Nixie frequency counter gone timepiece

nixie clock hack

[Windell] of Evil Mad Scientist Laboratories took an ancient Nixie tube based frequency counter and converted it into a clock. The unit he got his hands on is an HP model that was still in great shape. He’s using an internally generated one second pulse as the clock signal, but some modifications are necessary to display time. That’s because the frequency counter is base 10 and clocks use a quirky combination of base 60 and base 12.

It wasn’t too much of a problem to rig up a system to track minutes and seconds. The tens digit for each is monitored by a couple of AND gates that he added to the mix. When they detect a ‘6’ the digit is reset and a pulse increments the next digit as the carry. This is more difficult to accomplish with the hours though. Minutes and seconds count from 0 to 59 but hours don’t start at 0. Instead of over-complicating the logic [Windell] used a bit of slight-of-hand. The Nixie tubes for the hours have been rewired so that when the counter is at 0, the filament in the shape of a 1 lights up. No difference in logic, just a translation that makes them display one digit higher than the actual count.


  1. biozz says:

    damn people are turning these things in to clocks when im spending at least an hour a day on ebay looking to buy a working one cheap >_>

    if you have an old counter, generator, scope or anything like that you wanna rid of email me at … sorry to advertise im desperate XD

  2. dAN says:

    Agreed, what was wrong with having a nixie tube frequency counter? Way more useful than a clock IMO.

  3. Kalleguld says:

    “Minutes and seconds count from 0 to 59 but hours don’t start at 0.”

    Yeah they do – oh, you are still using the archaic 12-hour system where hours don’t reset at the same time as am/pm or dates.

  4. matt says:

    Projects like this are great for people who want to make a nixie clock but aren’t comfortable messing with high-voltage power supplies. I turned a busted one into a clock last year and it’s still on my desk, ticking away.

    Wasn’t there some guy who turned an unmodified frequency counter into a clock by feeding it exactly the right amount of high-speed pulses to make the display show the time? I think I saw that a couple years ago but I don’t have a link. Ingenious idea though.

  5. alankilian says:

    biozz, I sent you a message about a signal generator and an oscilloscope you can have for shipping.

  6. medix says:

    @matt: I believe that was also a work of cleverness. Any time there was a rollover, the entire counter was reset and clocked back to the correct ‘time’ value, but so fast that POV takes over and you only see one update.

    I think that’s how it went anyway. Can’t remember what the update time was like though.

  7. Jakezilla says:

    @matt You don’t need a HV supply, just a driver chip like the 7441 or similar solution. You will still have HV on your board, but it is very low current.

    Is there a site for buy/sell/trade used instruments? I would love to get a decent 4 channel oscilloscope. All I can find is either high quality calibrated used equipment that costs $$$$ or old phosphor scopes…

  8. Squirrel says:

    So judging by the comments so far, I think HaD needs to have some type of marketplace…

  9. polossatik says:

    lol.. hours don’t start at 0

    So I live in a place without time for one hour of the 24 hours? :)

  10. zool says:

    @Squirrel, HaD fleamarket?

  11. bearmos says:

    “clocks use a quirky combination of base 60 and base 12.”

    The digits of a clock are still base 10 (each digit represents one of 10 values). . .that is, of course, unless you’ve got a binary or hexadecimal clock!

  12. Kees Reuzelaar says:

    I would gladly have shipped three nixie clocks and complete parts for another three for free to the “hacker” in exchange for this counter.

    Barbarian… :-(

  13. s says:

    Don’t know if it would be workable, but HaD fleamarket would be great.

  14. leadacid says:

    @Squirrel, zool, s
    I’d love a good trade/loan system or forum. I’ve got some equipment that I’ve picked up and only used for one or two projects but otherwise sits on a shelf. I grabbed a good 1980’s HP 1630 series logic analyzer that I used for one project and now it sits waiting for another purpose.

  15. Hitek146 says:


  16. Fallen says:

    I would find a trading post very useful.

  17. nave.notnilc says:

    I’d suggest you add some capability for local trading, easier to trade random bits if you don’t have to do shipping, and you get the plus of meeting other enthusiasts

    gotta make it more useful than ebay in some manner :P

  18. HackerK says:

    What a waste to a freq counter! First thing come to my mind would be using uC to generate the exact freq to have time display on a freq counter…

  19. Paul says:

    I think it’s a shame to destroy a perfectly working almost antique high quality HP lab equipment into the 100.000nth nixie clock.

    It would have been a nice hack though if it was done without any modification to the frequency counter.

    It wouldn’t even have been very difficult to do so. You’d only have to generate som “odd” frequencies.

    “Look ma, I turned that stupid flatscreen television you bought last month for $4500 into a very nice psychedelic disco light. And I only had to short circuit these 3 little black thingies”

  20. Paul says:

    To add something positive to my previous negative post:

    A guy named Jesper made some software for an AVR to do software DDS.

    Generates frequencies up to 300kHz with a resolution of 0.07Hz. Which is good enough for a clock like this.

    Here is his site:

  21. Scott says:

    What a waste of a frequency counter. Someone should buy an airplane, take off the wings, keep the wheels, and “hack” it to make it a car.

  22. Whatnot says:

    Yep, I agree, frequency counter beats clock.

  23. Baba says:

    I hate that all of this great old test equipment is getting turned into clocks. Vintage oscilloscopes, frequency counters, and voltmeters are fun to use and much more expensive/rare than clocks.

    It might have been neat if he had built something he could plug into the frequency counter which would generate frequencies that could display the time. I wouldn’t have been that much more difficult, it wouldn’t have destroyed the frequency counter, and it would have been portable to every other frequency counter ever made. Someone needs to do that.

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