The Dekatron clock tells the time, without semiconductors

Over the years, several memory and display technologies served a particular niche for a time, only to be replaced and forgotten when more appropriate technology emerged. One of them was the dekatron: a memory and display tube combination that was used in the 1950s and 1960s but became obsolete soon after. Their retro design and combined memory/display functionality make them excellent components for today's clock hackers, as [grobinson6000] demonstrates in its Dekaclock project.

A dekatron tube is basically a neon tube with ten cathodes arranged in a circle. Only one of them is on at any time, and you can pop the tube to the next cathode by applying pulses to its pins. The Dekaclock uses the mains frequency of 50 Hz to generate 20 ms pulses in a tube; when it reaches 100ms, it triggers the next tube that counts the hundreds of ms, which triggers another that counts the seconds, and so on with the minutes and hours.

The Dekaclock uses no semiconductors: the entire system is built from glass tubes and passive components. However, [grobinson6000] also built an auxiliary system, full of semiconductors, which makes the clock a bit easier to use. It sits above the Dekaclock and automatically sets the correct time using a GPS receiver. It also keeps track of the time displayed by the dekatrons and tells you how far they have strayed from their initial setting.

Both systems are housed in sleek wooden cases that fit perfectly with the retro aesthetic of the tubes. [grobinson6000] was inspired to create the Dekaclock after looking at another dekatron clock we featured earlier, and designed the GPS receiver to work with it. Dekatrons are surprisingly versatile devices: you can use them to craft anything from internet speed meters to kitchen timers.