[image: ScreenHunter_26 Apr. 29 11.35.jpg] I use a simple NMOS current-limiter in my HV supply. Basically, there is a resistor on the source lead, and the voltage-drop across that resistor provides negative feedback. To set the current-limit, I have a 10-turn potentiometer to set the gate voltage of the MOSFET.
In the posted schematic, the current-limiter on the left (Q1) uses a 100 ohm sensing resistor, and limits current from 0 to 100mA, up to 180V. The limiter on the right (Q2) is for 0 to 20mA, up to 500V and uses a 1K sense resistor. Both transistors need hefty heat sinks in worst-case operating conditions (voltage set to max, current set to max, outputs shorted). I wouldn't risk my life with this circuit, but I did test it on my finger at 500V, around 150uA, and barely felt the current. It's perfectly safe for nixies, and I've used it to evaluate all of my valuable tubes (b7971 and R|Z568M) with no damage. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/d9bc36a6-0c83-401c-81b1-f748eac5a0d8%40googlegroups.com.
