Relay Logic Nixie Clock
Jon Stanley's Nixie clock output is controlled by timing signal and relay logic.
Modern digital computing devices, at their very core, are a series of transistor-based logic gates that turn on and off via input from other on-chip transistors. Today these gates are microscopic, making even a human hair seem gigantic in comparison, but at the end of the day they’re simply controlling the flow of electrons.
The same thing can be done with relays, at a much slower speed, and as a much larger device. Rather than study this as just a theoretical and/or historical concept, Jon Stanley has created a clock based on a timing pulse input and relay logic to advance the time display. Hours and minutes are displayed on a set of four Nixie tubes, while the seconds are shown advancing on a series of LEDs.
The results of this amazing clock can be seen in the first video below, laid out nicely on one PCB. The second video shows the same sort of setup with a series of relay PCBs and Nixie tubes chained together with connecting wire.
The project write-up gives a huge amount of background on how this circuitry works, building up the concept from relay CMOS gate equivalents, to logic schemes, and binary calculation techniques. There’s even a massive Nixie clock PCB, as well as relay logic modules for sale on Stanley’s Catahoula Technologies store, if you'd like to get started on your own relay/Nixie learning adventure.