On re-reading your message, if one digit is lit, the voltage drop over the anode resistor can be calculated according to Ohm's law, and determines the "real" voltage present at the tube's anode (Ub - Ura). The remaining open switching transistors now see the calculated anode voltage minus the internal tube voltage drop. This is usually in the order of 70V or so, depending on your tubes and supply voltage. That voltage would jump significantly if all digits were switched off simultaneously, the condition I described in my first reply since there would now be 0V drop over the anode resistor. For that reason tube blanking should not be done by opening all cathode transistors unless they can handle that voltage.
Bill From: [email protected] [mailto:[email protected]] On Behalf Of Bill van Dijk Sent: Friday, October 23, 2015 8:14 AM To: [email protected] Subject: RE: [neonixie-l] How much voltage do cathode transistors need to be able to handle? According to Mr. Ohm, the voltage drop over a resistor is equal to the resistance multiplied by the current. In the off state, the current is 0A, so regardless of the value of the anode resistor, the drop over the anode resistor is 0V. The switching transistor therefore sees the full voltage minus the internal drop in the tube. Bill From: [email protected] [mailto:[email protected]] On Behalf Of alex nolan Sent: Friday, October 23, 2015 3:30 AM To: neonixie-l Subject: [neonixie-l] How much voltage do cathode transistors need to be able to handle? I'm struggling to get my head around this. But considering the following setup for a nixie tube, wouldn't the voltage across the cathode transistor be close to 0? Most of the voltage should be dropped across the tube itself, with the remained dropped across the current-limiting resistor, right? Does it have to do with the transistors keeping the other cathodes open? If so, how do we calculate those voltages given the tube is on, just to a different cathode? <http://www.mcamafia.de/nixie/images/nix_th01.jpg> -- 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 email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/d1f607aa-b969-4288-be51-c6bbf4f23fdf%40googlegroups.com <https://groups.google.com/d/msgid/neonixie-l/d1f607aa-b969-4288-be51-c6bbf4f23fdf%40googlegroups.com?utm_medium=email&utm_source=footer> . For more options, visit https://groups.google.com/d/optout. _____ <https://www.avast.com/antivirus> Avast logo This email has been checked for viruses by Avast antivirus software. www.avast.com <https://www.avast.com/antivirus> -- 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 email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/006001d10d8c%2451ed1710%24f5c74530%24%40com <https://groups.google.com/d/msgid/neonixie-l/006001d10d8c%2451ed1710%24f5c74530%24%40com?utm_medium=email&utm_source=footer> . For more options, visit https://groups.google.com/d/optout. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus -- 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/006801d10d8e%247a1db760%246e592620%24%40com. For more options, visit https://groups.google.com/d/optout.
