Recently I salvaged a piezo humidifier driver board which produces high frequncy AC volage. Naturally I decided to touch it's output. It hurt so I deduced there might be enough voltage to power a nixie tube with it. To my surprise it lit up, but with purple flares around cathodes. So the questions are: what are the drawbacks of powering a nixie tube with high frequency AC, why does it even work and what are these flares?
The issue is current, not frequency. Nixie tubes require a series impedance to limit current to jut a few milliamperes or they will be destroyed. Glow discharge tubes are damaged by sputtering (atoms knocked out of metal by ions), also called "poisoning". Doubling the current cuts useful lifespan by roughly a factor of 10!
Humidifier piezoelectric drivers operate at a few watts power, and without a series resistor (or, for AC, capacitor or inductor), the device won't last very long.
That said, there are other issues with using the humidifier power supply:
- As others have mentioned, how would you control which elements (digits) are lit? For AC control, you might use an 11-position rotary switch (0-9 and off), but most semiconductor circuits need DC.
- N.B. The PCB shown does not appear to be isolated from the AC mains, and would pose a severe electric shock hazard.