Nixie model for LTSpice?

[Dekatron42]

Hi,

Does anyone have a working model for a Nixie for LTSpice - I've tried to make one with the Neon-tube available in the library but I can't get it to work as I want.

/Martin

[gregebert]

I use a diode in-series with a power supply (about +160V). If you are a purist, you can add some series resistance.

It's not an accurate model but it will get you in the ballpark for most designs. It will NOT suffice if you need to model ionization, because that happens at a higher voltage than while glowing.

If your design requires a very accurate model of a nixie tube, then I would re-examine the circuit because it's too sensitive to varying nixie-tube characteristics.

I've plotted  IV curves for all of my b7971 tubes (because of their high value) and found that over the proper operating region they are fairly linear; the slope representing the resistance of the tube at that point. As far as ionization voltage is concerned, it's not easy to measure accurately and it varies a lot from tube-to tube. I always use anode supplies above 200V to allow adequate margin for ionization.

There are models online for NE-2 bulbs which include the effects of higher ionization voltage and it's overall non-linear behavior, so you could modify it accordingly for a nixie tube.