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Breaking the price barrier: An autoranging frequency counter with RS232 output

I found a nice auto ranging frequency counter online here:

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Did not have those 7 segment displays, considered an LCD interface, but why not use RS232, and power it from the RS232 too? Just a probe you can bring along with your laptop, saves weight :-) So.. modified that code a bit:-)

This is what the output looks like: ftp://panteltje.com/pub/RS232_frequency_counter_output_on_monitor_img_1515.jpg

When it is measuring it's own crystal (20MHz): ftp://panteltje.com/pub/RS232_frequency_counter_img_1513.jpg

This is how simple it is, only 7 components, not counting some input FET: ftp://panteltje.com/pub/RS232_frequency_counter_diagram_img_1516.jpg

This is the modified asm source for a PIC 16F648A: ftp://panteltje.com/pub/counter-0.1.asm Could not get it in a 628, wanted to leave the original 7 segment code in too. Will have a go later perhaps to see if I can eliminate those few bytes over 2 k.

Resolution is 1 kHz on the MHz range, and 1 Hz on the kHz range. The crystal will need a trimmer to set it to exact frequency, used 2 x 22 pF here.

Oh, yes, that is a PIC. Total cost, without input FET... maybe 10 $? This could fit in a D connector shell, and have a pin stick out of it to measure with.

Reply to
Jan Panteltje
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Made a web page for this project:

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The latest asm source and info will be here.

Reply to
Jan Panteltje

here.

measure with.

Heres one with the LCD display

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It uses 877A which is a bit overkill. You have to give an email to get the source code. I have it if you want?

If you find a PIC based esr meter with LCD display let me know. I've found a couple but nothing intresting yet.

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Reply to
Hammy

Here's some prescalers for that...

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Cheers

Reply to
Martin Riddle

I enjoyed this pair of comments:

"The prescaler described here connects to the front end of a 100-MHz frequency counter..."

and,

"The prescaler has some limitations. Its lower frequency limit is about 200 MHz."

Could be a problem area here, for some.

Jon

Reply to
Jon Kirwan

On a sunny day (Sat, 29 Aug 2009 19:42:53 -0400) it happened Hammy wrote in :

I have the LCD code, wrote it for some other PIC projects:

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That LCD driver is mainly Microchip example code really.

It relatively easy to stick that LCD driver onto any project.

Nice. ESR of 22 pF caps?

I do not normally measure ESR, I just [diff] scope over the cap, if I see fast rise times it is defective :-)

Reply to
Jan Panteltje

On a sunny day (Sat, 29 Aug 2009 22:29:36 -0400) it happened "Martin Riddle" wrote in :

Nice and small, first time I heard the expression 'DX shipping'.

Can finnaly check the frequency of the microwave oven.... hehe

Reply to
Jan Panteltje

ftp://panteltje.com/pub/RS232_frequency_counter_output_on_monitor_img_1515.jpg

Ha ha, I was thinking WiFi.

Cheers

Reply to
Martin Riddle

At what frequency?

--
You can\'t have a sense of humor, if you have no sense!
Reply to
Michael A. Terrell

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