Thirty-one tubes to tell the time, and as a glowbug fan I’m not even mad.
Charles van Den built it with no silicon in the electronics, and his Hackaday.io page says why:
I wanted to do something where the dekatron was used for its original purpose, to count things
That’s the right instinct, and I’d have built it the same way. He takes the second from the wall:
The 1Hz frequency is derived from the mains frequency (50/60Hz).
Smart, since the grid already counts cycles better than a pile of tubes would. In the photo the tubes glow orange on a polished aluminium plate, and one has a numbered ring around its base, which is how you tell a counter from a light bulb.
but it is not something to turn on 24×7!
Of course it isn’t. The page says it draws a little over 80 W, mainly filaments, so my math says 1.9 kWh a day (about 58 kWh a month) to show 0:00 to 11:59, and the tubes get a little over a year of life. I’ll say it: eighty watts for a clock face is a lot. It’s also the price of a counter you can see working, and I’d pay it over a chip I can’t see.
Can you build one? The page has a KiCad schematic, a FreeCAD file for the front plate and a 23-line parts list, but no repo. Heed the maker: he wired it point to point and says he regrets that, and he says R43 in the schematic should connect to the 200 V supply. About the GS12C dekatron he writes:
I guess this thing is hard to get.
His October 2025 log says the tens-of-minutes dekatron “sometimes seems to miss a step”, and I can’t stop wondering whether a 12-step tube running on only six outputs has anything to do with it.