No difference; current is current, and that is what determines how bright the glow will be. However, the circuits you posted are quite different. The anode-resistor provides current-limiting, but no current regulation: If the supply voltage or the tube's voltage drop change, so will the anode current. This can be undesirable, especially if it results in higher-than-spec anode current which can lead to premature failure.
The cathode circuit you showed will regulate the current, irrespective of the anode voltage or tube condition. You can also use a similar regulation technique at the anode; you would use a PNP or PMOS (my preference) device. I've used all of these techniques in my designs, and for the 7971 nixie clock I recently finished, I use *both* anode AND cathode current regulation. If you are using plentiful and inexpensive tubes, such as IN-1's, IN-8's, an anode resistor is fine. But if you are going for larger tubes like IN-18, 7971, or Dalibor's I would definitely use a current regulator. -- 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/116f57d7-4be5-49bb-81d6-6d75aa3fe47a%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
