> I'm looking at the english-translated datasheet for the IN-12A nixie, and am > a little confused by the specs. > > it mentions having a power supply voltage >= 200V, a discharge appearance > voltage <= 170V, and a discharge voltage of >120V. > > What is the difference between these specs? Which value should I design my > power supply for?
The "discharge appearance voltage" is the "striking" voltage - you need at least this much voltage to get the neon to ionize in the first place. The "discharge voltage" is the "sustaining voltage" - once the neon is ionized, the voltage across the nixie will be approximately this much. You need to accomplish two things to light a nixie - you have to start the discharge, and then you have to regulate the current though the discharge. The easiest way to do this is the way it's usually done: have a fixed voltage supply that's more than the striking voltage, and an anode resistor to limit the current once it's lit. The higher the supply voltage, the faster the nixie will light, and the better current regulation you'll get using a simple resistor. I suspect that's why they bother to specify a supply voltage. My nixie power supplies usually operate at 180 volts or so. To calculate the value of the resistor, subtract the sustaining voltage from the power supply voltage to get the voltage drop across the resistor and divide that by the desired current to get the resistance that will drop that voltage for the desired current. Keep in mind that the resistor used has to support both sufficient power dissipation and be capable of holding off the voltage safely. For example, assuming a 200 volt supply and an operating current of 2mA, you'd get an anode resistor voltage drop of 200 - 120 = 80 volts. Divide that by 0.002 amps to get 40000 ohms. To get the power dissipation, multiply the voltage drop (80 volts again) by the current (0.002 amps) to get 0.16 watts. An ordinary quarter-watt resistor would be sufficient, but I like to use half-watt resistors for high voltage circuits. That isn't the only way to do it, of course - that anode resistor approach is simple and effective, but it is not efficient - the resistor just converts the extra voltage to heat. It's possible to attack it differently by using a current-regulated anode supply instead - that's much more complex but efficient. - John -- 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 post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/8B2CAF19-19A8-40F6-8985-66AA19D73E0C%40mac.com?hl=en-GB. For more options, visit https://groups.google.com/groups/opt_out.
