Nixie Clock Version 1

Posted on Feb 5, 2014

The clock was experimental until I picked up some experience with the circuitry. I experimented with the idea of building an alternating display using two B-5560 nixie tubes but ended up using 4 nixies instead. The original idea was to display the hours, then minutes, then the cycle starts again. The nixie tubes used in this clock are Burroughs B-5560 tubes that were salvaged from a small broken HP frequency counter.

Nixie Clock Version 1
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Those nixie tubes are mounted upside down and required a separate board to hold the nixie tubes and cathode transistors. The alternating display idea was to wire the collector ends of the 1 hour transistors to the 1 minute transistors and the 10 hour transistor (I did not use zero for the 10 hours at first) to a 10 minute transistor (only a digit 1 from the 10 hour). The emitter ends of the hour transistors were tied and separate from the tied emitter ends of the minute transistors. This meant I could feed in the signals to all the transistors as if all nixies were present, but one set of transistors` (hours or minutes) emitter ends would be grounded. Therefore, displaying only the hours or the minutes, if both sets of transistors were connected and grounded, the digits would overlap. I spent about a day wiring the board with the two nixies and the 27 transistors. I used a ribbon computer cable to carry the signals from the controller board to the switching transistors. It was very difficult to wire the ribbon cable to the two boards since most of the connections are thin and I was using a dull soldering iron. After the first board was completed and wired, I started on the controller board. I had problems with the hours not resetting correctly so I used another 4017 IC instead. I also used another 4017 IC for the 10 hour IC instead of the other 4013 half so I can display zero with my single digit hours (for example; 03:00,...

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