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Frequency Counter

Frequency Counter

The device presented here can be used to count events as well as to measure frequencies and times. Most of it is built from discrete HC (high speed CMOS) logic.

Frequency measurement from 0.1Hz to ¡Ý10MHz; gate times of 0.1, 1 and 10 seconds.

Time measurement 0.001ms to 10000s (time clock 1MHz and 1kHz): measuring L/H time or 1, 10 or 100 complete pulses or time between input A and B transition.

5-digit LED display with display hold.


CMOS-compatible Schmitt-trigger inputs with over- and under-voltage protection.

The circuit is divided into 8 separete module sheets (with the top ones in the list below being more interesting) and one connection diagram on how to put the modules together.

Connection diagram: How to join the below modules.

Input schematic: The discrete “heart” (trigger,…)

Logic schematic: The micrcontroller and the supply circuit.

Divider schematic: Divide frequencies by 1,10,100.

Oscillator schematic: 1MHz and 1kHz clock source.

Counter schematic: 5 digit 7-segment LED counter.

BNC input schematic: CMOS compatible input with protection.

“Hardware keys”: 4 debounced keys.

Front panel schematic: Added here for completeness.

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