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.

Comments

  1. Chris Muncy says:

    Very nice!
    This would be perfect for using as a readout on a VFO, re like my Kenwood TS-520.

    Thanks for sharing.

  2. Scott says:

    Haha wow I never even thought of adapting this for a
    digital readout for an old rig. What a cool application! It should be trivial to do too…

    My original plan was to use this as the readout for some homebrew transmitters/receivers I’m working on. I wanted a device that would be cheap and easy to replicate that I could slap into RF projects as I make them. … but I like the idea of adapting them to older commercial rigs as well. I have a TenTec Century 21 (what a classic radio!) that would LOVE a digital readout like this…

  3. Chris Muncy says:

    IIRC on my 520 there is an IF out on the back that you could use to trigger the counter. Then all you’d need to do is add your multiplier and bada boom bada bing!

    Have you figured out how high you can read with what you have? I imaging that you would need some isolation and some interstage shielding if you really wanted to get higher in freq.

  4. Oren Beck says:

    VERY good work to do this so affordably. and it was done well in all other respects.

    Be very careful with what you connect and how -to those IF ports. IIRC several of them were not too buffered internally. If a radio’s “Pre-Digital” be even more careful. If it’s a Transceiver, the RF field coming back in can be not fun to diagnose.

    Ferrites are your friend..Same with shielded cables having multiple braids like Triax. “signal and signal ground runs on center conductor/innermost braid, Outermost braid is chassis ground, being wary of Ground Loops.

    Let’s just say- Having built repeaters from used cab radios etc teaches how grim it gets if we overlook such design elements. 99 out of a hundred work on any coax or even zip cord in some RX only setups. That one build that tolerances stack against us can be so exasperating as to defy description. I’d also consider some screen mesh across the display if you cannot kill hash noises any other way. Placing a cheap AM radio near older “non-radio” LED clocks demonstrates the reason for my comments. Look at scan rate harmonics Vs that IF freq:>

  5. Chris Muncy says:

    Now Oren you bring back some good old memories. Motorola Micors and turning them into repeaters. And yes on the ferrite beads!

  6. Murray says:

    Nice. For an even cheaper option check out http://opend.co.za/hardware/freqmeter1/index.htm
    90 mhz, a 4060, 3 resistors, 3 capacitors and 2 diodes.
    Murray.

  7. Scott says:

    @Murray I like the link! Very clever! $2 in parts plus $200 for a PC lol

    @Ekaj You caught me! This device measures and displays frequency of an AC signal, as others have done in the past. I’m a copycat! Dang, I almost got away with it too ;)

    Similar hackaday posts worth glancing at:
    http://hackaday.com/tag/nixie-tube/ (an actual frequency counter gutted and turned into a clock)
    http://hackaday.com/2007/07/29/diy-frequency-meter/ (DIY, 500kHz max)

  8. Very nice project Scott! I used those RCA connectors on just about all of my early projects. They are cheap, easy to mount and I had tons of cables already :) Plus they are actually good for keyed applications, i.e., you won’t be plugging in your laptop power supply to one of them accidentally. Keep up the good work, and try to build and scavenge whatever you can, and then when you get the money buy better stuff and your skills will improve 10 fold.

  9. Jaton says:

    How would one get it to sample frequencies up into the gigahertz range?

  10. @Jaton – you need some high speed Flip-Flops to divide the signal down to something your microcontroller can measure.

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