Easy Frequency Counter Looks Good, Reads To 6.5 MHz

We were struck by how attractive [mircemk’s] Arduino-based frequency counter looks. It also is a reasonably simple build. It can count up to 6.5 MHz which isn’t that much, but there’s a lot you can do even with that limitation.

The LED display is decidedly retro. Inside a very modern Arduino Nano does most of the work. There is a simple shaping circuit to improve the response to irregular-shaped input waveforms. We’d have probably used a single op-amp as a zero-crossing detector. Admittedly, that’s a bit more complex, but not much more and it should give better results.

There was a time when a display like this would have meant some time wiring, but with cheap Max 7219 board available, it is easy to add a display like this to nearly anything. An SPI interface takes a few wires and all the hard work and wiring is done on the module.

The code is short and sweet. There are fewer than 30 lines of code thanks to LED drivers and a frequency counter component borrowed from GitHub.

If you add a bit more hardware, 100 MHz is an easy target. There are at least three methods commonly used to measure frequency. Each has its pros and cons.

12 thoughts on “Easy Frequency Counter Looks Good, Reads To 6.5 MHz

  1. Lacking schematic, but at least a bit of HP and afterwards LP filtering along with limited input protection (not that many of his targeted readers are likely to identify those components).

    1. It’s up to 15GHz due to limitation of bandwidth of the first prescaler. Also I don’t think the physical construction would permit it to work reliably at that frequency. I’d say the problems might start around 3-5GHz…

      1. Yeah you may be right, I just parroted their title. But even 15 GHz would be a nice boost over 6.5 MHz! To get that high in frequency with small signals the input is going to be bare naked though; little (if anything) in the way of protection.

        [Mircemk] could push his 6.5 MHz box to ~40 MHz by addind a 74LVXXX counter as a prescaler (SN74LV8154 maybe?)

  2. I’m not sure why anyone would actually want to mimic this, given the extremely low upper frequency limit and total lack of a even half-respectable oscillator… Can we say error? Lmao
    There are thousands of better frequency counter projects out there for all of you makers to mimic.

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