>> Thanks... But again, what kind of voltage should I set the supply to? >> Many seemed to think that 170v was enough, but I guess not...
I'd go at least 180V, maybe even higher (190V-200V). For a couple of reasons. One, your muxing it. Nixies don't turn-ON instantaneously. There is some turn-ON delay, which is a function of supply voltage. The higher the voltage, the quicker the neon ionizes. If you choose 170V or less, it might be just fine for a direct drive design. On a mux'd design you may experience some erratic behavior, and come back to us wondering why the tubes are flickering, even if you picked a total refresh frequency over 100Hz. Also, if you want to implement PWM dimming to do some fancy effects like cross fading, you want consistency, which a quick turn-ON time will give you. Turn-ON times, at 190V, is in the 20-40uS territory for standard size nixies. There's no period literature on this. I found out by running a few experiments, and reporting it back to this group. Reason two, the higher the supply voltage, the lesser will be the variation of anode current, with variation of the tubes inherent maintaining voltage. The maintaining voltage is usually between 130 to 150V. Say your using a 170V supply, and you design more the middle, 140V. Pick 2mA. 170V-140V=30V dropped across the anode resistor. 30V/2mA=15K resistor. If the one tube sets in at 130V, then it will draw (170V-130V)/15K = 2.7mA. Another tube set in at 150V, and it will draw (170V-150V)/15K = 1.3mA. That's a two to one variation. If you up the supply to 190V, and pick the same (hopeful) target spot of 140V, and 2mA. The anode resistor is (190V-140V)/2mA= 25K. Pick a 24K part. Again if a tube comes in at 130V, then the real current is (190V-130V)/24K = 2.5mA, and the other tube at 150V is (190V-150V)/24K = 1.7mA. The variation is reduced to ~50%. For 200V supply with all else being equal, the results are a 30K resistor, and anode current variation from 1.7mA to 2.3mA; 35%. In all cases, however, you are still in the operating specs of most standard size (0.5"-0.6") tubes. That's why you can continue with your design and not wait til your tubes come in. Note big IN-18s should run at 4mA minimum. OT: The 'supply trick' also works with LED displays. And you'll get much better consistency going with a 12V supply over a 5V supply. I 1st did this in the early 80s with a mux'd 8 digit 7-seg display. Not only did I have to consider the variation of the forward drop of LEDs (equivalent to nixie's maintaining voltage), but also the variation in saturation voltage of both the anode and cathode drivers. At 5V, all those 0.2V & 0.5V (and God forbid, 0.7V) drops add up. At nixie voltages, a half a volt, or even a volt or two, here and there, are no cause for alarm. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
