Nixie Questions and Answers

high-voltage supply:

Q: Is it possible to derive the high-voltage supply for nixies directly from the mains?
A: Yes! But be careful, touching any conducting part of your circuit can be lethal. If you are not familiar with working with mains fed circuits first read this. Examples of clocks which are fed directly from the mains are the Tube-in-Tube clock, my single-tube E1T clock, and Geert’s single digit nixie clock.

Q: When I use the mains for the HV supply, do I still need a transformer for the low voltage supply?
A: Not Necessarily. When the low voltage circuit draws only a few mA, it is sometimes possible to use a dropper capacitor. But be careful, touching any conducting part of your circuit can be lethal. If you are not familiar with working with mains fed circuits first read this.

Q: How can I dim my nixie tubes when the mains is used for the HV supply?
A: Exactly the same way as you would dim the lights: with phase-cutting.

Q: How does a switched-mode DC-DC converter work, and how can I make one for the high voltage supply of my nixie tubes?
A: An extensive explanation of boost- and flyback converters can be found on my ”Flyback Converters for Dummies Page”. It contains a description of a simple HV boost converter, a simple flyback converter, and an inductor test-bench.


Q: What is the best choice for the time-base of my clock, the mains frequency or a crystal-oscillator?
A: In most countries – at least here in Europe – the long term mains frequency is extremely well regulated. A crystal oscillator requires accurate trimming and is susceptible to ambient temperature variations. Therfore, provided that the mains is well filtered from transients, I therefore prefer the mains frequency.

driving nixies:

Q: What happens when a transistor breaks-down, and what is the difference between BVceo and BVcbo?
A: Read my Junction Break-down for dummies section.

Q: Is it possible to use low-voltage transistors to drive a nixie tube?
A: Yes and No. Usually only the BVceo of a transistor is specified. This is the breakdown of a transistor with open base. The BVcbo, breakdown with base connected, is usually much higher. Have a look at the Tube-in-Tube clock for a design example.

Q: When a transistor goes into avalanche breakdown will it be damaged?
A: No, an avalanche breakdown will only damage the transistor when the maximum dissipation of the transistor will be exceeded.

Q: Is it possible to construct a ring counter with a nixie tube?
A: Yes and No. Unfortunately the difference between the striking and maintaining voltage of most nixie tubes is too small to use that for construction a ring counter. However, it is possible to construct a nixie ring counter using a Shockley diode or the snap-back of a single transistor.

Q: What is the simplest way to make a nixie counter/driver?
A: To my opinion the nixie ring counter with snap-back transistors is one of the simplest, cheapest, and most elegant nixie counter circuits.

Q: Is it possible to drive a nixie tube directly by a HEF or CD4xxx CMOS gate?
A: Certainly, provided that the gates are operated from a 15V power supply.

Q: How do I drive a Bi-Quinary nixie tube like the ZM1030 or ZM1032?
A: Bi-Quinary nixie tubes have two groups of five cathodes, each with their own anode. To use these tubes you need two separate “high-side” anode drivers.

Questions and Answers related to other display devices

Q: What is a neon ring counter and how does it work?
A: A neon ring counter is a circuit that uses only neon tubes, diodes, and capacitors to count pulses. Visit my Ring Counters for Dummies section for a detailed explanation.

to top of page back to homepage