PIC before?
> I need about 16-32KB of flash memory as a removable card.

Saw a web site that used flash, an Atmel micro, and the MAS3507/DAC3550
combo to make an mp3 player.

The flash he used was "Compact Flash" which is one of the two varieties
used in cameras, the smaller of the two. It is 3.3 volts and easy to talk
to. He showed a cool connector scheme. I'll try to dig up the address.

Unfortunately a lot of it will go to waste if all you need is 32k, these
start at 4 megabytes for about US$15 each.

-Bob

'[OT] [EE] Unfused printouts <-- PC board transfer'
2000\05\23@122027 by Damon Hopkins

flavicon
face
Russell McMahon wrote:
{Quote hidden}

> {Original Message removed}

2000\05\23@123446 by Alan B Pearce

face picon face
>I wonder if it would smudge if you just put a switch on the power supply
>line to the fuser element.. then you could let the paper print manually
>but not fuse it to the paper.. you could print stuff on anything that
>would fit in the printer slot then... It'd probably smudge though..

>From my experience with servicing laser engines, I would say what will happen is
some of the toner will collect on the fuser roller because it is not being fused
into the paper, and then will produce repeat patterns along the paper over the
rest of the image, right where you do not want it. I would like to try Russell's
idea, though possibly taking it one step further. How about charging up the
surface of the laminate in a similar manner to the method used by a laser
printer to charge the image roller, and then shine the image direct onto the
laminate. Pass the laminate through something which will drop toner onto it a
bit like a continuous flow chocolate machine, and then direct fuse the toner to
the laminate. Yeah, I know it is cloud cuckoo land, as it will not be possible
to discharge parts of the laminate using the image because it is a copper sheet
instead of a silicon roller, but it would save some image stretching problems.

'Flash Card in Oz [EE]'
2000\05\23@140636 by Octavio Nogueira

flavicon
face
> Hi Mike,
> No need for DOS compatibility - the data is custom.
> Flash or EEPROM makes no difference - non volatile is what I need.
> The smart card I've seen so far are quite small... 2K-bits (256 bytes)
> I need about 16K-bytes or more to store all of the data required.
> The data doesn't change very often. (maybe every 30/60  days or so)
> Needs to plug into customers equipment with no hassles at all.

MultiMedia memory card is easy to interface, you can
use SPI mode, available at http://www.sandisk.com

Friendly Regards

Octavio Nogueira
===================================================
nogueiraSTOPspamspamKILLspampropic2.com                  ICQ# 19841898
ProPic tools - low cost PIC programmer and emulator
http://www.propic2.com
===================================================

----- Original Message -----
From: David Duffy <@spam@avd.....spamspamUQ.NET.AU>
To: <spamPICLIST.....spam.....MITVMA.MIT.EDU>
Sent: Tuesday, May 23, 2000 6:58 AM
Subject: Re: Flash Card in Oz [EE]


{Quote hidden}

> >{Original Message removed}

'[OT][EE] Phase locking DRO's OCXOs'
2000\05\23@160143 by Robert Rolf

picon face
> >That is one option we are exploring. There is a nice design
> >(PIC based) that Brook Shera has put together to use the 1 PPS out of a
>
> I made it (with small modification - Lattice PLD chip instead the LSI
> logic) and it works really good. I am using it as a master timebase
> reference for my various instruments.

Huh? The QST article I'm working from doesn't have a PLD (that I can
recall). It used discreet logic for everything. Is there a more
current design that I've obviously not seen? It would make sense to
use a PLD to simplify the construction (lots of dividers at al).

> But oscillator is a real problem. I tried couple of TCXOs and results was
> not good. Finally I bought the OCXO (expensive) and results are much much
> better.
> Currently, I am trying to make my own OCXO as a hobby project.

Then I guess we had better have an off-line chat.

> >The plan is to come up with methods that amateurs can duplicate for
> >themselves without too much effort. Things like building your own
> >TCXO's with a 12Cxxx part as controller.
>
> Look at http://www.karlquist.com  - Rick Karlquist was developping OCXOs for

EXCELLENT collection of info. Thanks. Knowing that we could borrow a
really good reference I was leaving that part for later.

> Hewlett-Packard and he knows a lot about the whole problem. On his pages,
> there is a very nice and detailed design of ultra high precision OCXO
> (which I am trying to duplicate at home). The whole design is patented, but
> I got the permission from Rick to use the design for non-profit projects
> (because HP is not currently actively using this patent in any design).

Really? With 9 other 'inventors' how can just ONE give permission to
use the patent?
http://www.patents.ibm.com/details?&pn=US05729181__

> The whole oscillator is a bit complex to make (you need lathe and mill),

Not a problem for us, or serious amateurs I would think.

> but the result should be perfect. BTW, he is using PIC16C73 for the PID
> control of the oven temperature.

Yes, that keeps us ON topic I guess.

Robert.Rolf-at-UAlberta.ca

2000\05\23@161021 by Robert Rolf

picon face
Alan B Pearce wrote:
> constant phase offset to the oscillator signal. The control of this voltage is
> done from a central point to get the IF signal received back at the central
> point phase correlated to one of the other dishes which will be used as a
> reference signal.

As I understand it, this is approximately how it's done. One also has
to match the cable delays to within an IF wavelength. One also
introduces
an 'offset' in the LO to accommodate the look angle and it's effects
on path length.

> outside control range at extremes of phase angle difference. The Shera
> electronics with modified control software would probably be the way to go.

We're hoping its adaptable to the task. Why reinvent the wheel?

In theory one doesn't even need a D/A, just PWM and a LPF.

Robert.Rolf-at-ualberta.ca

'[OT] [EE] Unfused printouts <-- PC board transfer'
2000\05\23@162058 by Robert Rolf

picon face
This is EXACTLY how the very first XEROX copier worked. It used
a flat piece of metal, coated with selenium, and had a series of
'stations' that you moved the plate through to charge, expose, coat with
toner (flour shaker style), laminate, and fuse (bake). Saw this on a
Discovery Channel program. 1'x1'x3' high desk top office copier. Could
only do single sided pages since the expose cycle was done through the
back of the page. Took about 3 minutes to complete so it didn't get too
far in the marketplace. Then they perfected the continous feed 8511
copier and the
rest is history.

Alan B Pearce wrote:
{Quote hidden}

'[OT] [EE] PC board transfer paper play'
2000\05\23@164800 by Sten Dahlgren

picon face
There is a teflon coated fiber cloth used in baking bread used instead
of
"owen paper". Hopefully you understand what i mean.

/Sten

Mark Willis wrote:
{Quote hidden}

'[EE] compact flash spec'
2000\05\23@171137 by mike

flavicon
picon face
I found the following link in another NG, it may be of interest for
people interfacing to compact flash cards.
http://www.compactflash.org/cfspc1_4.pdf
its about 550k
cheers Mike W

'Flash Card in Oz [EE]'
2000\05\23@184009 by Mark Willis

flavicon
face
David Duffy wrote:
{Quote hidden}

OK, how about this then.  DigiKey has 10-pin 2mm sockets for $1.29 in
onesies (3m1010-ND, page 37)  Strip headers for $1.04 lower on the same
page.  Solder the 2mm socket onto your PC board with the Flash, and
encapsulate with any of a number of different goodies in a nice
rectangular blob shape to fit the front panel (Ask me off list if you
don't have favorites there, or want brainstorming.)  That'll do it <G>

 Mark

--
I re-ship for small US & overseas businesses, world-wide.
(For private individuals at cost; ask.)

'virtual car. Gen locking [OT][EE]'
2000\05\23@200831 by Robert Rolf

picon face
Richard Ottosen wrote:
> >From what I understand, the color locking is the hard part. I was once

If you want to dissolve between two camera signals, yes, it is difficult
to get the phase lock down to the sub degree range required.

> told that half of the circuitry in the color cameras I borrowed was the
> video locking function. This may no longer be true with the changes in
> technology.

An exaggeration. I've been in video for 20 years. While substantial
effort
is needed for broadcast grade locking (10% at most) your alternating
field/frame approach does not require it. Gen locking adds about $50 to
the
cost of a $300 CCD color camera. A lot of the chip sets support it
directly, just add the jack and coupling cap/resistors.

The funny thing is, the new broadcast switchers don't need 'timed'
camera sources anymore. It's all done digitally now, so ANY source
(including sloppy VCR's) will do.

> One change in technology I need to explore is inexpensive time base
> correctors. With picture-in-picture built into TV's and frame capture
> cards for PC's I expect it would not be that hard to make a simple TBC.

It isn't. $150 per channel for a dual channel TBC for a PC (DPC systems
in Montreal?). Just look in any of the consumer 'Desk Top Video'
magazines
for adverts. Signetics/Philips makes several chips that will do the job
outright.

Ironically a PIP video card is already doing 'frame synching' (which is
actually a lot harder than simple Time Base Correction). The kick is
that the VGA card is running 60-80FPS non interlaced vs NTSC's 30 with
interlace.

Also realize that a cheap TBC many only provide a few (5-10) lines of
'correction' and will not have a enough range to 'frame lock' unless
it explicitly says that it is a 'full frame' TBC.

You realize that you only need ONE frame synchronizer to do what you
want? You use one camera as the reference that the other is locked to.
HOWEVER, having done this, I found that one could perceive the slight
difference in timing between the two eyes when the cameras were quite
out of sync. True NTSC is a 4 field sequence so you could see up to 67mS
of delay between the two eye views.
You really DO want to lock the _camera_ scans to remove this 'headache'
[literally]. If you don't, fast pans will make the image jump in and
out in depth as one eye sees the same image 67 mS before the other.

In fact, this is exactly the technique used by the infamous super bowl
3D of several years ago. The darkened eye has a slower visual response
and so fast left right object motion gave the illusion of depth.
And for this exploit the perpetrators got a million bucks?

> Obviously some pretty fancy chips exist that could make it possible. Oh,
> so many projects and so little time ;-)

I know EXACTLY what you mean.

BTW the NASA technical channel (Tr5, G2 85dW) does time division
multiplexing of the various cameras on the cape in the hours prior to
launch.
A digital VCR with 'strobe' function can usually separate out the
two streams into something more viewable. It's awesome being inches away
from the external fuel tank as they do a systematic inspection of it's
surface. It's also pretty cool to be looking over the astronauts
shoulders
as they work.

NASA tv is available on the web as Realvideo or Mediaplayer formats by
drilling down from:
http://www.nasa.gov/ntv/

{Quote hidden}

'[EE] PC board transfer'
2000\05\24@011706 by Ing. Marcelo Fornaso

flavicon
face
Hi,
I'd like to invite you all to a description of my poor's man method for PCB making.

http://www.sysameri.com/marcelo/placa.htm

I hope it to be useful for at least some of you, and I beg you please to send comments and corrections to my english to help me to improve the page readability.
Thank you.

Marcelo Fornaso

'[OT][EE] Phase locking DRO's'
2000\05\24@035232 by Alan B Pearce

face picon face
>One also has to match the cable delays to within an IF wavelength. One also
>introduces an 'offset' in the LO to accommodate the look angle and it's effects
>on path length.

Perhaps it did not come across clearly enough in what I wrote, but I envisaged
that these could be taken care of by the phase offset of the LO. I guess the
problem here is the cable length can be significantly more than 360 degrees at
the LO frequency! Certainly I expected to be able to adjust the look angle
factor with the LO, but I guess the physical spacing again becomes more than 360
degrees.

>In theory one doesn't even need a D/A, just PWM and a LPF.

I would have thought this could introduce a heap of unwanted sidebands on the LO
due to filtering difficulties. Also I figured that the D/A would have much finer
control steps for the LO, without going through the math of just how fine they
may need to be.

'[OT] [EE] Unfused printouts <-- PC board transfer'
2000\05\24@095230 by Dale Botkin

flavicon
face
On Tue, 23 May 2000, Damon Hopkins wrote:

> Russell McMahon wrote:
> > You could perhaps get a similar result by depowering the fuser roller (or
> > removing it ?) but this would be much harder to do and much more liable to
> > smudge.
>
> I wonder if it would smudge if you just put a switch on the power supply
> line to the fuser element.. then you could let the paper print manually
> but not fuse it to the paper.. you could print stuff on anything that
> would fit in the printer slot then... It'd probably smudge though..

You'll also have to dummy up the fuser temperature sensor, probably along
with a few others. The laser printer will be very reluctant to print if it
sees anything unusual in the way of fuser temperature, fuser heater
continuity, etc.

Actually, a Xerox 4045 might not be bad for this.  It didn't use a fuser
roller, it used a fuser lamp that fused the toner with radiant heat, no
pressure.  Of course, everything ELSE about the 4045 is such a total,
absolute nightmare, plus they have extremely limited graphics capability.
Well, that and you'll need extra supports for your desk...

Dale
---
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
               -- Isaac Asimov

'[EE] PC board transfer'
2000\05\24@100114 by tt, Gary

flavicon
face
Marcelo,


Excellent job!  I use the same technique outlined on your website.  The only
difference in my technique is to put something heavy and flat on the board
after heating it with the iron and letting it cool with the heavy weight on
the board for about 15 minutes.  I then put it in water and continue with
the steps you outlined.

Thanks again for sharing your information.



       ----------
       From:  Ing. Marcelo Fornaso [SMTP:KILLspammfornasospam_OUTspamINFOVIA.COM.AR]
       Sent:  Wednesday, May 24, 2000 1:15 AM
       To:  spam_OUTPICLISTspamTakeThisOuTMITVMA.MIT.EDU
       Subject:  [EE] PC board transfer

       Hi,
       I'd like to invite you all to a description of my poor's man method
for PCB making.

       http://www.sysameri.com/marcelo/placa.htm

       I hope it to be useful for at least some of you, and I beg you
please to send comments and corrections to my english to help me to improve
the page readability.
       Thank you.

       Marcelo Fornaso

'[EE]: 120VAC Traces'
2000\05\24@103818 by frmiller

flavicon
face
I have a board that I recently redesigned that contains nine
T90 relays that switch 110VAC. The board goes in an
industrial controller and switches lights and contactors
(mag starters). The relays all have flyback diodes across
the coils and snubbers across the contacts.

On the old version of the board (not my design), the 110VAC
traces were mixed on the board with signal traces. It
worked, but as you can imagine, we had problems in the
field. I tried to eliminate the problem by aligning the
relays so that the 110VAC traces were all on the lower area
of the board and all other traces were along the upper.
There is a "no trace zone" about .6" wide that runs under
the relays between the coil pins and the contact pins. This
is the dividing line between the 110VAC area and the rest of
the board.

This layout helped a lot, but I'm still getting a few spikes
back in the signal traces. It is sometimes enough to lock up
the NE5090 mux on the board, especially when the contactors
fire. I have bypass caps on the chips on the board, but I
really would like to eliminate the spikes.

The whole point of this long-winded explanation is to ask if
filling the "no trace zone" with a ground plane would do any
good. If so, should it be earth ground or circuit ground? Is
there any way to hack a current board (adding foil or
something) to simulate the ground plane that would give
meaningful test results before we redo the board? The board
is two-sided, through hole.

TIA,

Ryan

'[OT]: [EE]: PIC + USB'
2000\05\24@105050 by Severson, Rob

flavicon
face
Jim,

I can't help with the Mac driver aspect of your problem, but I made USB
hardware that is aimed at what you need to accomplish. The USBSIMM
(http://usbsimm.home.att.net) paired with a Dontronics (http://www.dontronics.com)
relay board will get you the hardware that you need. If the Mac supports the
HID devices then example firmware is also available.

My blurb:
The USBSIMM provides a method to interface various circuit designs to the
Universal Serial Bus. Compliance with the SimmStick(tm) format provides the
benefit of quick and easy adaptation to SimmStick(tm) products. The USBSIMM
card will allow rapid product development without the initial cost of USB
development tools.

USBSIMM contains an advanced 8051 with a USB serial interface engine. The
microcontroller has 8k bytes of RAM internally, and is supplemented with 32k
bytes of external RAM. The microcontroller sports two serial ports, several
timers, an I2C engine, and 16+ port lines. This makes for a rather powerful
SimmStick or small embedded control computer even if the USB port is used
only for development.

Jim, this is a powerful little chunk of hardware that should work for you.
I'd like to be able to add Mac application information to the website.
Contact me if you would be willing to share your work.

-Rob




> {Original Message removed}

'[EE] PC board transfer'
2000\05\24@111350 by Ing. Marcelo Fornaso

flavicon
face
By the way: The prototype is a 16F84 based RF transmitter running at 310 MHz. Kind of beacon sending telemetry at 2400 bauds.

http://www.sysameri.com/marcelo/placa.htm

Regards
Marcelo Fornaso

'[EE]: 120VAC Traces'
2000\05\24@130031 by Dan Michaels

flavicon
face
Ryan Miller wrote:
>I have a board that I recently redesigned that contains nine
>T90 relays that switch 110VAC. The board goes in an
>industrial controller and switches lights and contactors
>(mag starters). The relays all have flyback diodes across
>the coils and snubbers across the contacts.
.......

Hi Ryan, for several years I consulted with a company that built
industrial controllers that switched multiple 220 VAC inductive loads.
They sold 1000s of these units each year, and saw every manner of
failure. Many previous comments by other picisters have indicated
that 1 or 2 things might fix this sort of problem, but in my
experience, we found it required multiple lines of attack and each
was only marginally effective. A heavy inductive switching environment
is probably the very worst place into which to put a microprocessor,
and I think the best results come from an overall systems-level
approach - which of course involves 20 or 30 or 60 aspects.

That being said, let me relate some of the most effective methods
in my experience:

1. EMI and spike filters at the hiVAC power input - series EMI filter,
  MOVs, etc.
2. EMI/spike filtering on the power supplies - "transient voltage
  suppressor" diodes [eg, Microsemi 1.5KE series] on the P/S input side,
  downstream of the AC transformer, if there is one.
3. Bypass caps, of course, at all the usual points.
4. Of course, diodes across the relay coils and snubbers across relay
  contacts.
  NOTE - some loads produce significantly worse switching transients
  than others, so the same snubber may not be universally effective.
  When looking across the contacts, you will see hi-speed spikes [bad]
  riding on a slower wave [normal] in cases where the snubber is not
  effective enough. You might want to use an isolation xfrmr to do
  this measurement.
  NOTE - one thing you can do is sniff around with a scope probe,
  ungrounded, to measure presence of EMI, and determine what it is
  correlated to.
5. On the low-level signal lines, RC filters and transorbs [transient
  voltage suppressor diodes, which are essentially low-inductance
  zeners] are effective. Note - we ended up putting transorbs on
  practically ever signal line - and regular zeners are too slow here.
6. Layout issues - physically separate hi/low V, and signal/switching
  circuitry. Separate power busses and gnd planes [if possible]. Don't
  run different lines near each other, and don't cross them.
7. Use watch dog timer in uC s.w. Use debounce routines on signal
  measurements.
8. Use digital bus crowbar ckt in cases where chip latchup is an
  especially bad problem. [Note - the watchdog will not fix latchup].

There are probably a few others which I forget.
==============

>
>The whole point of this long-winded explanation is to ask if
>filling the "no trace zone" with a ground plane would do any
>good. If so, should it be earth ground or circuit ground? Is
>there any way to hack a current board (adding foil or
>something) to simulate the ground plane that would give
>meaningful test results before we redo the board? The board
>is two-sided, through hole.
>

Regarding gnds, the digital, analog, switching, and switched
should be as physically and electrically separate as possible,
and should be connected at "one point" as close to the power
entry point of the board as possible. The more current, the larger
the trace/wire.

Regarding hacking the test bd, try using aluminum duct tape
grounded back to the hiV side [looks like relay power in this case].
In essence, you are putting a guard ring around the hiV side which
is intended to contain the internal fields. Likewise, you can
put a gnd guard ring around each other subsystem, connected to
the gnd of that subsystem.

Hope this helps,
- Dan Michaels
Oricom Technologies
http://www.sni.net/~oricom
==========================

'virtual car. Gen locking [OT][EE]'
2000\05\24@130650 by rottosen

flavicon
face
Robert Rolf wrote:
>
> Richard Ottosen wrote:
> > >From what I understand, the color locking is the hard part. I was once
>
> If you want to dissolve between two camera signals, yes, it is difficult
> to get the phase lock down to the sub degree range required.
>
> > told that half of the circuitry in the color cameras I borrowed was the
> > video locking function. This may no longer be true with the changes in
> > technology.
>
> An exaggeration. I've been in video for 20 years. While substantial
> effort
> is needed for broadcast grade locking (10% at most) your alternating
> field/frame approach does not require it. Gen locking adds about $50 to
> the
> cost of a $300 CCD color camera. A lot of the chip sets support it
> directly, just add the jack and coupling cap/resistors.


What you say here does show how much the technology has changed. The
cameras I used were "remote head" units with the CCD imager at the end
of a cable connected to a controller that was about the size of a
paperback book. Each of the two cameras we used for the stereo video
cost about $1200 US at the time (about 1990 I think).


{Quote hidden}

In fact one plan I considered was to put together a bare bones single
board PC and a off the shelf frame capture/TBC card to do video 3-D. Not
the cheapest way to go but it could be quick and easy.


{Quote hidden}

That does sound tricky making such different videos come together on one
display!


>
> Also realize that a cheap TBC many only provide a few (5-10) lines of
> 'correction' and will not have a enough range to 'frame lock' unless


I didn't know there was such a thing. It would be a big ouch to buy one
of these and THEN find out.


{Quote hidden}

I guess the TBC solution will not work very well from what you say. Too
bad. Do you see any way around this problem? May lock both cameras using
a dual TBC?


{Quote hidden}

Thanks for all the ideas


-- Rich


{Quote hidden}

'[EE]: 120VAC Traces'
2000\05\24@131740 by Chris Eddy

flavicon
face
Ryan;

This subject came up just a few weeks ago.  The relay contacts are
generating EMI with a spark.  You need to use a snubber, just a cap, or
some other means to quench the arc on the contacts.  See the archive.

Chris Eddy

Ryan Miller wrote:

> I have a board that I recently redesigned that contains nine
> T90 relays that switch 110VAC. The board goes in an

2000\05\24@132805 by Dan Michaels

flavicon
face
BTW, a good book on this topic is

"Noise Reduction in Electronic Systems" by Henry Ott

2000\05\24@133156 by Spehro Pefhany

picon face
At 06:16 AM 5/24/00 -0400, you wrote:
>Ryan;
>
>This subject came up just a few weeks ago.  The relay contacts are
>generating EMI with a spark.  You need to use a snubber, just a cap, or
>some other means to quench the arc on the contacts.  See the archive.

He said he has snubbers on there.

Part of the problem is the type of relays used. This is a very complex
subject. The closest thing to a magic bullet is to go multilayer.

Best regards,


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Spehro Pefhany --"it's the network..."            "The Journey is the reward"
.....speff.....spamRemoveMEinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

2000\05\24@134432 by Dan Michaels

flavicon
face
Always the stuff forgotten the first time [or 6]:

One way to tell if a gnd plane will be effective in a particular
situation is to simply place a grounded metal plate close to the
underside of the circuitry in question [insulated from it of
course], and note the effects. Use a short, thick gnd lead directly
to the cktry being shielded. I have used this method to determine
where gnd planes are most effectively added onto 2-sided pcbs.

- Dan Michaels

'[EE][OT] Impedance Matching a Phone Line'
2000\05\24@145247 by Clark, John

flavicon
face
I am trying to connect the output of a D/A signal to an open phone line to
play audio (sort of similar to the "DTMF decoding with a PIC" thread that is
going on, only I need to transmit DTMF and music).  I have been doing quite
a bit of searching for specifications on telco line impedance and so forth,
but I have yet to find a definitive guide.  I am also strongly leaning to
finding a 3rd party product that would accept a standard 47K ohm impedance
signal from an RCA phono plug shielded type of connector.  If anyone has
information, especially on the latter, I would really appreciate it.

Thanks.


John Clark
Indianapolis, IN

'Boosting power of radio modules[EE]'
2000\05\24@150945 by Andrew Seddon

picon face
I have purchased a couple of radio transceiver modules from
http://www.radiometrix.com however the rated output power is a tad on the low side.
Now I know the legal issues about boosting power but I am in the middle of
no-where and I am only talking about a little power increase. The modules
work at 433.92Mhz and output 6dbm(is that a good measure of power? I have no
RF experience). They are half duplex and the TX/RX works off the same
antenna. I was wondering if it would be possible to maybe place a transistor
and a resistor in place of the antenna to boost the power.

Any help appreciated.

2000\05\24@171050 by l.allen

picon face
Andrew Seddon wrote:

> I have purchased a couple of radio transceiver modules
>from http://www.radiometrix.com however the rated output
>power is a tad on the low side.
> Now I know the legal issues about boosting power but I
>am in the middle of no-where and I am only talking
>about a little power increase. The modules
> work at 433.92Mhz and output 6dbm(is that a good
>measure of power? I have no RF experience). They are
>half duplex and the TX/RX works off the same antenna. I
>was wondering if it would be possible to maybe place a
>transistor and a resistor in place of the antenna to boost
>the power.
>
> Any help appreciated.

There are 3 solutions..
Boost the Rx sensitivity, boost the Rx sensitivity and
boost the Rx sensitivity.

This is FAR more effective than increasing the Tx power
"a bit". Doubling the output power of the Tx will increase
the RF power 3dB BUT you with a little care you will get
much more than 3 dB increase in sensitivity in the Rx
path without violating transmission laws.

The most obvious first choice would be a signal boost
preamp on the input to the Rx (since a directional
antenna will violate the power level spec and directional
may be unacceptable anyway).

There are a sea of published projects and kits fitting this
description available.... a UHF preamp/booster.
One of my local electronics stores sells a wideband
antenna amplifier for $30 (US$15) that covers 30 to
850MHz at 20dB boost.

The only potential gotcha is the Tx signal overloading the
booster amp but that is not likely at those power levels.
The easiest solution in that case would be a separate Rx
antenna otherwise you are into RF territory of selective
stages, filters, traps etc.


_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

2000\05\24@172134 by Quitt, Walter

flavicon
face
On RX Preamps watch out for how much noise
is generated by it.  EX: A cheap broadband
preamp with a noise floor of 6DB wiil actually
make the reception worse as your weak received
signal will fall below the noise floor.  Not
good.  Get a good UHF low noise preamp.  433 is
close enough to the ham bands that you should
be able to get one for amateur radio use
that will do real well.

{Original Message removed}

'[EE]: Impedance Matching a Phone Line'
2000\05\24@173809 by Brian Hopkins

flavicon
face
John:
Telco subscriber loops (twisted pair cable) have a nominal characteristic
impedance (Z) of 900 ohms. That is the classic comprise number used when
designing subscriber side equipment, and why all the CO line simulators
(artificial lines) use that value.
This of course is not the DC loop resistance (R) which will depend on your
distance from the CO and the gauge of cable in your loop makeup.
So..if you design your line drive electronics to have an output impedance of
900 ohms you should have maximum power transfer, and minimize reflections
(echo) for... most.... average...typical ... loops your equipment may
connect to.
I can't find any of my tech college references, but these sites confirm what
I recall was drilled into me.
www.mnm.com.sg/measurement/teltone/tls5.htm
teltone.com/telecom_solutions/test_tools/test_tls-3a_specs.html
http://www.wilcominc.com/t240.htm
http://www.egyed.com/phonework.html

Any references you see to 600 ohms (Z) relate to 'open wire' , used for toll
circuits (open wire carrier) in the pre-microwave days which were the
pre-fibre optic days. The equipment side of the telco was designed to match
that 600 ohms.
Old standards...old history...

Brian Hopkins

{Original Message removed}

'[EE]: 120VAC Traces'
2000\05\24@180514 by frmiller

flavicon
face
Thanks for your reply, Dan. Comments interlaced:

> Dan Michaels wrote:
>
<snip>
>
> That being said, let me relate some of the most effective
methods
> in my experience:
>
> 1. EMI and spike filters at the hiVAC power input
> - series EMI filter, MOVs, etc.

Could you give examples of the EMI filters. I assume you're
talking about something that goes across the contacts of the
relay switching the AC.

> 2. EMI/spike filtering on the power supplies -
> "transient voltage suppressor" diodes [eg, Microsemi 1.5KE
> series] on the P/S input side, downstream of the AC
transformer, if there is one.

Got these.

> 3. Bypass caps, of course, at all the usual points.

Got these, too.

> 4. Of course, diodes across the relay coils and
> snubbers across relay contacts.
>    NOTE - some loads produce significantly worse switching
transients
>    than others, so the same snubber may not be universally
effective.
>    When looking across the contacts, you will see hi-speed
spikes [bad]
>    riding on a slower wave [normal] in cases where the
snubber is not
>    effective enough. You might want to use an isolation
xfrmr to do
>    this measurement.
>    NOTE - one thing you can do is sniff around with a
scope probe,
>    ungrounded, to measure presence of EMI, and determine
what it is
>    correlated to.

Got the diodes and snubbers, though obviously my snubbers
could use a redesign.

> 5. On the low-level signal lines, RC filters and transorbs
[transient
>    voltage suppressor diodes, which are essentially
low-inductance
>    zeners] are effective. Note - we ended up putting
transorbs on
>    practically ever signal line - and regular zeners are
too slow here.

I use TVS's at the power line and at the +5V input to
sensitive chips. Haven't put them on signal lines, except
for RS485 out. I was concerned with the amount of
capacitance.

> 6. Layout issues - physically separate hi/low V,
> and signal/switching circuitry. Separate power busses and
gnd
> planes [if possible]. Don't run different lines near each
other, and don't
> cross them.

This is what I was trying to accomplish by separating the
110VAC. Some of the spikes from the mag starters were
coupled back into the low V circuit either across the gap or
through the relay, which has to physically bridge that gap.
That's why I was asking about the ground plane (guard ring)
in that gap.

> 7. Use watch dog timer in uC s.w. Use debounce routines on
signal measurements.

Watch dog on the pics (2 17C44) as well as cpu supervisors
(MAX706).

> 8. Use digital bus crowbar ckt in cases where chip latchup
is an especially
>  bad problem. [Note - the watchdog will not fix latchup].

I really miswrote. The Mux does not lock up; it resets.
Since it drives the relays, all the relays will drop out
when a spike happens. Not cool. I was actually able to fix
the problem by putting bypass caps on the Chip Enable and
Clear lines of the mux. However, I would like to give myself
some wriggle room by eliminating as much of the coupled
noise as possible. Since I have to redo the board anyway, I
was trying to find other suggestions, like the guard ring.

><snip>

> Regarding hacking the test bd, try using aluminum duct
tape
> grounded back to the hiV side [looks like relay power in
this case].
> In essence, you are putting a guard ring around the hiV
side which
> is intended to contain the internal fields. Likewise, you
can
> put a gnd guard ring around each other subsystem,
connected to
> the gnd of that subsystem.

This is the main info I was looking for. Will this be as
effective for testing purposes as traces on the board? Also,
would it be better to connect this gaurd ring to earth
ground or circuit ground?

Thanks for the info.

Ryan

2000\05\24@180522 by frmiller

flavicon
face
Thanks Chris,

I do have snubbers but they need work. Do you have a good
rule of thumb for design? Most of the books and articles
that I have read really boil down to "keep trying different
values 'til it works".

Ryan


{Quote hidden}

2000\05\24@180525 by frmiller

flavicon
face
Spehro,

Could you expand on this? Is there a problem with the T90
relays?

Ryan

> Spehro Pefhany wrote:
<snip>
>
> Part of the problem is the type of relays used.

'[EE][OT] Impedance Matching a Phone Line'
2000\05\24@190231 by David Huisman

flavicon
face
John,

The phone line impedance should be 600 or 900 Ohms.

You can match to this with an opamp.

Use 47k in series with inverting input with a capacitor (where C = 1/
2*PI*47k*F, F = lowest frequency .. say 20Hz).
Now make feedback resistor = Gain Required x 47k. Say gain is 5, then
feedback resistor is 235k (use 220k or maybe a 500k pot if you want to
adjust the level).

The output of the op-amp goes to a 600 Ohm isolation transformer (Farnell
have small PCB mounting versions for Telecom) via a resistor equal to your
line impedance, the other side of the winding goes to +ve.

This now gives you a balanced, isolated drive to the line. You will need to
do a little more on the line side depending on your application (line seize
and hold circuitry etc)

Hope this is useful to you as a starting point.

Regards
David Huisman
Orbit Communications
http://www.orbitcoms.com
NSW
Australia

2000\05\24@202038 by Max Toole

picon face
In a message dated 5/24/00 2:53:21 PM Eastern Daylight Time, spam_OUTJohnCTakeThisOuTspamEraseMEININ.COM
writes:

> I am trying to connect the output of a D/A signal to an open phone line to
>  play audio (sort of similar to the "DTMF decoding with a PIC" thread that
is
{Quote hidden}

Take a look at the Motorola MC34014P speech circuit for interface to the
phone line.

Hope this helps,

Max

'Boosting power of radio modules[EE]'
2000\05\24@204116 by Dan Michaels

flavicon
face
At 07:55 AM 03/24/2000 -0000, you wrote:
.....
>Now I know the legal issues about boosting power but I am in the middle of
>no-where and I am only talking about a little power increase. The modules
....

Maybe there should be an admin heading of [FLW] - Famous Last
Words - for this kind of broadcasting <:-))). After all, with 2000
piclisters, how many do you suppose are gov't moles?? - I'd guess 30%,
from 84 different gov't agencies - US and foreign. <many G's>.

And I'm sure piclist gets scanned by "Echelon" - in case you
haven't heard of it, search on any engine.

'[EE]: 120VAC Traces'
2000\05\24@204125 by Dan Michaels

flavicon
face
Ryan Miller wrote:
....
>> 1. EMI and spike filters at the hiVAC power input
>> - series EMI filter, MOVs, etc.
>
>Could you give examples of the EMI filters. I assume you're
>talking about something that goes across the contacts of the
>relay switching the AC.
>

Actually, I was referring here to general filtering on the
power input from the AC line - which you may already have - and
which any industrial controller should have. Many commercial
versions are available, usually a C-L-L-C filter across the lines,
[C's across, L's in series in each line] with 2 C's to earth gnd,
plus MOV on downstream end, etc. Among other things, it will
help protect the controller from external noise [lightning, etc],
as  well as spikes generated by the switched loads and which are
conducted into the controller via the AC lines.
==============

{Quote hidden}

As mentioned, directly measuring the transients across the relay
contacts during on/off will help identify ineffective snubbers.
Alternatively, write some test code to exercise the relays
repetitively [at 1/sec or so] and observe which loads cause
problems. Fix those snubbers/etc. Probably use a smaller R.
================

{Quote hidden}

By "signal" lines, I really meant "all" of the low-level lines
in and out of the uC [bad terminology on my part]. It is common
for spikes to be conducted from the switched circuits directly
backwards to uC pins driving the relays. Series R's and RC's
will help here. Also, I don;t recall transorb C values, but I
believe they are small enough to not have to worry about in the
comm lines - specifically regarding the *low* V transorbs.
===============

{Quote hidden}

Here, the best defense is a good offense. First, try to kill
the spikes as dead [ie, make small] as possible. After that,
it's a systems-level, "defense" problem - ie, add preventive
measures so that spike residues have as little effect as possible.

I try to err on the conservative side, and include as many
good design features as possible, rather than just try to
get by with the minimum allowable. I think the extra cost
and effort helps in the long run. The guys I mentioned
consulting for had 10,000-20,000 units in the field and a
significant amount of "warranty" costs - about 2-5% failures
per year - that's of a lot of $$$$. By working on the
protection on the controllers over time, we were able to
greatly reduce the in-field failure rate.
=============

>> 7. Use watch dog timer in uC s.w. Use debounce routines on
>signal measurements.
>
>Watch dog on the pics (2 17C44) as well as cpu supervisors
>(MAX706).
>

Man, you already know/have it all.
===========

{Quote hidden}

Reset vs latchup is, I think, mainly related to the severity
of the garbage picked up. Your's sounds like it's on the lesser
side of real evil. The guard rings might have some small effect,
but will probably not produce magic. 1st attack the source of
the spikes - as above.
===============

{Quote hidden}

From my experiences with actually doing this, I think a good
patch of duct tape is about as effective as a real gnd plane of
the same area/etc. If adding a guard ring will have any significant
effect on the problem at all, I think it will be highly noticeable
with the duct tape jury rig.

Re ground used - try both ways & see what happens. Earth gnd might
be better. Also, it would probably help to keep the uC and relay
gnds separate if possible - if using an ULN2803 type driver or
BJTs/MOSFETs, you could run the gnds separately to the tie point.

best regards,
- Dan Michaels
==============

'[OT] [EE] Unfused printouts <-- PC board transfer'
2000\05\24@214045 by Brian Kraut

picon face
I think the problem you will have is that as soon as you try to iron it on it will
stick more to the paper than what you are trying to iron it on to.  It is also
very fragile.  A good breeze will blow the toner off and if you move it slightly
it will smudge.  The backing paper for lables works great and is cheep.

Damon Hopkins wrote:

{Quote hidden}

> > {Original Message removed}

'[EE] PC board transfer'
2000\05\24@214443 by Brian Kraut

picon face
Has anyone modified an inkjet printer to print on things like circuit boards and
front panels?

"Scott, Gary" wrote:

{Quote hidden}

2000\05\24@214903 by Dale Botkin

flavicon
face
On Sun, 14 May 2000, Brian Kraut wrote:

> Has anyone modified an inkjet printer to print on things like circuit boards and
> front panels?

Not I - my favorite was an HP pen plotter loaded with permanent ink pens,
which also make dandy etch resist.  I don't know if you can get inkjet
cartridges that print with etch-resistant ink (something not water
soluble).

Dale
---
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
               -- Isaac Asimov

2000\05\24@215920 by Mark Willis

flavicon
face
The problem (as I see it) is that many inkjets (all that I own, for
certain!) have water-soluble ink;  I could print with an InkJet then
photocopy onto glossy paper then fuse THAT onto a PCB, but it doesn't
make a lot of sense to put water-soluble ink down as etch "resist" then
dunk in Ferric Chloride.  (Not pretty when I print onto an envelope then
walk it out to the mailbox in the rain, either.)

The other problem I see with inkjets is that their ink's nowhere near as
"thick" and opaque, as laser printer toner.  So would have to mess with
contrast a little when photocopying.

So, even if you made one to go with a straight media path, still have
problems - Laser's go for $25 occasionally around here used, was given
one free the other day, so I'll stick with laser printers.

 Mark

Brian Kraut wrote:
{Quote hidden}

'Boosting power of radio modules[EE]'
2000\05\24@223105 by Don

flavicon
face
On 24 Mar 2000, at 7:55, Andrew Seddon wrote:

> I have purchased a couple of radio transceiver modules from
> http://www.radiometrix.com however the rated output power is a tad on the low
> side. Now I know the legal issues about boosting power but I am in the
> middle of no-where and I am only talking about a little power
> increase. The modules work at 433.92Mhz and output 6dbm(is that a good
> measure of power? I have no RF experience). They are half duplex and
> the TX/RX works off the same antenna. I was wondering if it would be
> possible to maybe place a transistor and a resistor in place of the
> antenna to boost the power.
>
> Any help appreciated.
>

You can certainly make an amplifier, but if you havent worked with
rf circuits, it will take you a while to get the knack. You might want
to buy an amateur radio handbook and read some of the material,
and maybe experiment some. You will also need to buy or build
some basic RF test equipment, and again, the handbook can help.
One thing to keep in mind is the nature of UHF transmissions. It is
almost line of sight, like light, so if you are down in a valley, you
might have a very large power and still not be able to tranmit as far
as a few mw on a hill top. If you are looking for range in a particular
direction, you might get improvement by building an antenna with
higher gain, and/or paying attention to the matching of the output
stage and the antenna. Again, the handbook can help here. Be
sure you don't cause interferrence....sometimes, repeaters are also
put in some pretty out of the way places.
Oh, your 6dbm figure means the output power is 6 decibels above
a milliwatt.

2000\05\24@224803 by Gennette, Bruce

flavicon
face
Rather than go illegally over-power in the transmitters you can boost the
receivers with a MAR6 and a couple of caps for a few of dollars.  (good
stipline construction with the MAR6 sitting in a hole in the board IS
required).

Bye.

       {Original Message removed}

'[EE]: Impedance Matching a Phone Line'
2000\05\24@225848 by Clark, John

flavicon
face
MC34014P

Looks interesting from the few application notes I found, but for whatever
reason I cannot seem to find data sheets on this product...  Could you give
me a direct link?  This looks like it may be worth investigating.

Additionally, is there additional certifications needed for telco
connectivity?  A complete third party product that could save us additional
certifications may be an attractive alternative (depending on unit price).


John Clark
Indianapolis, IN

{Original Message removed}

'[EE]: 120VAC Traces'
2000\05\24@232821 by Robert A. LaBudde

flavicon
face
<x-flowed>At 02:58 PM 5/24/00 -0700, ryan wrote:
>Thanks Chris,
>
>I do have snubbers but they need work. Do you have a good
>rule of thumb for design? Most of the books and articles
>that I have read really boil down to "keep trying different
>values 'til it works".

Typical values are 0.1 uF with series 100 ohm.

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: .....ralRemoveMEspamlcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causas scire"
================================================================

</x-flowed>

'Boosting power of radio modules[EE]'
2000\05\25@003828 by paulb

flavicon
face
Quitt, Walter wrote:

> 433 is close enough to the ham bands that you should be able to get
> one for amateur radio use that will do real well.

 In this country at least, 433 *IS* an amateur band - which is why they
(we) aren't too pleased about the proliferation of these devices.  In
effect, it's an ISM band.

 *Presuming* the modules have a poor input noise figure, a low NF
*tuned* amplifier, quite possibly using a MAR-6, better a GaAsFET, would
help.

 There is no regulation on receiver gain in this application (unless
perhaps it's a transceiver module), so by all means use a yagi, array
or dish on the receiver.  (Dishes are made of chickenwire).
--
 Cheers,
       Paul B.

2000\05\25@024340 by mike

flavicon
picon face
AFIK its right in the middle of the 70cms ham band in UK.
a web search for 70cms pre-amp should find something. Failing
that the " remote imaging group " may have something.
But did'nt he say it was a BIM tranciever?, in that case it may be
difficult to get into the RX path. I'd personally go for a beam
antennae, with the module at the feedpoint to reduce feeder losses,
if directionality is acceptable.

On 25 May 00, at 0:09, Automatic digest processor wrote:

{Quote hidden}

--
Life is dark and empty for the PIC developer without VirtualBreadboard
go look at it...  http://www.virtualbreadboard.com

'[EE]: Impedance Matching a Phone Line'
2000\05\25@031155 by Brian Hopkins

flavicon
face
John,
It seems what you are looking for is a pre-certified DAA...and ideally
certification that is transferable to your product.
The certifications your are concerned about for North America are FCC Part
68 (USA) and DOT CSA CS-03 Part I (Canada)
Try XECOM
http://www.xecom.com/_PageFiles/about.htm
or Cermetek
http://www.cermetek.com/

Hope this helps
Brian
{Original Message removed}

'[EE] PC board transfer'
2000\05\25@040524 by Alan B Pearce

face picon face
>Has anyone modified an inkjet printer to print on things like circuit boards
and
>front panels?

I have seen people suggest using special pens in flat bed plotters, but I think
you will have a problem with an inkjet printer, as all the inks they use are
water soluble AFAIK.

2000\05\25@090343 by Albert Noah

flavicon
face
Actually, you can get indelible inks to refill your cartridges with. I had
to do this to print labels for packaging in a freezer. Worked great where as
the normal inkjet ink just ran and smeared. I got the ink from a company
called V-Tech.

Hope this helps,

Albert

{Original Message removed}

'Boosting power of radio modules[EE]'
2000\05\25@091350 by Andrew Seddon

picon face
----- Original Message -----
From: Dan Michaels <TakeThisOuToricomspamspam_OUTLYNX.SNI.NET>
To: <RemoveMEPICLISTspamspamSTOPspamMITVMA.MIT.EDU>
Sent: Thursday, May 25, 2000 12:40 AM
Subject: Re: Boosting power of radio modules[EE]


> At 07:55 AM 03/24/2000 -0000, you wrote:
> .....
> >Now I know the legal issues about boosting power but I am in the middle
of
{Quote hidden}

Thanks for the tips but I`m not going in to hiding just yet :-). The modules
will be placed on a farm. The nearest house is about 1.5-2km away. They are
currently rated at 200m open ground and I was looking for around 400-500m.

'[EE]: 120VAC Traces'
2000\05\25@103413 by Dan Michaels

flavicon
face
Robert wrote:
>At 02:58 PM 5/24/00 -0700, ryan wrote:
>>Thanks Chris,
>>
>>I do have snubbers but they need work. Do you have a good
>>rule of thumb for design? Most of the books and articles
>>that I have read really boil down to "keep trying different
>>values 'til it works".
>
>Typical values are 0.1 uF with series 100 ohm.
>

And you probably realize it, but there are *special*
capacitors made particularly for this type of application.
They tend to be rather bulky and take up a lot of board
space. Not any old cap will do.

'Boosting power of radio modules[EE]'
2000\05\25@111726 by mike

flavicon
face
On Fri, 24 Mar 2000 22:12:37 -0000, you wrote:

{Quote hidden}

If the link is fixed, I'd try directional antennas like Yagis first.
This will also reduce the chance of interference (to or from your
system).
Modules are available for other bands (I think theres one around
900MHz) that can legally operate at higher power levels.

2000\05\25@135522 by Ian Wilkinson

flavicon
face
On Thu, 25 May 2000 in "Re: Boosting power of radio modules[EE]", Paul B. Webster VK2BZC wrote:
>Quitt, Walter wrote:
>
>> 433 is close enough to the ham bands that you should be able to get
>> one for amateur radio use that will do real well.
>
>  In this country at least, 433 *IS* an amateur band - which is why they
>(we) aren't too pleased about the proliferation of these devices.  In
>effect, it's an ISM band.

In this country 433 Was an entire amateur band,  We now have a 2 MHz chunk taken
out of the 70cm band for these devices...  Some did say we benefitted, we now
have two 70cm's bands...

Check out amateur radio information.  These modules tend not to filter out
interference very well so you could look into filters and Amps on the Rx side
as well as high gain aerials...

If there are restrictions on aerials have some way of switching to a lower gain
aerial before Transmitting and then back to the high gain when receiving...

Ian
--
Medical Record quotations:
The skin was moist and dry.

Uptime at  8:18am  up 10 days, 10:09,  8 users,

2000\05\25@142920 by David VanHorn

flavicon
face
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1


>Thanks for the tips but I`m not going in to hiding just yet :-). The modules
>will be placed on a farm. The nearest house is about 1.5-2km away. They are
>currently rated at 200m open ground and I was looking for around 400-500m.

So you'll need 6-8dB antenna gain.
A five element yagi on the receiver, pointed at the transmitter, will do
this, and is perfectly legal.  Also, you'll probably find that they
out-perform their specified range in this quiet environment.

Look in an ARRL antenna book, under UHF antennas.

- --
Are you an ISP?  Tired of spam?
http://www.spamwhack.com  A pre-emptive strike against spam!

Where's Dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9

-----BEGIN PGP SIGNATURE-----
Version: PGPfreeware 6.5.2 for non-commercial use <http://www.pgp.com>

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=DMt5
-----END PGP SIGNATURE-----

2000\05\25@161637 by l.allen

picon face
David Wrote
>
> So you'll need 6-8dB antenna gain.
> A five element yagi on the receiver, pointed at the transmitter, will do
> this, and is perfectly legal.  Also, you'll probably find that they
> out-perform their specified range in this quiet environment.
>
> Look in an ARRL antenna book, under UHF antennas.
>
> - --
A Yagi antenna will be directional (stating the blinding
obvious) and therefore focuses power in one direction,
and since Andrew said the unit  presently used one aerial
for both Tx and Rx then a 20 to 40dB gain that some
Yagis can yield will put the field strength (in the beam)
through the roof... being up to 10,000 times more intense
than isotopic.
But as David said... good if you attach only to the Rx and
are happy with a focused path (like from building to
building).


_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

http://www.psych.auckland.ac.nz

_____________________________

'[EE]: Re: Step up voltage regulator'
2000\05\25@171526 by Roland Andrag

flavicon
face
There are various voltage doubler chips available.  I think (one of) the
original chip(so) was the ICL7660, now also available from many other
manufacturers e.g.. MAX7660 from Maxim. To volunteer the info that launched
me into electronics properly: If you ever feel like buying a book that
contains this and a thousand other useful pages of info get 'The Art of
Electronics', by Horowitz and Hill. You won't regret it.

Roland



----- Original Message -----
From: Soon Lee <.....pslnEraseMEspamCYBERWAY.COM.SG>
To: <spamPICLISTspam_OUTspam@spam@MITVMA.MIT.EDU>
Sent: Thursday, May 25, 2000 7:53 AM
Subject: Step up voltage regulator


Hi All

Do anyone have any idea in how to step up voltage
like from 5 volts to 10volt
Is there such things call step up regulators?
if there are may i know the part number thanks
i heard that there is one of such device in picstart that step a 9V to 13 V
any oneknow the part number thanks

'Boosting power of radio modules[EE]'
2000\05\25@173647 by David VanHorn

flavicon
face
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1


>for both Tx and Rx then a 20 to 40dB gain that some
>Yagis can yield will put the field strength (in the beam)
>through the roof... being up to 10,000 times more intense
>than isotopic.

40dB is going to take a pretty expensive antenna.
6-8 is cheap, and probably all he needs.

- --
Are you an ISP?  Tired of spam?
http://www.spamwhack.com  A pre-emptive strike against spam!

Where's Dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9

-----BEGIN PGP SIGNATURE-----
Version: PGPfreeware 6.5.2 for non-commercial use <http://www.pgp.com>

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=EUJl
-----END PGP SIGNATURE-----

'[EE]: 120VAC Traces'
2000\05\26@063333 by Tom Handley

picon face
At 11:18 AM 5/24/00 -0600, Dan Michaels wrote:
>BTW, a good book on this topic is
>
>"Noise Reduction in Electronic Systems" by Henry Ott

  Dan, I also have this book and highly recommend it. For those interested:

     Noise Reduction Techniques in Electronic Systems
     Henry W. Ott
     Wiley-Interscience
     ISBN: 0-471-65726-3

  Another good one is:

     Low-Noise Electronic Design
     C.D. Motchenbacher and F.C. Fitchen
     Wiley-Interscience
     ISBN: 0-471-61950-7

  - Tom


------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

'Boosting power of radio modules[EE]'
2000\05\26@065657 by Andrew Seddon

picon face
Thanks for all the help on this. I have decided to get myself a decent
antenna on one end of the link. For reasons of portability one end has to
use a crappy wip. The only question I have is how directional is a yagi?? I
wan`t an angle of acceptane of about 30 degrees on the horizontal and about
5 on the vertical.

Thanks.

'[EE]: Boosting power of radio modules/Yagi beamwi'
2000\05\26@091349 by Jim P

flavicon
face
Taking a quick look at the Decibel Products catalog
for a 6-element 10 dBd gain UHF band Yagi (-"Uda")
antenna such as the DB436 through DB438 Yagis:

Horz. Beamwidth:  60 deg. (3 dB points)
Vert.  Beamwidth:  44 deg. (3 dB points)

This assumes vertical orientation of the E-plane (elements
placed vertically).

To achieve a substantially tighter vertical pattern (you
mentioned 5 deg. vert. as a 'spec') Yagis can be stacked
vertically to tighten up this pattern while increasing gain
and not affecting the horrizontal pattern.

Two Yagis of the type above would 13 dBd gain, 4 stacked
Yagis would yield 16 dBd ...

Jim P

{Original Message removed}

'[EE]: Re: Step up voltage regulator'
2000\05\26@112756 by Dan Mulally

flavicon
face
A note on the 7660. It does not provide regulation so consider your current
draw to see if the voltage drop is acceptable.

Dan

{Original Message removed}

'[EE] TDA 8822 video modulator'
2000\05\26@123030 by Dan Mulally

flavicon
face
Has anyone used the Philips TDA 8822 video modulator? I'm  trying to set it
with the I2C buss and am having trouble. It seems to be getting some data
because it's operation changes when I load data but I can't get the test
modes or nomal modes to work properly. The P0 port always has a 7.813kHz
signal present (fref/512), I don't get any RF out but the VCO seems to be
working but not locking. My configuration bytes now are: CA, 44, 34, A2, E4.
Any help would be appreciated. Thank you in advance.

Dan Mulally

spamdtcon@spam@spamSTOPspamrapidnet.com
http://rapidnet.com/~dt2000

'[EE] Re: Boosting power of radio modules[EE]'
2000\05\26@123625 by Dan Mulally

flavicon
face
Mini circuits have several easy to use amplifiers that can boost the output
to up to 30dBm (1Watt) depending on if linearity is desired. Your system is
probably FM so linearity is not needed or desired since linear amps are
inefficient. You need to check the FCC rules.

Dan Mulally

{Original Message removed}

'[EE] Microcontroller with 4 USARTs and 40 pins'
2000\05\26@130144 by Edson Brusque

face
flavicon
face
Hello,

   someone knows if there's a microcontroller with 4 USARTs capable of
working at 31250bps? I need extra 24 I/Os minimum. One USB port would be a
plus. Also, I would need an A/D converter, but I could use an external one.

   Maybe a SCENIX can do 4 USARTs as virtual peripherals???

   Best regards,

   Brusque

2000\05\26@134517 by Chris Eddy

flavicon
face
Edson, I think that you want to check out the Rabbit 2000.  I have seen it
advertised in the likes of Circuit Cellar.

Chris Eddy

Edson Brusque wrote:

{Quote hidden}

'[EE] Re: Boosting power of radio modules[EE]'
2000\05\26@135344 by Harold M Hallikainen

picon face
On Fri, 26 May 2000 10:24:59 -0600 Dan Mulally <spamBeGonedtconspamBeGonespam@spam@RAPIDNET.COM>
writes:
> Mini circuits have several easy to use amplifiers that can boost the
> output
> to up to 30dBm (1Watt) depending on if linearity is desired. Your
> system is
> probably FM so linearity is not needed or desired since linear amps
> are
> inefficient. You need to check the FCC rules.
>

       Assuming you are operating this as an FCC part 15 unlicensed intentional
radiator (and not some licensed transmitter, such as amateur), the
appropriate rules are in part 15.
       FCC Rules regarding unlicensed intetional radiators start at section
15.201. The table of contents with links to rules is available at
http://hallikainen.com/cgi-bin/section.pl?section=15 .
       In particular, note that 15.201requires such devices to be
"certificated" with the Commission. Adding power amplifiers, etc. would
violate this certification (the equipment is not the same that was
certificated).
       See also 15.204 which prohibits use of an antenna other than that
supplied with the transmitter on a part 15 intentional radiator.

Harold


FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk!  For your FREE software, visit:
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'[EE] Microcontroller with 4 USARTs and 40 pins'
2000\05\26@141039 by M. Adam Davis

flavicon
face
Perhaps if you give us a little more information we can help you out more.  If
you take an atmel or scenix micro you could fairly easily develop 4 software
UARTs if they are all running at the same speed.  The PIC probably wouldn't run
fast enough unless you are doing very little or no processing of the data.  (I
just mashed a 4800bps full-duplex software UART into a 16c54 running at 4MHz
with a small bit of data processing...  It took a /lot/ of planning...)

It is unlikely that you will find an 8-bit micro with 4 hardware UARTs (as a
hobbyist), so you probably should plan on finding one with one or two UARTs and
build the rest in software.  If I were in your shoes, I would build them all in
software.  If you run a scenix or atmel at 24 MIPs, you'll have exactly 768
instructions (scenix, varies for atmel) per bit time to run the UARTs and your
user process (at the specified 31.25Kbps).  Divide it by four (bit slicing) and
you end up with 192 instructions to read the state of four RX lines, change the
state of four TX lines, and then do some data processing.  It really would not
be too difficult.

-Adam

Edson Brusque wrote:
{Quote hidden}

2000\05\26@142939 by Dan Michaels

flavicon
face
Edson Brusque wrote:
.....
>>     someone knows if there's a microcontroller with 4 USARTs capable of
>> working at 31250bps? I need extra 24 I/Os minimum. One USB port would be a
>> plus. Also, I would need an A/D converter, but I could use an external one.
>>
>>     Maybe a SCENIX can do 4 USARTs as virtual peripherals???
>>

Scenix can easily do this, **BUT** you will have to go to 48 or
52-pin PQFP part - with tiny smt pads - to get 24 additional I/O lines.
No PLCC available. [or possibly do a multiprocessor with 18 & 28
pin parts - not all that hard to build off a single RS-232 host line].

And I suspect with the scenix, you actually could get the weird
31250 rate you indicate here - or any other weird baudrate imaginable.
But whatcha gonna talk to at that speed?
================

Adam Davis wrote:
>Perhaps if you give us a little more information we can help you out more.  If
>you take an atmel or scenix micro you could fairly easily develop 4 software
>UARTs if they are all running at the same speed.  The PIC probably wouldn't run
..........

I believe with the scenix VP route, the separate UARTs do *not* have
to be running at the same bps. The VPs all run off the same basic
timer interrupt, but each uses a different divider to index its
update rate.

cheers,
- Dan Michaels
Oricom Technologies
===================

'[EE] Re: Boosting power of radio modules[EE]'
2000\05\26@144015 by Dan Michaels

flavicon
face
Harold wrote:
.....
>        Assuming you are operating this as an FCC part 15 unlicensed
intentional
{Quote hidden}

....


If I read this correctly, Harold, you are saying that even an
"unlicensed" transmitter still "must" be certified.

<SECRET STUFF>
Shoot - in for a penny, in for a pound. I guess if someone does
this the "wrong" way, they might as well go "all the way" - and
break all the rules - overpowered, illegal antenna, non-certified,
what the heck. [did all you Echelon moles pick this up?].

Maybe we should have an [ECHELON] admin category to make
Echelon's job easier!!
</SECRET STUFF>

'[EE] Microcontroller with 4 USARTs and 40 pins'
2000\05\26@151309 by Andrew Seddon

picon face
There is a VP on the scenix site with I think 8 USART`s running not sure of
the speed but I know it is on a 50mhz SX28. If you were to get a new 100mhz
SX52/48 I am sure you could do pretty much everything in software, not sure
about the USB.

> Hello,
>
>     someone knows if there's a microcontroller with 4 USARTs capable of
> working at 31250bps? I need extra 24 I/Os minimum. One USB port would be a
> plus. Also, I would need an A/D converter, but I could use an external
one.
>
>     Maybe a SCENIX can do 4 USARTs as virtual peripherals???
>
>     Best regards,
>
>     Brusque
>

'[EE] Re: Boosting power of radio modules[EE]'
2000\05\26@153824 by Andrew Seddon

picon face
I don`t think most of this applies to me as I am in the UK. Believe me if I
thought there was any chance of causing disruption to others I wouldn't`t
even consider it. I know the band I am transmitting on is set aside for
short range keyfob transmitters etc. BTW it is actually 418Mhz I am
transmitting on not 433 as I previously said.

> Harold wrote:
> .....
> >        Assuming you are operating this as an FCC part 15 unlicensed
> intentional
> >radiator (and not some licensed transmitter, such as amateur), the
> >appropriate rules are in part 15.
> >        FCC Rules regarding unlicensed intetional radiators start at
section
{Quote hidden}

'[EE] Microcontroller with 4 USARTs and 40 pins'
2000\05\26@161428 by Harold M Hallikainen

picon face
       Another approach is to use Maxim external uarts hung on a serial bus out
of the PIC.

Harold


FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk!  For your FREE software, visit:
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'[EE] Re: Boosting power of radio modules[EE]'
2000\05\26@161439 by Harold M Hallikainen

picon face
On Fri, 26 May 2000 12:38:23 -0600 Dan Michaels <RemoveMEoricomRemoveMEspamRemoveMELYNX.SNI.NET>
writes:
{Quote hidden}

       Yes, 15.201 pretty much requires that. However, 15.23 allows "home built
devices" as follows...

Sec. 15.23  Home-built devices.

   (a) Equipment authorization is not required for devices that are not
marketed, are not constructed from a kit, and are built in quantities of
five or less for personal use.
   (b) It is recognized that the individual builder of home-built
equipment may not possess the means to perform the measurements for
determining compliance with the regulations. In this case, the builder
is expected to employ good engineering practices to meet the specified
technical standards to the greatest extent practicable. The provisions
of Sec. 15.5 apply to this equipment.



       I don't believe that adding an unauthorized power amplifier or antenna
to a commercial device would make the resulting system "home built." I
believe that this section continues to require that users of home built
equipment comply with all the limits of part 15, but recognizes that a
typical person does not have the means to make the required measurements.


Harold



FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk!  For your FREE software, visit:
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2000\05\26@161442 by Harold M Hallikainen

picon face
       Actually, I'd expect NONE of the US FCC rules to apply in the UK.
However, most countries have very similar rules on unlicensed
transmitters.

Harold


On Fri, 26 May 2000 08:34:23 +0100 Andrew Seddon <seddonaKILLspamspamspamHOTMAIL.COM>
writes:
{Quote hidden}

FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk!  For your FREE software, visit:
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'[EE]: Re: About serial port scoping'
2000\05\26@163122 by mike

flavicon
picon face
DataScope is a powerful serial communications analyzer
designed as a high performance tool for software and
hardware professionals. Now you can eliminate guesswork
about asynchronous transmissions, connections, character
timing, and serial events without purchasing an expensive
hardware monitor.

I did'nt write the description ;-) and  its only 90k long.

www.simtel.net/pub/simtelnet/msdos/sysutl/scope140.zip
http://www.corn2.freeserve.co.uk/scope140.zip  *** only for a few
days ***


ATB  Mike W

On 25 May 00, at 7:42, pic microcontroller discussio wrote:

> IIRC there was a program from Simtel Archives called DSCOPE
> that achieved this. I might still have it on my tape archive. IF I can
> still read it (big IF) and if anyones interested.
>
> Could this be a project for the PIC testbench mentioned last year?.
>
> Mike W

--
spam_OUTmike@spam@spamcorn2.freeserve.co.uk

Never underestimate the power of Human stupidity

'Boosting power of radio modules[EE]'
2000\05\26@171117 by Andrew Seddon

picon face
Yeh that`s what I was getting at. What I mean is that I would imagine
noise/power specs etc to be similar for similar devices.

>         Actually, I'd expect NONE of the US FCC rules to apply in the UK.
> However, most countries have very similar rules on unlicensed
> transmitters.
>
> Harold
>
>

'[EE]Re: TCP/IP SEIKO STARTER KIT (USING THE PARALL'
2000\05\26@171532 by Andrew Seddon

picon face
> No, i have the Specctra Autoroute 7.1, i did pay for it U$1245,00
>
> Miguel
>

Really how do you find it?? Not that I can really get it on a students
budget. I am currently working through every computer I can find with the 30
day trial on Protel. I have to say my experience is limited but I managed to
layout a pretty complex board and I didn`t find it too much trouble. Also
the autorouter does about a good a job as I think I could do.

'[EE] Microcontroller with 4 USARTs and 40 pins'
2000\05\26@182255 by Edson Brusque

face
flavicon
face
> Perhaps if you give us a little more information we can help you out more.

   As I'm a musician, and my (piano) keyboard controller doesn't makes all
the tricks I would like it to do, I'm thinking in developing a MIDI
black-box that could do everything I want. Maybe I can sell hundreds of
units and make some money :)

> It is unlikely that you will find an 8-bit micro with 4 hardware UARTs (as
a
> hobbyist), so you probably should plan on finding one with one or two
UARTs and
> build the rest in software.  If I were in your shoes, I would build them
all in
> software.  If you run a scenix or atmel at 24 MIPs, you'll have exactly
768
> instructions (scenix, varies for atmel) per bit time to run the UARTs and
your
> user process (at the specified 31.25Kbps).  Divide it by four (bit
slicing) and
> you end up with 192 instructions to read the state of four RX lines,
change the
> state of four TX lines, and then do some data processing.  It really would
not
> be too difficult.

   I think I'll want to put 16 keys on the thing (8 I/Os for that), an LCD
(6 I/Os for that), four MIDI Ins plus four midi Outs (8 I/Os), and I would
like it to communicate with the PC with Paralell or USB. Even Serial at
115.200bps would do the job nicely. Well, this puts 22 I/Os plus PC
communication. A 48 or 52 pin Scenix at 50MHz seens to be a very good option
(I've took a look at SX documentation and it says it can run eight 19.2Kbps
UARTs using 13% of 50MHz). The hard thing will be to make an adaptor to use
it on a proto-board.

   I would also like to put 16 pots on it to control various things (like
volume, pan, reverb, modulation, etc).

   I would preffer to make it with PICs, but I don't think it's possible. I
don't want to expend money on another C compiler, debugger, etc...

   Atmel would also be a good option. What Atmel micros can do 24MIPS?

   Best regards,

   Brusque

2000\05\26@190523 by Andrew Seddon

picon face
>     I would preffer to make it with PICs, but I don't think it's possible.
I
> don't want to expend money on another C compiler, debugger, etc...

Try http://www.geocities.com/SiliconValley/Network/3656/c2c/c.html for a C
and Pascal compiler that will work with the 52/48. Also if you talk to Mr
Newton I am sure he will sort you out with a demo board and socket, I would
send you the layout for mine but it is pretty crappy in comparison.

2000\05\26@191144 by Edson Brusque

face
flavicon
face
Hello Dan,

> Scenix can easily do this, **BUT** you will have to go to 48 or
> 52-pin PQFP part - with tiny smt pads - to get 24 additional I/O lines.
> No PLCC available. [or possibly do a multiprocessor with 18 & 28
> pin parts - not all that hard to build off a single RS-232 host line].
>
> And I suspect with the scenix, you actually could get the weird
> 31250 rate you indicate here - or any other weird baudrate imaginable.
> But whatcha gonna talk to at that speed?

   31250bps isn't weird: 1,000,000 (instructions for second) / 31250 (bps)
= 32 (instructions for serial bit).

   I'm looking at an Atmel datasheet. It says the AT89C55 can do 33MHz, but
how much clocks does it takes to execute one instruction? Why few
manufacturers put this information on the datasheets??? 33Mhz equals to
33MIPS? Or 8,25MPIS? Or 2,75 MIPS???

   Regards,

   Brusque

'[PIC]: [EE]: Microcontroller with 4 USARTs and 40 '
2000\05\26@232352 by Bob Ammerman

picon face
Does the application require 4  _bi_directional UARTs? Or can some of your
MIDI ports be unidirectional (ie: how many MIDI ins and MIDI outs do you
need).  Bit banging the transmit side is _much_ easier than the receive
side. You could set up an interrupt source at the bit rate (31250) and
easily have time to blast out the bits. I would suggest, perhaps, the 18C
series chips, running at a 10MHz crystal, with the PLL x4 to get 10MIPS.
This would give you 320 instructions per bit time, which is nearly
'forever'.

Unfortunately, to receive you need to run your interrupt handler somewhat
faster than the bit time.  I have successfully built a software UART using a
interrupt 6x of the bit rate. I expect 5x would work pretty well.

So, you would have to take 1 interrupt every 64 instruction times. I'm
guessing about a 8 instruction time overhead in the interrupt handler (the
18C can be quite efficient at this) and perhaps 15 instructions per
interrupt per receiver. You could handle 5 transmitters by processing them
round-robin, one per interrupt (say another 10 instructions).

Thus, our interrupt budget would be about 8 (overhead) + 15*Number of
receivers + 10 instructions.

Assuming 2 receivers, this would take about 48 instructions, leaving you
with about 2.5 MIPS for 'task-level' code.

I really think this could be done on the 18C chips!

BTW: I have developed an 18C application that directly generates (no
hardware other than the PIC and 3 resistors) a full-screen animated NTSC
(monochrome) image -- this chip can really make things happen!

Bob Ammerman
RAm Systems
(high function, high performance, low-level software)

'[EE]: Re: About serial port scoping'
2000\05\27@014831 by Robert Rolf

picon face
See also

http://www.fte.com/

SerialTest Spy. A windows comm port shim that taps the data going to
and from a serial port. You don't need a separate PC since it
creates a software T connection. Very good software, but you have
to pay the registration fee to get it log more than a couple of kB.

More on Dscope below:

Mike W wrote:
{Quote hidden}

www.ultranet.com/~dtweed/cajindex/ftp_area/areaib41.htm
ftp://ftp.circuitcellar.com/IBMPC/OTHER/DSCOPE.ZIP

> >
> > Could this be a project for the PIC testbench mentioned last year?.
> >
> > Mike W
>
> --
> TakeThisOuTmikespam_OUTspamcorn2.freeserve.co.uk
>
> Never underestimate the power of Human stupidity

'[EE] Non interacting zero and span. how?'
2000\05\27@021421 by Dan Mulally

flavicon
face
----- Original Message -----
From: "Chris Eddy" <KILLspamceddy.....spamTakeThisOuTNB.NET>
To: <TakeThisOuTPICLISTEraseMEspamRemoveMEMITVMA.MIT.EDU>
Sent: Saturday, May 20, 2000 5:22 PM
Subject: [EE] Non interacting zero and span. how?


{Quote hidden}

You could use an inverting summing configuration with a fixed resistor in
the feedback loop and 2 rheostats connected to the inverting input. One
rheostat can connect to a DC source and the other to your signal. The output
will be inverted so you may have to use another opamp invertor to get the
correct polarity.

Dan Mulally

'[EE] Re: Boosting power of radio modules[EE]'
2000\05\27@072730 by mike

flavicon
picon face
On 27 May 00, at 0:01, Automatic digest processor wrote:

> Date:    Fri, 26 May 2000 10:51:04 -0700
> From:    Harold M Hallikainen <spam_OUTharoldhallikainenRemoveMEspam.....JUNO.COM>
> Subject: Re: [EE] Re:      Boosting power of radio modules[EE]
>
<<snip>>
>
>         Assuming you are operating this as an FCC part 15 unlicensed
> intentional
> radiator (and not some licensed transmitter, such as amateur), the
> appropriate rules are in part 15.
<< 'nother snip>>
>         See also 15.204 which prohibits use of an antenna other than
> that
> supplied with the transmitter on a part 15 intentional radiator.
>
> Harold
>
how do you do a smiley blowing a friendly rasberry?.

'Boosting power of radio modules[EE]'
2000\05\27@072735 by mike

flavicon
picon face
Andrew, where are you in the world?. sometimes UHF band A TV
antennae can be used straight from the box.  If I were you i'd go for
minimum acceptable gain in the antennae, this coincides with
wider apatures, for a gain of 6dbd your beamwidth should be plenty
wide. Try looking in the ARRL ( amateur radio relay league. US
based) handbook or the RSGB ( radio society of great britain. UK
based !) handbook for specific data on gain vs apature. e-mail me if
you wish for a simple design to make yourself.. Mike W

On 27 May 00, at 0:01, Automatic digest processor wrote:

{Quote hidden}

'[EE]Re: TCP/IP SEIKO STARTER KIT (USING THE PARALL'
2000\05\27@110532 by WF

flavicon
face
I got it in IVEX in 1998

My board aren't complex...during 7 year i did use the MANUAL OPTION route of
Tango...

When you have a complex layout for route, you have to change the RULES of
routing...othewise, can not route 100%...

My specctra is limited for 4000 holes and 2 layes, but is enough for me...

Miguel

{Original Message removed}

'[EE] Microcontroller with 4 USARTs and 40 pins'
2000\05\27@115818 by Dan Michaels

flavicon
face
Edson wrote:
.........
>> And I suspect with the scenix, you actually could get the weird
>> 31250 rate you indicate here - or any other weird baudrate imaginable.
>> But whatcha gonna talk to at that speed?
>
>    31250bps isn't weird: 1,000,000 (instructions for second) / 31250 (bps)
>= 32 (instructions for serial bit).
>

Only weird viz-a-viz the "usual" baudrates, like 19200, 38400, 57600,
etc. For local networks, anything is a go. But I'm not sure whether
a PC, if used as a host, could accommodate anything like 31250. Depends
upon the internal clocks and USART h.w.

The scenix s.w. VP could probably be massaged to accommodate both 31250
and 38400, for example, if you try hard enough. 50Mhz/38400 = 1302 and
50Mhz/31250 = 1600.

- Dan

2000\05\27@163855 by Sebastian Garcia

flavicon
face
Edson wrote:

| I'm looking at an Atmel datasheet. It says the AT89C55 can do 33MHz,but
|how much clocks does it takes to execute one instruction? Why few
|manufacturers put this information on the datasheets??? 33Mhz equals to
|33MIPS? Or 8,25MPIS? Or 2,75 MIPS???


If it don't say anything more, it may be the classic 8051's: one machine
cycle is formed by twuelve clock cycles, and the instruction cycle
depends on the particular instruction.


If You want more speed enhacement look at Dallas MCS-51 compatible, hi-speed
micros.

Regards,

S.-

2000\05\27@180739 by David VanHorn

flavicon
face
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1


>If it don't say anything more, it may be the classic 8051's: one machine
>cycle is formed by twuelve clock cycles, and the instruction cycle
>depends on the particular instruction.
>
>
>If You want more speed enhacement look at Dallas MCS-51 compatible, hi-speed
>micros.


Or the AVR, at one xtal clock per instruction (a few take two). 8 mhz, but
that's 96 to an 8051 apparently.

- --
Are you an ISP?  Tired of spam?
http://www.spamwhack.com  A pre-emptive strike against spam!

Where's Dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9

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Version: PGPfreeware 6.5.2 for non-commercial use <http://www.pgp.com>

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ZPWtc4N49sDH1YL4AotBu6qG
=Osxj
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'[EE]Re: TCP/IP SEIKO STARTER KIT (USING THE PARALL'
2000\05\28@031522 by Damon Hopkins

flavicon
face
Andrew Seddon wrote:
>
> > No, i have the Specctra Autoroute 7.1, i did pay for it U$1245,00
> >
> > Miguel
> >
>
> Really how do you find it?? Not that I can really get it on a students
> budget. I am currently working through every computer I can find with the 30
> day trial on Protel. I have to say my experience is limited but I managed to
> layout a pretty complex board and I didn`t find it too much trouble. Also
> the autorouter does about a good a job as I think I could do.

http://mainstream.pcb.cadence.com/specctra/index.asp

'[EE] Flash and EEPROM based file systems'
2000\05\28@041657 by Damon Hopkins

flavicon
face
anyone have any code dealing with implementing a file system on either
FLASH memory or any other type of memory.. I'd like to get a 1 MB flash
chip and put a small filesystem on it but rather than try to design the
thing myself I'd like to sample what's out there.. I haven't turned up
much. I plan on using the Atmel SPI Flash memory chips and figure that
with a 16 bit pointer I could have access to 4 MB I want to make a tiny
file server :)

                       Thanks,

                                       Damon Hopkins

'[EE] Info: Rechargeable Lithium coin cells'
2000\05\28@070258 by Russell McMahon

picon face
I went looking for info on rechargeable Lithium coin cells and found it very
hard to find anything technical.
Here's the best of my slim pickings.

Most of following sites are subset of this one with good source of battery
technical data including tables etc
       http://www.allbatteries.com

Sanyo ML series rechargeable Lithium Manganese coin cells
   http://www.allbatteries.com/sanyo19.htm

Varta MC series Lithium Ion coin cells
   http://www.allbatteries.com/vartrlbc.htm

Varta also do button cells in NiMH which have a much higher max
charge/discharge rate.
   http://www.allbatteries.com/nimhre24.htm

Maxell make them too (and sell them via eg Farnell 3031998 etc) but don't
seem to want to tell you about them on their various sites.
A bit at
   http://www.maxell.co.jp/eng/device/ml_bat/


Std Lithium coin cells - discharge curves. usefulish
   http://www.tbcl.co.jp/TB_e/lb_b_e.htm

`

'[PIC]: [EE]: Microcontroller with 4 USARTs'
2000\05\28@070501 by Alan B Pearce

face picon face
>Unfortunately, to receive you need to run your interrupt handler somewhat
>faster than the bit time.  I have successfully built a software UART using a
>interrupt 6x of the bit rate. I expect 5x would work pretty well.

You get away with 4 samples per bit time if you are not doing it synchronous to
the bit edges. Many years ago before high speed async modems were commonly
available we used to send async data through synchronous modems, and could do it
with no errors if the async baud rate was a quarter of the sync modem rate.

'Flash Card in General [EE]'
2000\05\28@080628 by Martin McCormick

flavicon
face
       Has anybody installed a connector to a flash card that
will work on a perph board under wire-wrap technology?

       Also, How many write cycles can one get away with to a
smart media card?

       I would be using one instead of a cassette tape in an
audio storage device that would constantly be recorded,
listened to, and then reused.

       Of course, everything else in my project is 5-volt logic,
but that's a minor problem if everything else would work as
hoped.

Martin McCormick 405 744-7572   Stillwater, OK
OSU Center for Computing and Information services Data Communications Group

'[EE] Flash and EEPROM based file systems'
2000\05\28@082709 by Bob Ammerman

picon face
Flash file systems are tricky. You have to worry about load-leveling. It
wouldn't do to continually write, for example, the FAT and have it wear out
before the rest of the space.

Bob Ammerman
RAm Systems
(high function, high performance, low level software)

{Original Message removed}

'[PIC]: [EE]: Microcontroller with 4 USARTs'
2000\05\28@082711 by Bob Ammerman

picon face
Of course this depends on the quality of your signal.

This thread has got me to thinking, and coding, and I am pretty sure I've
come up with a way to get 4 in and 4 out at 31250buad on a PIC18CXX2 at 10
MIPS. The trick involves accumulating input samples on each channel and
processing them 5 at a time instead of one-by-one. This idea was inspired by
byte-at-a-time CRC algorithms. Basically you end up with a monster state
machine, about 70 states, with 32 (ie: 2^5) possible inputs for each state.
The state machine is then stored as one whopping big (about 8K) table. But
hey, what's 8K when you've got 32K on chip? :-)

Bob Ammerman
RAm Systems
(high function, high performance, low level software).

{Original Message removed}

'[EE] Flash and EEPROM based file systems'
2000\05\28@103604 by Robert A. LaBudde

flavicon
face
<x-flowed>At 04:14 AM 5/28/00 -0400, you wrote:
>anyone have any code dealing with implementing a file system on either
>FLASH memory or any other type of memory.. I'd like to get a 1 MB flash
>chip and put a small filesystem on it but rather than try to design the
>thing myself I'd like to sample what's out there.. I haven't turned up
>much. I plan on using the Atmel SPI Flash memory chips and figure that
>with a 16 bit pointer I could have access to 4 MB I want to make a tiny
>file server :)

Because of the finite lifetime of eeprom, you might consider one of the
systems used for CD-ROM or CD-RW.

Or, a simple method is the use a linked list directory. When a file gets
replaced more than N times, mark the entry as deleted and replace it with a
new entry the first one is linked to. This results in slower directory
accesses, but predictable write cycling of memory.

Of course, if your data will be write-once and only appended to, you could
use one of the classic simple file systems, such as the CP/M-DOS FAT16
method (well-documented in the IBM Technical Reference Manual for the PC,
or in Dr. Dobbs).

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: spamralspam_OUTspamlcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causas scire"
================================================================

</x-flowed>

'[EE] Wireless communication...'
2000\05\28@170308 by Jilles Oldenbeuving

flavicon
face
Hi...


For prototypeing purposes we bought a couple of 4 pins 'complete AM radio
transmitters' from R.F. Solutions. Also bought
a couple of matching receivers ofcourse (433 MHz). (http://www.rfsolutions.com).
My problem with them is this: when supplying Vcc (5V) and GND to the
transmitter and connecting a function generator
at the data in, of 2 kHz, 50 % dutycycle (coupled AC or DC) i can't see
anything at the receiving end. I can't measure
if the transmitter is actually oscilating at 433 MHz becouse the fastest
scopes we have is a Philips 200 Mhz scope...

Also the datasheets and the technical support are far beneath appropiate, in
my opinion.

The units were places 20 cm apart and had just a wire of 15 cm as an
antenna. Anybody couped with the same problem?
Anyone have experience with these modules (i mean the AM-RT4-433 transmitter
and the AM-HRR-433 receiver, of RF Solutions)

Jilles

'[EE] Microcontroller with 4 USARTs and 40 pins'
2000\05\28@171749 by Edson Brusque

face
flavicon
face
> >If it don't say anything more, it may be the classic 8051's: one machine
> >cycle is formed by twuelve clock cycles, and the instruction cycle
> >depends on the particular instruction.
> >If You want more speed enhacement look at Dallas MCS-51 compatible,
hi-speed
> >micros.
> Or the AVR, at one xtal clock per instruction (a few take two). 8 mhz, but
> that's 96 to an 8051 apparently.

   Ok, but beside the Scenix, there's no 8-bit microcontroller capable of
doing more than 20 MIPS???

   And what about the 16-bit micros? Can it be a good option for my
project? A US$10-20 microcontroller isn't very expensive to me if it can do
all I need on this project.

   Best regards,

   Brusque

'[EE] Info: Rechargeable Lithium coin cells'
2000\05\28@172841 by Jilles Oldenbeuving

flavicon
face
Have you also stumbled on some charge circuits for secondary cells? If you'd
know some good web-site for it,
please let me know....


Jilles
-----Oorspronkelijk bericht-----
Van: Russell McMahon <STOPspamapptechspam_OUTspamspamBeGoneCLEAR.NET.NZ>
Aan: spam_OUTPICLISTspamspamBeGoneMITVMA.MIT.EDU <EraseMEPICLISTspamKILLspamMITVMA.MIT.EDU>
Datum: zondag 28 mei 2000 13:05
Onderwerp: [EE] Info: Rechargeable Lithium coin cells


>I went looking for info on rechargeable Lithium coin cells and found it
very
{Quote hidden}

'[EE][PIC] How to measure level of liquids and sens'
2000\05\28@174123 by Hugo Jorge Mller

flavicon
face
Hello

I am beginning to work in the final project of my career of Electronic
Engineering and at the moment, we have decided to make the following work
(with a friend): To automate a plant of Concrete.

The idea is to use a PC for the general control of the plant and to arm a
network (Possibly RS485) with terminals that will be slaves working with
PICs, to complete different tasks, as the following ones:

1) To control the pneumatic servos and read proximity sensores and other.

2) To Sense the weight of the materials with cells of loads, indicate the
value measured in a  7 segments display and to send the measures througt the
network when they are requested or periodically. This partly would be
resolved, but I accept ideas and suggestions in this respect.

3) To Sense the level of water in the main dosificador tank. The tank should
be filled until certain level and then it is pumped to the truck concrete
mixer. I have think in sense the height of the column of liquid with a
sensor of pressure Motorola of the series MPX, I also thought of the
ultrasonic solution  but I don't have idea that resolution i can achieve.
The tank in question has 1100 Liters and a height of about 2 meters. aprox.,
it is cylindrical. I need a precision of about 5 liters. (or better).
Ideas? Comments? Other viable methods?
On the other hand I should dose some aditives, special liquids that
unfortunately they are corrosive and at the moment it is filled a small tank
of about 26 liters by means of a key, for graveness, then they closes this
key (superior) and two keys open up, one in the inferior part that allows
the exit of the preservative toward the MIXER and the other one in the
superior part that injects compressed air at 10 Kg/cm^2 to impel to the
preservative and to pump it without having contact with the same one.
The problem is to measure the level or the quantity of this aditive without
touch it and to be able to pump it too to the mixer.
I thought of measuring it with sensor MPX, but the problem is when opening
the key of compressed air, the sensor doesn't support 10 Kg/cm^2 (although
it could measure in differential form, but I suppose that the transitory one
provoked, it would destroy to the silicon sensor).
Here it is where I request them help that mensuration methods advise me?

Somebody had worked with sensor MPX with PICs ?  What kind of interface/ ADC
use ?

4) Another topic not less difficult of solving it is to be able to measure
the relative humidity that there is in the sand and in the concrete once
blended. Here the only method that I am happened (electronic) it is between
two by means of the mensuration of conductivity electrodes of a material
that is not oxidized, located inside the material to measure, at a certain
distance. That other methods or variantes suggests me?

As for the net RS485, has somebody used them with PICs? That protocols
suggest? Some link with information?

Good, I won't extend more in the detail, I wait their collaboration with
ideas...

Sorry if there are errors in the text, but my language is Spanish  :-)

Thank you from already.

Hugo J. M|ller
H.J.M. Hardware & Software Diseqos Electrsnicos
San Nicolas 683
Tel-Fax : 54-(0)-343-424-5953
(3100) Parana (Entre Rmos) Argentina
Email : hmuller [ANTISPAM-QUITAR-ESTO] @arnet.com.ar
Web Site: http://www.pagina.de/hjm
UIN (ICQ) : 38.605.074

'[EE] Wireless communication...'
2000\05\28@174746 by Jim P

flavicon
face
     "  ...Philips 200 Mhz scope...  "

... should still see something as that is usually the
"3 dB point" for the scope's bandwidth ... I once trouble
shot a Tektronix 454 (150 MHz scope) trigger circuit using
just a 10 MHz bandwidth Tek portable - the trigger circuit
incorporated a tunnel diode that excited a 'tank' circuit that
resonated at several hundred MHz ... the indication was only
a small 'blip' when the tunnel diode was working as seen on
the low bandwidth scope.

Take a look at the xmtr with the Philips scope -  433 MHz
is just over an octave higher frequency - and the scope
should show enough to give a yea/nay indication.

Watch out for the the scope probe though - they often have a
much lower cutoff freq than the scope itself. You may have to
rig a short piece of coax and if the scope has a built-in 50 Ohm
termination switch it it to then couple the xmtr output directly
into the scope.

Zero dBm is about .223 V RMS (.6 V Pk-Pk) less any rolloff
in amplitude the scope shows at 433 MHz.

Jim P

{Original Message removed}

2000\05\28@180453 by Jilles Oldenbeuving

flavicon
face
{Quote hidden}

Hmmm, you're right i guess. But the scope is a digital one. Even when i
measure a
voltage that goes from 0V to 5V it takes approx. 3 seconds to adjust the
screen. What
one will see is this:

0V -----------------------------

('bout 1 sec later:)


5V       .                 .
0V -----  -------------  ------------

again, 1 sec later:


5V   --    ---      ---
0V --   ---    ----   ----

and, finaly after about 3 seconds:


5V -----------


I think this has to do with how the A/D converter works within the scope...
If i measure a point were
i *suspect* to be 433 MHz all i see is something like 3/4 Vcc, wich could be
the avarage voltage?
I want to say that i mustn't have to measure these 'ready to go'-modules! I
mean, they have to work, don't they?
The only thing i could find on the website of RF Solutions was a ****3****
page datasheet. And after asking some
application information, they reffered to book! That application information
had to be in the datasheet in my humble opinion...
(frustrated, you guessed it right :)

Did anyone get these modules to work? I'm interested in how they did it.

Jilles

2000\05\28@190512 by Jim P

flavicon
face
Oh - digiscope ...

Do you have any small signal diodes like types 1N914
or 1N4148 diodes on hand?

If these are 'AFSK'  (AM or amplitude or Pulse modulation) a quickie
"RF detector" can be rigged and the data can be 'demodulated' and
seen with a low freq scope.

A DC voltage will also be produced - verifying the prescence of RF.

ckt:

RF from xmtr to a  50 Ohm  Resistor (load for RF)  to ground ---
--- Anode_diode_Cathode -----  1 K Resistor to gnd --- scope Input


Might also place a 470 pF cap to ground across the 1K R.

Schematically (if this comes through):

RF In---------o ------|< -----o-------o- to scope
                      |                       |           |
                  R 50                 R 1K     470 pF
                      |                       |           |
                     _                      _          _


Hope this helps.

Jim P.





{Original Message removed}

'[EE] LED Challenged'
2000\05\28@200640 by Ed Edmondson

picon face
I guess I am really "LED Challenged" as I can't find a circuit that will dim
an LED used as a backlight.  The LED has a Vf of 3.5 to 4.0 volts @ If of 20
mA.  I want to run it off 5 volts and want to vary the intensity from "Off"
to "On" (less the drop across the Vbe) using a 2N3904?  I figured the LED
limit resistor to be about 45 ohms (5 - .6 - 3.5)/.020) ?  Is this right?

How do I vary the base drive to vary the LED intensity?  A resistive divider
with a pot?  How do I calculate the values for the divider?  The 2N3904 has a
hfe of 100 to 300.  Does anyone care to help me out?

Regards,
Ed

'[EE]:[PIC]: How to measure level of liquids and se'
2000\05\28@201049 by Gennette, Bruce

flavicon
face
       Looks do-able to me.

       Reading proximity sensors, reading load cells and displaying values
on request while regularly logging them is simple PIC stuff.

       Measuring liquid heights can be done several ways, but as you are
already reading proximity switches why not use that method for this task
too?  Use a captive rod in a guide above a float to trip proximity switches
above your tanks (KISS principle).  Also gives a visual indication of the
amount in the tank as the rod rises above the rim.

          ______  _
            ||  <||
            ||x <|| sensors
            ||  <||
          _ || _ ||
       ___| || |_||_________
       |  | || |           |
       |  | || |           |  Use courier font to see diagram
       |    ||             |
       | ___||___          |
       |_|float |__________|
       | |______|          |
       |                   |
       |       liquid      |
       |                   |
       |___________________|

       This should also work for your special additive liquids as long as
you use compatible materials for the float and rod.  For increased accuracy
use tall, thin tanks (large, vertical pipes?).

       Humidity sensors are available in 1-wire devices.  [I assume you
need to know the humidity in several feeds to guess the amount of water
contained in the raw materials (sand and gravel) to calculate the real
amount of material being added and the water to be added]

       Good luck.

       <original message>

       To automate a plant of Concrete.

       The idea is to use a PC for the general control of the plant and to
arm a
       network (Possibly RS485) with terminals that will be slaves working
with
       PICs, to complete different tasks, as the following ones:

       1) To control the pneumatic servos and read proximity sensores and
other.

       2) To Sense the weight of the materials with cells of loads,
indicate the
       value measured in a  7 segments display and to send the measures
througt the
       network when they are requested or periodically. This partly would
be
       resolved, but I accept ideas and suggestions in this respect.

       3) To Sense the level of water in the main dosificador tank.
       <snip>

'[EE] Microcontroller with 4 USARTs and 40 pins'
2000\05\28@202332 by Byron A Jeff

face picon face
On Sun, May 28, 2000 at 06:21:24PM -0300, Edson Brusque wrote:
> > >If it don't say anything more, it may be the classic 8051's: one machine
> > >cycle is formed by twuelve clock cycles, and the instruction cycle
> > >depends on the particular instruction.
> > >If You want more speed enhacement look at Dallas MCS-51 compatible,
> hi-speed
> > >micros.
> > Or the AVR, at one xtal clock per instruction (a few take two). 8 mhz, but
> > that's 96 to an 8051 apparently.
>
>     Ok, but beside the Scenix, there's no 8-bit microcontroller capable of
> doing more than 20 MIPS???
>
>     And what about the 16-bit micros? Can it be a good option for my
> project? A US$10-20 microcontroller isn't very expensive to me if it can do
> all I need on this project.

A piece of advise. Stick to environments you know instead of striking out.
Especially when your striking out for more MIPS because you want them for
something that's easily done in hardware.

I'd advise sticking with PICs. Let me throw out a couple of suggestions.

1) I'm planning on using a Cirrus Logic CL-CD180 octart. Unfortunately Cirrus
Logic has obsoleted the part. In fact they've spun off their communcations line
into Basis Communications. I have a couple of samples and an incomplete
data sheet. If anyone has the pinout I'd really appreciate it. I liked the
part because of the number of serial ports and the fact that it came in a
84 pin PLCC package making it easy to use to hobby work. Basis Comm does have
an updated version the CL-CD1865. But it comes in a 100 pin PQFP. Not real
easy to prototype with.

2) My second choice was to build an intelligent UART out of a PIC. Specifically
for MIDI conversion of the stream into events with timestamps would be
very useful. Also having buffering so that the main processor can dump
events ahead of time and have the intelligent MIDI UART deliver them to the
channel at the appropriate time. Also doing MIDI channel mapping, splits and
volume control in the UART seems interesting. It's also interesting to consider
direct transmission of events from one UART to another bypassing the main
processor.

A single software channel can easily be handled by a 12C509 with a software
UART. Of course developing the UART code, the interface to the main processor,
(probably something I2Clike) would take some effort. But once it's done
any number of channels could be added to the system and the main system
wouldn't have to be uberpowered.


Maxim has an interesting discussion in their MAX3100 intro describing the
issues of software UARTs. You can find it here.

http://dbserv.maxim-ic.com/tarticle/view_article.cfm?article_id=53

The bottom line IMHO is that the traditional approach is better than the
Winmodem approach because you end up having a highly overpowered processor
just so that you can have the MIPS to bit bang UARTS. Just remember that
8 12C509's will give you 8 MIPS just for the UARTS. Think about the
distributed processing solution.

BAJ

'[EE]: Wireless communication...'
2000\05\28@202749 by Jim P

flavicon
face
I visited http://www.rfsolutions.com web page - but could not
find any references to the RF data rcvrs/xmtrs. Looks
like they are 'repping' various other lines of RF products
as well as providing other RF engineering services targetted
for wireless system's operators (cellular, PCS, trunked 2-way,
etc).

I've reviewed Linx Technologies products (link below) in the
past - never bought any of their product (except some of the
900 MHz rubber ducky antennas and samples of their 'patch'
antennas). It looks like they have done their homework - they
basically have three tiers of miniature RF data OEM-level
product, each one offering improved performance/features.

http://www.linxtechnologies.com/f_modules.html

They have detailed technical material of their product in pdf form -

They also offer some ready-made eval boards - hook up RS-232
and go!

http://www.linxtechnologies.com/m_evalkitdata.html

Jim P.

{Original Message removed}

'[EE] LED Challenged'
2000\05\28@214626 by Bob Ammerman

picon face
Use PWM (pulse width modulation).

Assuming you are driving this with a PIC. Some PICs have built in pulse
width modulators.

Alternatively, since you don't need a particularly fast output, you could do
it in software, perhaps driven off a timer interrupt.

Bob Ammerman
RAm Systems
(high function, high performance, low level software)

{Original Message removed}

'[EE] Flash and EEPROM based file systems'
2000\05\28@220119 by Damon Hopkins

flavicon
face
"Robert A. LaBudde" wrote:
{Quote hidden}

I was thinking of a fat16 type of system I'll work of my hand scribbled
notes into an HTML document if anyone would be willing to look at it and
HOPEFULLY give me suggestions or ideas.. the main purpose of the file
system would be to have multiple files that are mainly read. there
should be very little writing.. I'm thinking about this as being used in
a web server type application.

                       maybe I should write it out in HTML anyway just to MAKE myself be
more specific :)

                       Damon Hopkins

'[EE] Info: Rechargeable Lithium coin cells'
2000\05\28@220534 by Damon Hopkins

flavicon
face
Jilles Oldenbeuving wrote:
{Quote hidden}

I have tons of links for rechargeable battery chargers if you want me to
post them let me know..

                       Damon Hopkins

2000\05\28@220744 by Dan Michaels

flavicon
face
Russell McMahon wrote:
>I went looking for info on rechargeable Lithium coin cells and found it very
>hard to find anything technical.
>Here's the best of my slim pickings.
.........

Checkout the following for another portal site to mine:

http://www.ibatteries.com

'[EE] Microcontroller with 4 USARTs and 40 pins'
2000\05\28@221341 by Bob Ammerman

picon face
There are some good ideas here, but you have moved the data movement problem
from SERIAL<->PIC to be PIC<->PIC. You're still going to need some hefty
horsepower to do the PIC<->PIC transfers. Remember, the main processor has
to handle all channels at once. MIDI waits for no man (nor PIC) :-)

Bob Ammerman
RAm Systems
(high function, high performance, low level software)

{Original Message removed}

'[PIC]: [EE]: Microcontroller with 4 USARTs and 40 '
2000\05\28@221344 by Bob Ammerman

picon face
This thread has fascinated me from the beginning. I was sure that it was
possible to do this on a PIC.

What I have come up with so far:

I have designed, and written the critical code for, a scheme permitting 5
full-duplex software UARTs. This code requires a timer-driven interrupt at 5
times the baud rate. Code path in the interrupt handler, counting all
overhead, with all 5 channels going full blast in both directions, is 55
instruction times max, 51 instruction times average. This drops down
somewhat if the channels are running at less than full speed.

The simulated UARTS sample the input at 5x the baud rate, and determine bits
using the majority vote of the center 3 samples for each bit.

They detect framing errors, and can handle receive data streams slightly
faster than the nominal rate (ie: the stop bit can be less than 5 samples
long, so the UART can slip properly to handle a  slightly overspeed input).

Both receive and transmit are double-buffered so that task level has an
entire byte time to handle a received character or prepare the next
character for transmission.

Relating this to the problem at hand:

On a 10MIP 18CXX2 chip (10MHz clock, PLL'd to 40MHz on chip), with a baud
rate of 31250, the interrupt rate would be every 64 instruction times. This
will leave at least 9 and on average 13 instructions between interrupts.

Thus, 'task level' code will get about 13/64 = 20% or so of the 10MIPs.  You
can get quite a bit done with the remaining 2 MIPS!

For anyone who is interested, the basic structure of the interrupt handler
is something like this (expressed in a combination of pseudocode and "C" to
make it easier to follow, but the real code is of course assembly):

send values computed by last interrupt for output bits to the hardware

fetch current values input bits from the hardware into 5 5-bit shift
registers, one per channel.

switch (phase)
{
case 0:
   phase = 1;
   compute next output bit for channel 0
   process last 5 input bits received by channel 0
   break;

case 1:
   phase = 2;
   compute next output bit for channel 1
   process last 5 input bits received by channel 1
   break;

case 2:
   phase = 3;
   compute next output bit for channel 2
   process last 5 input bits received by channel 2
   break;

case 3:
   phase = 4;
   compute next output bit for channel 3
   process last 5 input bits received by channel 3
   break;

case 4:
   phase = 0;
   compute next output bit for channel 4
   process last 5 input bits received by channel 4
   break;
}

The phrase 'compute next output bit for channel N' simply figures out what
start, data, or stop bit is to be sent.

The phrase 'process last 5 input bits received by channel N' involves using
the 5 input bits, treated as a 5 bit number, as an input to a large state
machine stored as a table in program memory. This will determine a new
state, and possibly an action to be performed (setting a bit in the receiver
register, or marking a byte received (correctly or with a framing error)).

Bob Ammerman
RAm Systems
(high function, high performance, low-level software)

'[EE] LED Challenged'
2000\05\28@223031 by Robert A. LaBudde

flavicon
face
<x-flowed>At 08:06 PM 5/28/00 -0400, you wrote:
>I guess I am really "LED Challenged" as I can't find a circuit that will dim
>an LED used as a backlight.  The LED has a Vf of 3.5 to 4.0 volts @ If of 20
>mA.  I want to run it off 5 volts and want to vary the intensity from "Off"
>to "On" (less the drop across the Vbe) using a 2N3904?  I figured the LED
>limit resistor to be about 45 ohms (5 - .6 - 3.5)/.020) ?  Is this right?
>
>How do I vary the base drive to vary the LED intensity?  A resistive divider
>with a pot?  How do I calculate the values for the divider?  The 2N3904 has a
>hfe of 100 to 300.  Does anyone care to help me out?

The emitter voltage is the base voltage V(B) minus the diode drop of 0.7 V.
The voltage across the emitter resistor determines the emitter current. The
emitter current is the collector current I(C) (99+%).

So use a voltage divider to generate a voltage V(B) such that

        I(C) = (V(B)-0.7))/R(E)

The maximum current you will be able to get with 5.0 V is

        I(C)max = (5-0.7-3.5)/R(E) = 0.8/R(E)

For this to equal 20 mA, you'll need R(E) = 40 ohm.

However, I believe you've got a mistaken impression on the LED voltage
drop. They usually start about 1.7-2.0 V. In this case

        I(C)max = (5.0-2-0.7)/R(E) = 2.3/R(E)

and you'd need R(E) = 110 ohm.

Also, modern diodes have the same brightness at 5 mA as the original ones
did at 20 mA. You might do better to get by with 0-10 mA instead of 20 mA.

Assuming a 150 ohm resistor for R(E) (to be conservative), then

        I(LED) ~ I(C) ~ (V(B)-0.7)/R(E)

and you set V(B) with a voltage divider. The r(B) will be about beta*150
ohm, or about 20k. You need voltage divider resistors of about 2k to avoid
feedback from the base current.

In summary, use a 2k pot as a voltage divider, backed by 200 ohm resistors
at its ends (unless you want to go fully to saturation and cutoff), use a
150 ohm emitter resistor, and put the LED across the +5 V and collector.

Once you've determined the brightness you want, replace the pot with fixed
resistors.



================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: RemoveMEralTakeThisOuTspamlcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causas scire"
================================================================

</x-flowed>

2000\05\28@232516 by Bob Blick

face
flavicon
face
>However, I believe you've got a mistaken impression on the LED voltage
>drop. They usually start about 1.7-2.0 V. In this case

The original poster probably had the drop right.
Backlit LCD displays I've used have a series+parallel string and you have
the equivalent of 2 series LEDs.

Back to the original topic, is it neccessary to have infinite levels? Why
not just 3 levels controlled by two pins, each driving a transistor and
resistor.

If you decide to so software PWM, make it very regular, or you'll notice
pulsing as the PIC does different tasks(especially if you do a timer based
interrupt and sometimes shut off interrupts!).

-Bob

- Every day, computers are making people easier to use -

'[EE]: Wireless communication...'
2000\05\28@232722 by David Huisman

flavicon
face
We also have wireless data link modules.
http://www.orbitcoms.com

regards
David Huisman
Orbit Communications
@spam@infoSTOPspamspamorbitcoms.com
NSW
Australia

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