This project was started roughly 8 years ago when the large Boroughs B-7971 nixie tubes were still reasonably priced. My friend scored these six tubes on eBay for $10/ea. These particular tubes were salvaged from the ticker boards of the New York stock exchange. The clock uses an older Atmel AVR 90S2331 microcontroller as a CPU. The code was written in bascom also by my friend after a two-year setback where my wife moved the clock while it was only half assembled and fried the first Atmel chip. I originally modified my friend’s code in RVK but he decided to gut the code and rewrite it by the time we got around to revisiting this project. I built the case out of 1/4″ oak that is obviously stained black. There are no nails in it. It was done entirely with wood glue and clamps since that’s what I had at the time I started the project.
My friend James painstakingly built the entire circuit on perf board for me. The tubes are driven directly from 12 TD62084AP 8 channel high voltage driver ICs which are in turn driven by an array of 12 cascaded 74HC595N shift registers. Other than that, there is a beefy power supply that puts out the 170v and some lower voltages for the logic circuitry. It uses the 60Hz of the A/C line for a sync source.
I’m very pleased with how the final clock turned out. It seems to keep the time very well.
