Nixie tubes have been around since the 1950s, but haven’t been manufactured in significant quantities since the ‘90s due to newer display technologies rendering them obsolete. Now they’re used almost exclusively by makers who appreciate their unique aesthetic. The glowing numbers have a cyberpunk appeal that is hard to ignore and makes them ideal for stylish clock designs. But Nixie tubes require unique power and control requirements that tend to make them bulky. That’s why it’s so impressive that Instructables user RemcoK3 was able to build a wristwatch with tiny Nixie tubes.
RemcoK3 is an electronics engineering student, and started this project off a little too ambitiously. Their original design featured four individual Nixie tubes. Those got their juice from a battery through a power supply that pushed the 4.2V all the way up to the 170V that the Nixie tubes require. Control was provided by an ESP32 module, which allowed for some internet capabilities. That design did work, but it was too big to be a practical wristwatch once it was enclosed in a 3D-printed case. RemcoK3 was forced to go back to the drawing board and find a way to shrink down the design.
The solution they came up with was to remove two of the four Nixie tubes, and to implement a custom transformer. That transformer was provided by David Forbes of Cathode Corner, who sells watches very similar to this one. They also used a bare ESP32 on a custom PCB instead of using a pre-made module. Because there are only two Nixie tubes, this watch can only show two digits of the time at any given moment.
RemcoK3 first 3D-printed a prototype enclosure that has room for the 300mAh battery and other components, and then CNC-milled the final enclosure from billet aluminum. They also developed a custom smartphone app that lets them set the current time, along with a few other functions, through a Bluetooth connection. The finished watch is still a tad on the large side, but it’s amazing how much RemcoK3 was able to fit into such a compact case.