Very Simple PC Frequency Counter Works Up To 100MHz

We all use 74 logic in our projects as general purpose logic interfacing glue. These chips have become as ubiquitous as a general-purpose op-amp, or even as passive components. In most cases we’re not demanding much of them, and power requirements aside an original 74 chip from the dawn of the series could probably do the same job that we’re putting a more modern variant to work on.

It is easy therefore to forget that 74 logic is a field that has seen continuous improvement and innovation reflecting the developments elsewhere in electronics, and the most modern 74 versions hide some impressively high specifications.

A good example comes via a project from [Scott, AJ4VD], a very simple frequency counter that uses a single 74 series chip at its business end, and counts to over 100MHz. The chip in question is a 74LV8154 dual 16-bit counter which he is using as a prescaler to deliver a rate more acceptable to an ATMega328 microcontroller that does the counting. As he points out, the accuracy of a frequency counter is only as good as its gate timing, and he ensures as accurate a seconds-worth of pulses as he can with a 1PPS signal derived from an inexpensive GPS receiver. The 328 makes its counting available to a host computer via a serial port, and can be easily read through a terminal. He’s built it dead-bug style on a piece of unetched PCB, on which the simplicity of the circuit is evident.

There was a time when a project like this one would have required multiple integrated circuits including a probably quite expensive purpose-built prescaler. Cheap glue logic has now advanced to a stage at which it can be done instead at commodity prices, and we like that.

We’ve featured a few 74-series counters before, including this old-school one and this one also using a 74LV8154.

Frequency counter for $10 worth of parts

[Scott] built this frequency counter using less than $10 in parts. It’s set up to meter frequencies in megahertz which is fitting since he’s planning to use it with his radio hardware experimentation. But we would find it useful too because our cheap multimeter only reads up to around 4 MHz.

He’s using an ATmega16 that he had on hand but it has features way beyond the specs for the device. He speculates that an ATtiny2313 would easily work in its place. The microcontroller is mostly used to drive the multiplexed 7-segment display after reading the frequency values from the 74LV8154 counter chip that he is using. He doesn’t have a full schematic for the device, but there is a hand drawn diagram for using the frequency counter; the rest should be easy to piece together. Looking at that circuit we don’t think it would be too hard to make this a manual-ranging frequency counter to give you more use out of the dedicated device. Check out [Scott’s] demonstration video which is embedded below the fold.

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