Skip to content

Safety

This project uses dangerous voltages

The dekatron runs from about 450 V DC and the Nixies from about 170-180 V DC. A shock at these voltages can cause serious injury or death, and capacitors can hold a charge after the power is off. If you build, test or copy anything from this project, you do so entirely at your own risk. Work on it only if you understand high-voltage circuits and know what you are doing. Everything here is provided as is, without warranty of any kind.

This site explains how the tubes work; it is not a substitute for experience with high voltage. The circuits shown are real and were really powered, by someone who knew the risks and took precautions.

The bench test

The bench circuit on the dekatron page is the most exposed part of the project: open wiring on a perf board, the anode at up to 450 V and every other wire at 50-106 V, none of them at ground. If you try anything like it:

  • One hand. While anything is powered, keep one hand away from the circuit, for example in a pocket. Press buttons by their insulated caps.
  • Limit the current. Use a bench supply with an adjustable current limit, set to a few milliamps (2-3 mA for this test).
  • Power off to touch. Make and change connections only with the supply off and its output discharged; measure before you touch anything.
  • Rated equipment. Use meters, probes and leads rated for the voltage. Clip leads on before powering up rather than holding probes on live nodes.
  • Not alone, not tired. Work with someone nearby, and stop when you are not concentrating.

The finished display

On the boards, discharge paths, clearances and probe ratings are design requirements, not afterthoughts. Printed plastic parts keep fingers away; they are not high-voltage insulation. The detailed precautions for each step are in the bring-up procedures.