Frequency Counter (5Mhz) using PIC16F72 and an Opamp Schmitt Trigger ...

[itzvinodh]

This frequency meter is capable of frequencies upto 5Mhz . It has an error rate of 5% at any frequency. (by averaging ..)

The compiler used is HI-TECH C . (basically the program can be recompiled for any PIC which has a CCP1 module and timer 1).
Xtal is 20 MHz.
The opamp can be any model that has GBP of about 20Mhz.

The circuit can directly measure any frequency upto 4.5 - 5 Mhz.

( The frequency range of this counter can be increased upto 10 to 20MHz, by adding a frequency divider circuit. )

The files can be downloaded from
Hotfile.com: ?atwy hosting plików jednym klikni?ciem: freqcntr.zip


Check it out and suggest improvements if any This is my own successful project . mi8 b able to help in your doubts if ne.
Hava Nice Time

 

[ALERTLINKS]

Link is not properly inserted.

 

[milind.a.kulkarni]

Yes ....I also don't found link is working...

 

[itzvinodh]

Well... Got the link working... Check it out now...

 

[milind.a.kulkarni]

Can u Please mention name / part number of the IC like Opam like ua741 and LCD like LCD-016M002B in the schematic will be helpful to may of us.... Also, I found capacitor missing for oscillator

Nice share... and thanks for such good design....

regards

 

[itzvinodh]

The Opamp (is used only as a Schmitt Trigger) can be any part that works above 5Mhz .... I have an updated design using a schmitt trigger (74HC14)... it will be easier and much cheaper than the opamp version i guess...

As for the Capacitor values it should be 15pF .... (but its a non critical as specified in the datasheet of pic16f72). I didnt use it in my hardware circuit and it just worked well...

The Display is a JHD162A (16x2 Character LCD) actually any HD44780 based Char LCD must work.

The updated schemetic file is at....
Hotfile.com: ?atwy hosting plików jednym klikni?ciem: Freqcntr.PDF

---------- Post added at 16:22 ---------- Previous post was at 16:09 ----------

if you use an opamp its OPA2322. (BURRBROWN costs around Rs 200 ) ....

So, better option would be to use a 74HC14 which is a Hex(has 6 inverter modules) Inverting Schmitt Trigger... It would be well around Rs 20 to 30... within our budget i guess ...

The model has been simulated in Labview Proteus and has been also been implemented in hardware...
Labview Proteus shows an error in reading of 2% (such errors are pointless in real life..) Still im trying on a new averaging feature which would reduce the errors, Would be uploading the code if successful (also planning to add a LC meter function to the same circuit ).

The Coding is done to perform the job and does no fancy stuff like showing the readings in Mhz / KHz , decimal points etc...
It simply shows the reading in Hz...

 

[mvs sarma]

there are counter design that work well beyond 30MHz. they use PIC16F628A, and a single transistor in the front signal conditioning.

for example, check Ham Radio And Electronics Website :: HamRadioIndia

once you can add a prescaler like SAB6456, you can reach V/UHF ranges.

 

[itzvinodh]

@ mvs sarma

Aktually the pic directly cannot reach a frequency like 30 Mhz since the 18F models themselves are upto 12MIPS only...
so it doesnt matter whether it is PIC16F628A or PIC16F72 greatly...

Depends on the prescaler... thats the reason i said adding a frequency divider circuit could greatly increase its range...

My main concern is the cost nd complexity since its just a hobbist project...
Thanks for the advice on using the SAB6456 as the prescaler would test it on proteus vsm simulator first

 

[mvs sarma]

i have working unit with me. please study the link i have indicated. perhaps i can make .asm available if needed for examination.

 

[betwixt]

The PIC timer input will work MUCH faster than instruction speeds. You dont have to poll the pin to check it's state, it connects directly to the internal timer circuits. It's quite common for 4MHz clocked PICs to count pulses at up to 50MHz.

Brian.

 

[mvs sarma]

Yes. This should motivate the O P who could plan for reaching higher count while using 16F72 itself.

 

[itzvinodh]

Thanks MVS SARMA..
Am trying with the timer 0 and prescaler lik the ham radio people just did...
i am not that good in assembly... so have to start from scarp in C...

 

[ALERTLINKS]

This frequency counter is around about 20 years old. The original version(i guess) was made with PIC16C54 printed in an electronics magazine as a constructional project. I have that issue. It appeared on internet with modifications and improvements.
Frequency Counter,PIC 16F84,Weeder Technologies
PIC 16F628 Frequency Counter with RS232 output in a DB9 backshell by Jan Panteltje

**broken link removed**
Frequency counter with PIC and 4- to 5-digit LED display
http://www.qrpproject.de/Media/pdf/DL4YHFcounterEnglManual.pdf
Microchip website has an application note AN592 of a frequency counter using PIC16C54,
**broken link removed**
Using c, 50MHz.
A PIC frequency counter project written in C using TMR1 and an LCD.
And
OM3CPH home page
OM3CPH home page

 

[hcl8612]

use the IC MB506,the max frequency can be reached to 2.4GHz