Frequency Comparator Circuit using flip flops and counters

[VATSAL1811]

Hi I need to design a frequency comparator that compares frequencies between 1Khz and 15 Khz,
I have Flips-flops, 7493 counters, Comparator and gates.

 

[d123]

Maybe you understand how to modify #3 for your needs, or #2:

**broken link removed**

Good luck!

 

[chuckey]

The first thing to do is to amplify and limit the incoming signalls so they are logic levels square waves. Then there are a couple of ways to proceed, analogue or digital.
The analogue way woulld be to use one edge of each square wave to transfer a known amount of charge, either by using two differentiators or a monostables. Then invert one and integrate the difference. So the faster signal side accumalates more voltage the then slower signal. So use this difference in voltage to drive your F1> F2 LED.
The digital way would be to have a low frequency reset signal and two counter chains. So the reset sets both counter chains to zero. With two different input frequencies each counter would count up at a different speed. use gates to determine which counter is counting faster, say by comparing the 4th output. Use this to reset the counters and light the F1> F2 LED.
Frank