Pint-sized Nixie display fits neatly in your pocket

[Brett] has had Nixie tubes on the brain ever since being introduced to them by a good friend of his. He decided that building a Nixie-based key chain would be the best way to familiarize himself with the technology, while also giving him a project to enter in the 555 Design Contest. He dug up the smallest Nixie tube he could find that displayed digits, and got down to business.

The biggest obstacle he ran into was figuring out how he would provide the high voltage required to light the Nixie tube. He eventually built a transformer circuit driven by a 555 timer, using a small 12v battery as his power source. Once everything was up and running on a breadboard, he designed and etched some PCBs, then soldered everything together.

The end result is a nifty little key chain that flashes the number 5 when a button is pressed – pretty appropriate for the 555 contest. It’s a great looking project, though we’re still not 100% sure what we think about a naked high voltage circuit residing in our pocket.

Keep reading for a pair of videos documenting the key chain’s construction and operation.

Comments

  1. Jason says:

    Looks awesome dude! Great work i hope you win the contest.

  2. Tim says:

    I loove nixie tube projects. Im surprised he didnt just have the 555 count 0 to 9. Seems a little overly complicated to just have it flash 5 over and over.

  3. Hi Tim, thanks for the support. Nixie tubes are really neat, and I hope you got to see the video… I did a really cool macro shot of the tube. It actually flashes “5 5 5″ with a pause and then repeats. I suppose I could have done a sequential counter, but then lots of logic would have been placed into the hands of a counter IC. I had a bunch of SMT 555’s and some space on the bottom of the PCB, so it seemed natural to do what I did ;-) Version 2.0 is going to have a microcontroller and will be able to control all of the digits, with PWM’able digit fade.

  4. zool says:

    cool, nice job on the blinking part and the transistors

    i think there are smaller smd transformers you could use…
    also needs some kind of case

  5. Frogz says:

    it flashes 555 instead of 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 12:00 (for added laugh, i just typed this, not pasted)

  6. @Zool, thank you! I did find a smaller SMT transformer but as I mentioned in my blog post my parts arrived WAY too late to add it to the PCB. I have it now though and will be working on making it even smaller and more functional.

    @Frogz, yes it’s kind of like the clock you “can’t set” right now ;-)

  7. Nick Short says:

    I don’t think that the naked high voltage would be a problem.

    He used a transformer to step up the voltage from the 12v battery. We all know that when you step up the voltage, the current goes down.

    The level it would end up being is really small, so wouldn’t that drop the high voltage off sharply if your hand drew more than a couple dozen microamps?

  8. EMG says:

    The high voltage shouldn’t be that big of a deal as the energy contained in that 12v cell shouldn’t be enough to give high current at high voltage. Just don’t wire it directly across your heart/brain

  9. Actually guys, the high voltage output is plenty capable of delivering a couple milliamps of current without folding back (voltage dropping). I’ve accidentally bumped into it already while it was on the breadboard and it made my hand numb for about 20 seconds thereafter. Let’s just say it’s NOT pleasant ;-) I entered this into the Art and Minimalistic categories, and was actually thinking of adding a two-prong tazer style attachment that would make the device very Utilitarian as well. Oh well, I’d rather it have a “safe” reputation anyway.

  10. strider_mt2k says:

    I can imagine it now…

    “All I remember is them repeatedly shocking me, and the number 5, over and over again!”

  11. strider_mt2k says:

    Oh yeah, and this:

  12. Hahahaha! Thanks a lot! Now I’m going to have that song in my head all day!!

  13. Doug says:

    @ Nick Short; No I didn’t know increasing the voltage output of a power supply decreases the current output of the power supply. Because it simply doesn’t work that way. Increasing the voltage can mean less current is needed to provide an equal amount of power though. comparing apples to oranges could hurt unexpectedly.

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