Electronics > PCB/EDA/CAD

Dave's Frequency Counter

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Sparky49:
Well, there are lots of good projects there! :/

One quick question about this frequency counter, what is the divider input/output exactly? Is it all included on the PCB?

I see that you don't have any extra information on the circuit, but if you could help me, I'd really appreciate it. :)

http://www.alternatezone.com/electronics/freq.htm

Sparky

poodyp:
I believe the divider is meant to be switched in on the input to divide the input by 1000 to give a 1Khz to  range.

The way it works, from what I can tell, is the 4553s count the number of pulses on their clock pin. IC5 will count to 999, and when it overflows pulses OFV to IC4. IC2 basically generates 1pps, and the 4553s take the stored number and outputs them to the 4511 BCD decoders. I have no idea why all the filters and nand gates are needed for though, other than inverting.

I think I might have to throw one of these together too.

EEVblog:
I'll scan the Silicon Chip article for it.
I can't find the original article text anywhere  :-[

Dave.

PA0PBZ:
My guess is as follows: The 4521 outputs a 50% duty cycle 0.5Hz square wave, of which half (1 second) is used to enable the counter (DIS on IC4/5, so technically 'not disable'). Shortly after that IC3A gives a pulse to transfer the count to the output of IC4/5 (LE). Then a while after that (hence the 2 ports as a delay) IC3C resets the counters (MR). Then it starts all over again...

poodyp:
Ah, I see. The filters and nand gates turn the square wave into pulses for the reset, and act as a pull up for the LE. For some reason I was thinking the 4521 was already a pulse and not a square wave. Check out the simulation. I'm going to try recreating this as a single board with surface mount components.

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