Home Computers Projects Info

Nixie tube tester

DISCLAIMER: Things discussed in this article are potentially lethal, you make them at your own risk.

One of my first real projects that was taken to its completion. It is based around an SN7441. This is a special chip dedicated to nixie tube driving. Nixie tubes work in a counter-intuitive way. You apply 170v DC to a power pin and you then ground out the digits to make them glow. There are many simple boost converters out there to make this voltage. The majority of them are not current limited though. For safety in my design I put in a 20K resistor in series to the output of the converter; this is quite a large amount to some people but this also protects the tube and makes it run longer.

The 7441 accepts a BCD input, so you can simply use a BCD counter such as 7468 with a 555 timer and you then have a box which steps through the digits.

Nixie box

short video of it in operation

links an opinions

I do feel if you have to go through a lot of tubes building a box like this can be very worthwhile. There are a few snags though. SN7441s are a discontinued chip and as such are not cheap or simple to find. Nor are they very reliable, out of the set of 4 I bought 1 did not work.

A site of a similar project. However, I do not agree with their use of a microcontroller for such an application.