Yes, I have specific per-segment current limiting. The circuit is simple (NPN transistor with emitter resistor). I aslo have a current-limiter at the anode.
The problem with the 7971 datasheet numbers is that if you add-up all of the spec-value segment currents for an '8' character it's 40mA. In fact, most displayable characters will exceed to max anode current spec of 21mA. The rarity and high price of these tubes leaves no room for error. First, I created an excel spreadsheet that sums the current for each displayable character, using datasheet values Next, I scaled back the datasheet values so that in most cases, the total node current is within spec (21mA) Then I spent several hours plotting I-V data for all of my 7971 tubes (my new nixie bench supply REALLY helped with this task) For each tube, I visually determined a satisfactory on-current for each segment. The last step is to reconcile the individual segment current values with the visually-acceptable segment current, while factoring-in tube-to-tube variations. I'm still tweaking the segment currents; there still is an anode current limiter (21mA) to handle 3 outlying cases where anode current would exceed ratings without the limiter (*, Q, 8 characters). Admittedly, this design is probably overkill but I'm not taking any chances with those expensive tubes. Hera are the spec (top row), and scaled (bottom row) segment currents I'm using. As you can see, it just over half the datasheet value. In general, these currents produce decent illumination, at least with the tubes I have. 6 4 5.5 5 5.5 4 5.5 5 5.5 5 5 6 5 5 6 3.5 2.5 3.0 3.0 3.0 2.5 3.0 3.0 3.0 3.0 3.0 3.5 3.0 3.0 3.5 -- 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 neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/b0e36754-f7d2-4470-9198-1cc9f5c8692f%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
