Just to elaborate a bit more, the individual segment currents of a b7971 are different, due to different lengths. Since these tubes are getting quite rare, not to mention expensive, I also recommend anode-current limiting in addition to the individual cathode drivers. Per the datasheet, the maximum current for a b7971 21mA and individual segment currents range from 4 to 6mA. So the '8' character would draw 32mA (violating datasheet spec of 21mA) if you simply drive the segments at their rated current. In my case, I slightly decreased the segment currents below datasheet limits based on visual testing.
I have 8 tubes running in my 7971 clock; for my HV supply I rectified+filtered the AC-line voltage (about +170VDC), and boosted it by another 24V with a small DC supply. That's around 170mA of current in the worst case. I admit this is a dangerous thing to do if you dont know what your're doing with regard to safety, etc. But in my opinion, anyone talented enough to build their own nixie clock will follow good circuit-design practices with adequate fuses, surge protection, shielding, and ventilation. None of the six 'hot chassis' clocks I've built so far has had any component failure, other than a nixie tube (and even that is rare, with 2 tubes out of 47 getting dark coating inside the glass). -- 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/06152ff5-0065-402a-8845-f9e5229e93ab%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
