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'Batterys!!'
1999\02\13@124831 by rideout

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Anyone know what is the smallest size batteries that would be best for
the 16f84?
What I am trying to do is build a small transmitter which has a 555 and
a 16f84. If I use AAs the transmitter would not be small anymore.
Any suggestions?

Thanks
J. Rideout

1999\02\13@143643 by Brian Aase

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> Anyone know what is the smallest size batteries that would be best for the
> 16f84? What I am trying to do is build a small transmitter which has a 555
> and a 16f84. If I use AAs the transmitter would not be small anymore. Any
> suggestions?

First off, if you're looking for long battery life, don't use a
regular NE555!  They are power hogs.  Look at the TLC555
or something similar to that.

The size and shape of your project has a lot to do with
which battery you choose.  Are N cells too big?

1999\02\13@160107 by Mike Keitz

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On Sat, 13 Feb 1999 11:34:39 -0700 Brian Aase <spam_OUTulcsaTakeThisOuTspamESKIMO.COM> writes:
>> Anyone know what is the smallest size batteries that would be best
>for the
>> 16f84? What I am trying to do is build a small transmitter which has
>a 555
>> and a 16f84. If I use AAs the transmitter would not be small
>anymore. Any
>> suggestions?
>
>First off, if you're looking for long battery life, don't use a
>regular NE555!  They are power hogs.  Look at the TLC555
>or something similar to that.

Of course use a CMOS 555 if you have to, but usually the 555's function
can be included in the PIC software.  Lithium cells with output of 3V are
made in a very wide range of sizes.  A 16F84 will work fine from 3V or a
little less as the battery runs doem.  Pick the lithium cell that matches
the battery life you need.

If your project needs a relatively large amount of power so it will
require battery replacement more than once or twice in its expected
lifetime, alkaline batteries are much easier for a consumer to find and
less expensive to buy.  In terms of capacity per dollar / per volume,
alkaline AA or AAAs are a good choice.


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1999\02\13@162851 by Wagner Lipnharski

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Use those round cells LR-44 used in electronic pets, it is 1.5V and can suppy ar
ound 100mA/h, or more.  3 or 4 together (4.5-6V) use half the space of a single
AA.
Wagner

rideout wrote:
>
> Anyone know what is the smallest size batteries that would be best for
> the 16f84?
> What I am trying to do is build a small transmitter which has a 555 and
> a 16f84. If I use AAs the transmitter would not be small anymore.
> Any suggestions?
>
> Thanks
> J. Rideout

1999\02\13@165617 by dave vanhorn

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>> Anyone know what is the smallest size batteries that would be best for
>> the 16f84?
>> What I am trying to do is build a small transmitter which has a 555 and
>> a 16f84. If I use AAs the transmitter would not be small anymore.
>> Any suggestions?


Just for grins, what is the 555 doing that the F84 can't do?

1999\02\13@174542 by rideout

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using the 555 to create a carrier freq. of 38 kHz. using the 16F84 to
continually output serial. There is no way the 16F84 can create its own
carrier freq. and transmit onto it all at the sam time.

dave vanhorn wrote:
>
> >> Anyone know what is the smallest size batteries that would be best for
> >> the 16f84?
> >> What I am trying to do is build a small transmitter which has a 555 and
> >> a 16f84. If I use AAs the transmitter would not be small anymore.
> >> Any suggestions?
>
> Just for grins, what is the 555 doing that the F84 can't do?

1999\02\13@181117 by dave vanhorn

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At 07:12 PM 2/13/99 -03-30, rideout wrote:
>using the 555 to create a carrier freq. of 38 kHz. using the 16F84 to
>continually output serial. There is no way the 16F84 can create its own
>carrier freq. and transmit onto it all at the sam time.

I think you're wrong :)

Use the timer to give you a 76 khz interrupt, a flag to say wether the tone
is to be on or off, and a few timer bytes for duration and such. Your ISR
needs to be short, but you can do other things in the foreground to set up
for the next byte etc.

I work with ints up to 300kHz in the atmel, but I get a mips per Mhz :)

1999\02\13@182406 by Mike Keitz

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On Sat, 13 Feb 1999 19:12:38 -0330 rideout <.....srideoutKILLspamspam@spam@NF.SYMPATICO.CA>
writes:
>using the 555 to create a carrier freq. of 38 kHz. using the 16F84 to
>continually output serial. There is no way the 16F84 can create its
>own
>carrier freq. and transmit onto it all at the sam time.

Sure it can.  Appearing below is my routine to transmit to a Magnavox VCR
using a 4 MHz PIC crystal.  For short range, it works to drive the IR LED
from a PIC pin through a resistor.  Longer range would need a driver
transistor to apply about 100 mA peak to the IR LED.

It also handles rearranging the bits so I can just feed in an 8 bit code
corresponding to the button code to be sent, and Manchester codes the
data.  If you're using another scheme that doesn't use Manchester code,
you'd need to change the program considerably.  But the concept is the
same.  It pulses the LED on and off while it is counting and shifting and
deciding what to send next.

Looking at the code, you'll realize this kind of routine isn't
particularly easy to write, but it can be done.


;-------------------------------------------------
; IR sending routine
; Variables:
; irdat: 2 bytes of which 14 bits are used.  Sent MSB first.
; ii : counts cycles of IR (from 52 to 0)
; jj : counts bits sent from irdat
; Enter here with 7 bit code in W.0-W.6 and the A bit in W.7
;  uses irdat, irdat+1, ii, jj
sendir
       movwf   irdat           ;Set low byte
       rlf     irdat,f
       movlw   b'01000010'     ;Hi byte (assuming dA=00)
       movwf   irdat+1
       btfsc   irdat,7
       bsf     irdat+1,5       ;Set the high data bit.
       skpnc                   ;Skip if A bit is 0
       bsf     irdat+1,4       ;Set A bit = 1.
       bsf     irdat,7         ;irdat now 1ddddddX
; Here with irdat set up. (X1dA0010 1ddddddX)
; Set up the loop controls.
       movlw   .15             ;Send 14 bits (compensate for
predec)
       movwf   jj
; Here to (possibly) start a new bit.
sendirn
; 7 cy
       decf    jj,f            ;Dec. the bit counter.
       skpnz                   ;Skip if more bits remain.
       goto    sendird         ;Sending complete.
       rlf     irdat,f         ;Move other bits up
       rlf     irdat+1,f       ;Move new bit up into MSB of irdat+1
       movlw   .66             ;Each bit is 66 cycles of IR.
       movwf   ii
;  Here at the start of each IR pulse.
sendirp
; Turn LED off.
       movfw   mirrorb         ;Get PORTB data (with LED
off)
       movwf   PORTB           ;Turn LED off.
;  Decide if the LED should be on or off.
; 6 cy
       movlw   0 - .33         ;Constant for 1/2 pof period.
       addwf   ii,w            ;C set if in first half of
period.
       rlf     ii,w            ;Get C flag into W.0 (could use
any reg)
       andlw   b'00000001'     ;Keep only one bit.
       btfsc   irdat+1,7       ;Skip if sending 0
       xorlw   b'00000001'     ;If sending 1, IR on late.
; Now have W.0 set if IR should be on.
       nop
       goto    $+1
       goto    $+1
       goto    $+1
       iorwf   mirrorb,w       ;OR in other bits for PORTB.
       movwf   PORTB
; (11 cycles from here back to sendirp, 13 cy till LED off.)
       decf    ii,f            ;Another pulse in this bit?
       skpnz                   ;Yes. (Additional delay)
       goto    sendirn         ;No, get another bit (if
needed)
       nop                     ;Compensate for not loading another
bit.
       goto    $+1
       goto    $+1
       goto    sendirp         ;Do another pulse.
; Here when sending complete.
sendird
       movfw   mirrorb
       movwf   PORTB           ;Be sure LED is off.
       goto    d50ms           ;Always delay after each send
(return via
                               ; d50ms)




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1999\02\13@183442 by rideout

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yep, its not easy to write. I think I'll stay with the hardware. right
know I have the code written that outputs continually at 2400 baud into
the 555 that has a carrier of 38 kHz. A receiver module picks it up at
this freq. and subtract the carrier.

Thanks any way!

Mike Keitz wrote:
{Quote hidden}

1999\02\14@043120 by David Duffy

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rideout <.....srideoutKILLspamspam.....NF.SYMPATICO.CA> wrote:
> yep, its not easy to write. I think I'll stay with the hardware. right
> know I have the code written that outputs continually at 2400 baud into
> the 555 that has a carrier of 38 kHz. A receiver module picks it up at
> this freq. and subtract the carrier.

Recently I did an IR transmitter that used a F84 to do data + carrier.
I took the (easy ?) way out and modified my delay loop subroutine that
is called to time the data bits to toggle the IR out pin while in the loop.
That took only a few minutes to work out. The carrier is not mega-critical
frequency-wise as the receivers demodulator strips it out anyway. You
just have to be near the sweet spot to get the best range from it. Just
make it so the duty cycle is roughly 50/50.
Regards...

1999\02\14@084535 by w. v. ooijen / f. hanneman

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Why not? I used a 16x84 to output a modulated IR signal (OK, it was 30kHz
but that does not make much difference...).
I did not notice what you are trying to do, but sending asynchronous (rs232
)
sigmal over IR to a canned receiver does not work well (at least not for
all characters) because the receiver is moptimized for a a signal with
50% duty cycle.
regards,
Wouter.

----------
{Quote hidden}

for
> > >> the 16f84?
> > >> What I am trying to do is build a small transmitter which has a 555
and
> > >> a 16f84. If I use AAs the transmitter would not be small anymore.
> > >> Any suggestions?
> >
> > Just for grins, what is the 555 doing that the F84 can't do?

1999\02\14@093019 by Andy

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-----Original Message-----
From: dave vanhorn <@spam@dvanhornKILLspamspamCEDAR.NET>
To: KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU <RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU>
Date: 13 February 1999 21:56
Subject: Re: Batterys!!

Try http://www.lprs.co.uk (I think) you will find loads of small tx/rx stuff for
digital apps, bear in mind how performance changes relative to frequency and
you might be able to use smaller batteries by using a more apropriate
(eficient) frequency and who knows one day i may even be able to spell!

Andy


>>> Anyone know what is the smallest size batteries that would be best for
>>> the 16f84?
>>> What I am trying to do is build a small transmitter which has a 555 and
>>> a 16f84. If I use AAs the transmitter would not be small anymore.
>>> Any suggestions?
>
>
>Just for grins, what is the 555 doing that the F84 can't do?
>

1999\02\15@101436 by Harrison Cooper

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Don't you want to be generating a sine wave rather than a square wave for
RF? Or did I miss something here...

{Original Message removed}

1999\02\15@105243 by John Payson

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|Recently I did an IR transmitter that used a F84 to do data + carrier.
|I took the (easy ?) way out and modified my delay loop subroutine that
|is called to time the data bits to toggle the IR out pin while in the loop.
|That took only a few minutes to work out. The carrier is not mega-critical
|frequency-wise as the receivers demodulator strips it out anyway. You
|just have to be near the sweet spot to get the best range from it. Just
|make it so the duty cycle is roughly 50/50.

I thought I read somewhere that using a shorter "on" cycle
would help maximize the range/power (a 25% duty cycle will
give somewhat less range than 50%, but will only use half
the power).  Since using a shorter duty cycle will usually
allow the peak power to be safely increased, this will (with-
in certain limits) be a net win.

1999\02\16@120137 by w. v. ooijen / f. hanneman

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>>Just make it so the duty cycle is roughly 50/50.
> I thought I read somewhere that using a shorter "on" cycle
> would help maximize the range/power (a 25% duty cycle will
> give somewhat less range than 50%, but will only use half
> the power).  Since using a shorter duty cycle will usually
> allow the peak power to be safely increased, this will (with-
> in certain limits) be a net win.

Does anyone have real figures or experience with this optimization?

regards,
Wouter.

1999\02\16@121555 by dave vanhorn

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At 08:02 AM 2/16/99 +0100, w. v. ooijen / f. hanneman wrote:
>>>Just make it so the duty cycle is roughly 50/50.
>> I thought I read somewhere that using a shorter "on" cycle
>> would help maximize the range/power (a 25% duty cycle will
>> give somewhat less range than 50%, but will only use half
>> the power).  Since using a shorter duty cycle will usually
>> allow the peak power to be safely increased, this will (with-
>> in certain limits) be a net win.
>
>Does anyone have real figures or experience with this optimization?
>
>regards,
>Wouter.

True fact, but it depends on the speed of the reciever front end. If you go
too fast, then you get averaged down again.

1999\02\16@130019 by Scott Dattalo

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On Tue, 16 Feb 1999, w. v. ooijen / f. hanneman wrote:

> >>Just make it so the duty cycle is roughly 50/50.
> > I thought I read somewhere that using a shorter "on" cycle
> > would help maximize the range/power (a 25% duty cycle will
> > give somewhat less range than 50%, but will only use half
> > the power).  Since using a shorter duty cycle will usually
> > allow the peak power to be safely increased, this will (with-
> > in certain limits) be a net win.
>
> Does anyone have real figures or experience with this optimization?

Yes. I worked on a display project that attempted to use "high efficiency"
reg, green, and blue LEDs for illumination. Each color was illuminated for
1/3 of the time. The LED current was increased to 50% beyond the maximum
allowed DC level. The LED's were certainly brighter (we took measurements,
however I don't have that data available). On yet another project, I have
the need to do this same trick with IR LEDs. The data sheet explicitly
states that you may pulse the LED with a current larger than its nominal
DC value. For example, here are the specs of one led:

If = 20ma, Vf = 1.70V, Po = 0.5mW
If = 100ma, Vf = 2.10V, Po = 2.7mW

If you compare the efficiencies at the two drive levels, you'll notice
that the LED is about 15% more efficient at the lower drive level. But
it's possible to get more output power by applying "short" pulses. (BTW,
one of our clients supposedly pulses the LEDs with 1 amp! I'm not sure
what Vf or Po are though.)

I might also add that even though the efficiency drops when the LED is
driven harder, this is not usually a practical problem. Because most of
the LED drive circuits I've seen drive the LEDs from a voltage source and
regulate the current either with a resistor or a transistor. Now, if you
decided to servo the voltage source with a DC-DC converter...

Scott

1999\02\16@143526 by w. v. ooijen / f. hanneman

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> >>Since using a shorter duty cycle will usually
> >> allow the peak power to be safely increased, this will (with-
> >> in certain limits) be a net win.
> >
> >Does anyone have real figures or experience with this optimization?
>
> True fact, but it depends on the speed of the reciever front end. If you
go
> too fast, then you get averaged down again.

So what would be the optimum?

1999\02\16@151454 by dave vanhorn

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>> >Does anyone have real figures or experience with this optimization?
>>
>> True fact, but it depends on the speed of the reciever front end. If you
>go
>> too fast, then you get averaged down again.
>
>So what would be the optimum?

You'd have to measure the received signal at the photodiode and adjust, I
can't determine that from here :)

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