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'4 digit auto-ranging frequency-meter.'
1998\10\06@215546 by netquake

flavicon
face
part 0 988 bytes content-type:application/octet-stream; name="meter.gif"I ran into a very interesting PIC16C84 project: a 4 digit auto-ranging
frequency-meter
(made by Simone Benvenuti & Andrea Geniola) which uses virtually no parts.
Unfortunately the schematics provided lack some information. The type of
transistors
is not mentioned, neither the majority of resistor values, nor the type of
display.
I'm enclosing the schematic in case anybody can add some light to it.

Thank you very much.

--------------------------------------------
"I must not fear. Fear is the mind-killer.
Fear is the little death that brings total
obliteration. I will face my fear... I will
permit it to pass over me and through me."

Kwisatz Haderach - Dune

       netQ
<spam_OUTnetquakeTakeThisOuTspaminnocent.com>
Content-Type: application/octet-stream; name="meter.gif"
Content-Description: meter.gif (Imagen de Corel PHOTO-PAINT 7.0)
Content-Disposition: attachment; filename="meter.gif"

Attachment converted: wonderland:meter.gif (GIFf/JVWR) (0001967C)

1998\10\06@234437 by Sean Breheny

face picon face
Hi,

The transistors should be any NPN general purpose transistor (such as PN2222).

The resistors on the LEDs should be in the range of 100 to 300 ohms,
depending on the needed brightness and the supply voltage.

The resistors on the bases of the transistors should be around 10k.

I know these values because I have made similar display circuits before.

Good luck! Looks like a nice project!

Sean

At 09:27 PM 10/6/98 -0300, 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
shb7spamKILLspamcornell.edu  Phone(USA): (607) 253-0315 ICQ #: 3329174

1998\10\06@234446 by Sean Breheny

face picon face
Oops!

I forgot the one resistor, the one attached to MCLR. Its value is not
critical at all, in fact, you could just hook MCLR to V+. But, if you
prefer, you could add any resistor around 10k or so.

Sean


At 09:27 PM 10/6/98 -0300, 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
EraseMEshb7spam_OUTspamTakeThisOuTcornell.edu  Phone(USA): (607) 253-0315 ICQ #: 3329174

1998\10\06@234453 by Dave VanHorn

flavicon
face
>I ran into a very interesting PIC16C84 project: a 4 digit
auto-ranging
>frequency-meter
>(made by Simone Benvenuti & Andrea Geniola) which uses virtually no
parts.
>Unfortunately the schematics provided lack some information. The type
of
>transistors
>is not mentioned, neither the majority of resistor values, nor the
type of
>display.

The displays are seven segment common cathode, it looks like a 4 digit
multiplexed array, but four singles in paralell would work as well.

The base resistors arent' critical, 470 ohm or 1k should work.
The segment resistors are also uncritical, try 220-470. Depends much
on the display efficiency.

It's a cute project all right, hard to get less parts.

1998\10\06@234501 by jmnewp

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face
do you have any code for this? I would be interested in building it....

netQ wrote:
{Quote hidden}

1998\10\06@235510 by Valter Gruntar

flavicon
face
hi !

>From the schematic I can tell you this. For transistors you can use any NPN as B
C547, BC237 etc.,
resistors value between portA and BASEs of transistors are from 1K to 10K ohm,
resistors value for segments are around 390 ohm(even less to 270 ohm   5V-1,8V(V
-LED)=3,2V so
3,2V/270ohm=11,8mA for each segment) and finaly display can be any with common c
atode as HD1133X
the resistor from MCLR to +V is arround 1Kohm. All values are not critical.

Valter

netQ wrote:

{Quote hidden}

-content-type-CorelPhotoPaint.Image.8)
>                   Encoding: base64
>                Description: meter.gif (Imagen de Corel PHOTO-PAINT 7.0)

1998\10\07@000744 by Sean Breheny

face picon face
At 09:29 PM 10/6/98 -0500, you wrote:
>
>The displays are seven segment common cathode, it looks like a 4 digit
>multiplexed array, but four singles in paralell would work as well.
>
>The base resistors arent' critical, 470 ohm or 1k should work.

Do you really think THAT low? Even if the transistors were completely
saturated, I would expect the base resistors to be about 10 times the
segment resistors. If we used 470 ohm resistors on the bases, with a 5V
supply, we would have a base current of about 8mA. It would work fine, but
it would seem to me that for efficiency's sake, a few K would be better. It
would still throw the  transistors into saturation and save some power.

>The segment resistors are also uncritical, try 220-470. Depends much
>on the display efficiency.
>
>It's a cute project all right, hard to get less parts.
>

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
KILLspamshb7KILLspamspamcornell.edu  Phone(USA): (607) 253-0315 ICQ #: 3329174

1998\10\07@005848 by Regulus Berdin

flavicon
face
Dave VanHorn wrote:
> The displays are seven segment common cathode, it looks like a 4 digit
> multiplexed array, but four singles in paralell would work as well.
>
> The base resistors arent' critical, 470 ohm or 1k should work.
> The segment resistors are also uncritical, try 220-470. Depends much
> on the display efficiency.
>
> It's a cute project all right, hard to get less parts.

You can still minimize the parts by having the 7segment common anode,
make all the colllectors of the NPN transistors tie to the +5V supply
and reverse/invert drive to the LED (to the negative side).  This way
the base resistors is not needed anymore.

Reggie

1998\10\07@011346 by Dave VanHorn

flavicon
face
>>The base resistors arent' critical, 470 ohm or 1k should work.
>
>Do you really think THAT low? Even if the transistors were completely
>saturated, I would expect the base resistors to be about 10 times the
>segment resistors. If we used 470 ohm resistors on the bases, with a
5V
>supply, we would have a base current of about 8mA. It would work
fine, but
>it would seem to me that for efficiency's sake, a few K would be
better. It
>would still throw the  transistors into saturation and save some
power.


You have to allow for all seven segments to be on, plus worstcase of
the pic output drive..
A higher R will probably work. I'd use high eff red displays then, and
do the math. This is an off-the cuff shot.

1998\10\07@012626 by Dave VanHorn

flavicon
face
>You can still minimize the parts by having the 7segment common anode,
>make all the colllectors of the NPN transistors tie to the +5V supply
>and reverse/invert drive to the LED (to the negative side).  This way
>the base resistors is not needed anymore.
>
>Reggie

Are you SURE they will turn off? Look at the pin specs for minimum
high output voltage, and leakage current. I've got my doubts about the
current design, but IIRC, they can drive closer to ground than to VCC.

1998\10\07@032409 by Herman Theron

flavicon
face
Looks familiar.....

When I was at Technicon, I did a course on the PIC.  One of the
problems in the handbook was a Frequency Meter just like the one you
send.  We didn't came around doing the problem, but I've got some info
on how it works. If any one is interested let me know and I'll see if
I can get the info onto the pc.

Cheers
Herman

***********************************************
Herman Theron
Hermanus Magnetic Observatory (CSIR)
PO Box 32
Hermanus
7200
South Africa
Email: RemoveMEhetheronTakeThisOuTspamcsir.co.za
Tel: +27 283 21196
Fax: +27 283 22039
Cel: 0832973358
***********************************************

1998\10\07@035205 by Peter Gee

picon face
What would happen in the schematic shown if the input voltage when negative
with respect to the gnd of the PIC ?
my guess is that it wouldnt be good for the PIC.
in a similar project ( from memory), they use a coil, capacitor, signal
diodes, and a transistor to filter and switch the incoming frequency to make
it nicer for the PIC to count.
i built the project, and it seemed to give accurate results in comparison to
a bench frequency counter at a frequency of 40Mhz using a 10Mhz 16cf84.  (i
used an fm RC transmitter to calibrate it) -- i don't have a frequency
generator higher than that so i can't test its high end response.
regards


Pete

1998\10\07@051418 by Regulus Berdin

flavicon
face
Peter Gee wrote:
>
> What would happen in the schematic shown if the input voltage when negative
> with respect to the gnd of the PIC ?
The protections diodes may protect it from damage but excessive current
may destroy it ultimately.

> my guess is that it wouldnt be good for the PIC.
> in a similar project ( from memory), they use a coil, capacitor, signal
> diodes, and a transistor to filter and switch the incoming frequency to make
> it nicer for the PIC to count.
The posted circuit is incomplete, for a more sensitive frequency
counter, it needs a pre-amplifier and convert its output to TTL level.

> i built the project, and it seemed to give accurate results in comparison to
> a bench frequency counter at a frequency of 40Mhz using a 10Mhz 16cf84.  (i
> used an fm RC transmitter to calibrate it) -- i don't have a frequency
> generator higher than that so i can't test its high end response.
The PIC doesn't need to be 10MHz, the input is captured in the RTCC
using it's prescaler which is rated at 50MHz. The pre-scaler cannot be
read directly, that is why RB0 is connected at RA4 to self clock the
pre-scaler to get it's value.  The 470 ohm resistor is to prevent
contention from the input and RB0.

Reggie

1998\10\07@051425 by Regulus Berdin

flavicon
face
Dave VanHorn wrote:
>
> >You can still minimize the parts by having the 7segment common anode,
> >make all the colllectors of the NPN transistors tie to the +5V supply
> >and reverse/invert drive to the LED (to the negative side).  This way
> >the base resistors is not needed anymore.
> >
> >Reggie
>
> Are you SURE they will turn off? Look at the pin specs for minimum
> high output voltage, and leakage current. I've got my doubts about the
> current design, but IIRC, they can drive closer to ground than to VCC.

Yes I'm sure, 25 ma for sinking, V(OL) = 0.6V . I had used this
configuration on some of my designs.

In case you misunderstood my point, here is an ascii schematic of what I
meant.


          O Vdd
          |
          O---------------O---------------O---------------O
          |               |               |               |
          |               |               |               |
        |/              |/              |/              |/
RA0 O---B|      RA1 O---B|      RA2 O---B|      RA2 O---B|
        |\              |\              |\              |\
          V               V               V               V
          |               |               |               |
          O               O               O               O
   digit select 1  digit select 2  digit select 3  digit select 4


RB1 O---/\/\/\-----O Segment A
RB2 O---/\/\/\-----O Segment B
RB3 O---/\/\/\-----O Segment C
RB4 O---/\/\/\-----O Segment D
RB5 O---/\/\/\-----O Segment E
RB6 O---/\/\/\-----O Segment F
RB7 O---/\/\/\-----O Segment G


Reggie

1998\10\07@125210 by Dave VanHorn

flavicon
face
>In case you misunderstood my point, here is an ascii schematic of
what I
>meant.


OK, I got ya. Using NPNs on the top.   That works, you win a bananna.

1998\10\07@130155 by Sean Breheny

face picon face
Hi All,

At 11:38 PM 10/6/98 -0500, you wrote:
>>>The base resistors arent' critical, 470 ohm or 1k should work.
>>
>>Do you really think THAT low? Even if the transistors were completely
>>saturated, I would expect the base resistors to be about 10 times the
>>segment resistors. If we used 470 ohm resistors on the bases, with a
>5V
>>supply, we would have a base current of about 8mA. It would work
>fine, but
>>it would seem to me that for efficiency's sake, a few K would be
>better. It
>>would still throw the  transistors into saturation and save some
>power.
>
>
>You have to allow for all seven segments to be on, plus worstcase of
>the pic output drive..
>A higher R will probably work. I'd use high eff red displays then, and
>do the math. This is an off-the cuff shot.


I must stand corrected. I was tired and not thinking of multiple segments
on at once. Dave, you are right, an R in the 1K range seems correct for
best/most consistent light output.

Thanks,

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
spamBeGoneshb7spamBeGonespamcornell.edu  Phone(USA): (607) 253-0315 ICQ #: 3329174

1998\10\07@182304 by Octavio Nogueira

flavicon
face
>The posted circuit is incomplete, for a more sensitive frequency
>counter, it needs a pre-amplifier and convert its output to TTL level.

Does anyone have a nice and simple pre-amplifier schematic for this kind
of application?

Regards,

Octavio
=======================================================
Octavio Nogueira - TakeThisOuTnogueiraEraseMEspamspam_OUTmandic.com.br ICQ# 19841898
>From the creator of ProPic,   ProPic 2  now much better
*        http://members.tripod.com/ProPic             *
* PIC Programmer for Windows with down to earth price *
=======================================================

1998\10\07@192742 by paulb

flavicon
face
Dave VanHorn wrote:

> OK, I got ya. Using NPNs on the top.   That works, you win a bananna.

 OK, OK.  So where's the *code*?
--
 Cheers,
       Paul B.

1998\10\07@195924 by Regulus Berdin

flavicon
face
"Paul B. Webster VK2BZC" wrote:
>   OK, OK.  So where's the *code*?

Try http://www.picpoint.com .  I had seen it once posted there.

Reggie

1998\10\07@202050 by Regulus Berdin

flavicon
face
Octavio Nogueira wrote:
>
> >The posted circuit is incomplete, for a more sensitive frequency
> >counter, it needs a pre-amplifier and convert its output to TTL level.
>
> Does anyone have a nice and simple pre-amplifier schematic for this kind
> of application?

I'll try on ascii:

                      +---------+---O +5V
                      |         |
                     3K3       1K
                    ohms      ohms
                      |         |
                  +---+         +-----+
                 +|   |         |    +|
            2.2uF =  10K       820    = 2.2uF
                  |  ohms      ohms   |
                 GND  |         |    GND
                      |         |                  OUT
                      |         +-----||----+----O TTL
                      |         |    10nF   |
IN  10nF         10nF  |       |/            |
O----||----+--+---||---+-------|   MPSH10   10K    adjust for DC
          |  |        |       |\           Ohms   level be in the
  1N4148  V  -       3K3        v         trimmer middle of TTL
    X2    -  ^       ohms       |           |     thresholds
          |  |        |         +----+      |
        GND GND      GND        |    |     GND
                               120   |+
                               ohms  = 10nF + 2.2 uF in parallel
                                |    |
                               GND  GND


This circuit could work from to 0.02-50 MHz.

Reggie

1998\10\08@064609 by jmnewp

flavicon
face
how exactly does the pic capture frequencies of up to 50 MHz with only a
4 MHz ocillator?  what is the mechanism?

jon

Regulus Berdin wrote:
{Quote hidden}

1998\10\08@064612 by Dwayne Reid

flavicon
face
PLUS . . . if you tie the collectors of the transistors to the UNREGULATED
supply, the 5V regulator is nice and small and cheap.

>Dave VanHorn wrote:
>> The displays are seven segment common cathode, it looks like a 4 digit
>> multiplexed array, but four singles in paralell would work as well.

>
>You can still minimize the parts by having the 7segment common anode,
>make all the colllectors of the NPN transistors tie to the +5V supply
>and reverse/invert drive to the LED (to the negative side).  This way
>the base resistors is not needed anymore.
>
>Reggie

dwayne


Dwayne Reid   <RemoveMEdwaynerspamTakeThisOuTplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(403) 489-3199 voice     (403) 487-6397 fax

1998\10\08@065651 by Art Goldhammer

picon face
>"Paul B. Webster VK2BZC" wrote:
>>   OK, OK.  So where's the *code*?
>
Try Microchip Application Note AN592. -- ag

1998\10\08@084419 by Art Goldhammer

picon face
>how exactly does the pic capture frequencies of up to 50 MHz with only a
>4 MHz ocillator?  what is the mechanism?
>
The input signal is sent to the prescaler, which is an asynchronous counter.
It can count pulses with 10 ns rise times, which determines the upper freq
limit. Hope this helps. -Art

1998\10\08@132613 by Adriano De Minicis

flavicon
face
>   OK, OK.  So where's the *code*?

http://www.iet.unipi.it/~luigi/pic.html
There is also other PIC stuff here

Adriano

1998\10\08@134813 by paulb

flavicon
face
Dwayne Reid wrote:

> PLUS . . . if you tie the collectors of the transistors to the
> UNREGULATED supply, the 5V regulator is nice and small and cheap.

 Dead right.  Your previous comment to that effect in the July thread
noted :)
--
 Cheers,
       Paul B.

1998\10\08@135529 by Bob Blick

face
flavicon
face
If anyone wants the English version of the text file for this project let
me know, I can email it out tonight. Please respond to me, rather than the
list, so your request will stick out from the rest of the piclist
messages.

It's rather big, so I won't send it to the list in general.

-Bob

1998\10\08@145158 by paulb

flavicon
face
Regulus Berdin wrote:

> Try http://www.picpoint.com .  I had seen it once posted there.

 You're right!  Apparently so had I, as I already had it on file!  Boy
I must start looking through my 500MB of files!

 This one I must build for interest, but I'm fancy doing those little
optimisations on the drivers!
--
 Cheers,
       Paul B.

1998\10\09@015500 by Norayr S. Elmayan

flavicon
I don't know if this was discussed before, my question to you is resolution
at 4.0 Mhz.  If I were to display decimal frequency in the range of 0 to
120 Hz, the max resolution I can achieve is per bit 0.48 Hz.  It means if I
were to display a decimal point, each display advancement is 0.48Hz.  Is
there a way to improve this.

Norayr

1998\10\09@025344 by Regulus Berdin

flavicon
face
"Norayr S. Elmayan" wrote:
>
> I don't know if this was discussed before, my question to you is resolution
> at 4.0 Mhz.  If I were to display decimal frequency in the range of 0 to
> 120 Hz, the max resolution I can achieve is per bit 0.48 Hz.  It means if I
> were to display a decimal point, each display advancement is 0.48Hz.  Is
> there a way to improve this.

You can improve the resolution by increasing the capture time.  A 1
second capture time can give you 1 Hz resolution and 10 seconds will
give 0.1 Hz.

But I think you misunderstood how the system works, the count range is
not only 8 bit.  The minimal range is 16 bits and can be expanded by
polling the TMR0 overflows which is easy because it will only occur at
minimum every 1/760 second.

The frequency is read via RA4/TMR0 which a pre-scaler/divider is set in
between the TMR0 register.  Reading the TMR0 for each second or a fixed
period, will give you the frequency per time period divided by the
prescaler value.  To make it simple, the prescaler is set to 256
divisions, so the TMR0 can be the high byte of the 16 bit number.
Reading the pre-scaler is tricky because it is not mapped as a
register.  The trick is self clocking, RB0 is connected to RA4 and is
clocked until TMR0 changes.  The value of the pre-scaler will be 256 -
no. of clock pulses.

I hope this answers your question.

Reggie

1998\10\09@073028 by vk7krj

flavicon
face
Hi Bob, I would like the english translation please. Thanks for taking the
time to do this for everyone.


Cheers, Ken
vk7krjEraseMEspam.....southcom.com.au

1998\10\09@174106 by John de Stigter

flavicon
face
Put me down for a copy.
Regards,
John.

----------
> From: Bob Blick <EraseMEbobspamTED.NET>
> To: RemoveMEPICLISTEraseMEspamEraseMEMITVMA.MIT.EDU
> Subject: Re: 4 digit auto-ranging frequency-meter.
> Date: Friday, 9 October 1998 3:44
>
> If anyone wants the English version of the text file for this project let
> me know, I can email it out tonight. Please respond to me, rather than
the
> list, so your request will stick out from the rest of the piclist
> messages.
>
> It's rather big, so I won't send it to the list in general.
>
> -Bob

1998\10\09@180822 by paulb

flavicon
face
John de Stigter (and many others) wrote:

> Put me down for a copy.

 Might be as well to simply web-page it?
--
 Cheers,
       Paul B.

1998\10\09@185804 by Bob Blick

face
flavicon
face
On Sat, 10 Oct 1998, Paul B. Webster VK2BZC wrote:
>
>   Might be as well to simply web-page it?

Yes, I think that's probably what I'll do, since I have 15 requests in my
inbox. When I get home tonight I'll put it up and post the URL.

-Bob

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