Update: success! I've found a way to limit current using few components and without any voltage dividers. The key was using a N-JFET. I guess if one used a N-MOSFET which opens with negative gate voltage, the result would be simmilar. I wonder if a similar circuit with a P-MOSFET would work, but I'm not going to check it soon. The schematic is ultra simple: https://i.stack.imgur.com/sKtpJ.png I used a BF256B (the only N-JFET I have laying around) and changed resistor to 1k. The current is limited to 2mA - I've tested it with voltages from 0 to 30V and as soon as I reach 2V across it, it starts blocking current. It changes slightly with voltage, on 3V across circuit it is exactly 2mA and with 30V it is 2,1mA, but I think it is close enough. A 270 resistor gives about 4,5mA, the difference between 5V and 30V is about 0,15mA - still very good, Drawbacks of this method? JFETs are only low voltage, max 30V difference between any two pins, usually. So to use those with Nixies, you'd have to use a resistor + this limiter - so if you have 50V to drop on current limiter and you want it to work on 2mA, you have to use a 22k resistor + this limiter to drop 44V across resistor and 6V on limiter. And, of course, it will blow if Nixie gets shorted, so whole circuit will have to drop 200V instead of 50v. I'll probably test this on nixies during next days.
Idea and schematics taken from http://electronics.stackexchange.com/questions/105326/is-there-any-physical-device-called-current-source/105394 -- 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/98e3cac4-6a49-4fbf-a15a-c15ca6ec3853%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
