[Reboots] is a humble hacker who enjoys nixie tubes. So when he saw an old General Electric battery charger for sale at a hamfest, he thought: “that case would make a nice clock…”
He was first exposed to nixie tube clocks a few years ago when his brother gave him a DIY nixie clock kit from [Peter Jensen's] website TubeClock.com — it was an easy build, and worked very well. It also introduced him to a unique driver for nixie tubes, an HV5622 high-voltage shift register made by Supertex inc. Compared to the traditional (and rare) 74141 nixie driver chips or discrete transistor drivers, the HV5622 is much smaller, requires less microcontroller I/O’s, and is not as picky when it comes to powering it.
The nixie tubes he chose for the project came from a lot sale on eBay, Russian surplus IN-12 tubes. He even managed to find an english datasheet for them!
Having decided on the nixie tube, driver, and case, he now needed a reliable power supply. Threeneuron’s design fit the bill nicely, however it ended up being a bit noisy under load, but [Reboots] notes that the TubeClock kit used a free-running transistor oscillator, which was in fact even louder under load!
From there it was a matter of testing the tubes, prototyping some PCBs, and programming the ATmega48. Simple, right? Nixie’s are never that simple. But lucky for us, [Reboots] has an amazing build write up on his site, so if you’re interested in learning more, take a look!
Oh, and if you’re looking for a really unique nixie clock — why not build one without a PCB entirely? Just don’t touch the high voltage lines…