After watching a recent Technology Connections video about Numitron tubes, I was inspired to pick some up to add to my dragon’s hoard of junk. A quick visit to eBay later, and a few less dollars in my bank account, and I had some new-old-stock tubes in hand.
At first I wasn’t sure what I wanted to use them for, so the obvious answer is a clock. I did decide, that if I was going to make *yet another* clock, it was going to be a very nice one.
Starting with the electronics, I put together a board using an ESP32, some shift registers and driver transistors, and a Real-Time Clock chip with battery backup to keep time even when the clock is unplugged.
A little bit of bad Arduino code later, and we have a functional clock, with 12/24hr modes, three brightness levels (done with PWM), and calibration methods so I can calibrate the cheap quartz crystal on the board against something better, like a GPSDO or my Rubidium standard. It won’t really be that accurate over the long term, but I can calibrate out enough error that you’ll never notice the clock being wrong before you have to re-set it again anyway next time daylight savings rolls around to give everyone the big middle finger.
Next was to figure out a case for it. Obviously 3D printing would be an option, I thought about laser cut acrylic as well, but I didn’t think it really made for a polished enough end product, and the overall look seemed off to me. So I get to pretend like I’m a woodworker, and ordered some small blocks of maple and redwood (from already fallen trees) from a specialty wood supplier.
And just like a TV cooking show, through the magic of a million hours of cutting, sanding, chiseling, gluing, finishing, and self-loathing that we’re not going to show you, it’s done!
I’m really happy with both of them. The redwood and the maple both have some really appealing characteristics. I ended up keeping the maple one for myself, and giving the redwood one to my dad for the holidays. He displays his with a quartz crystal he was also gifted this year.
