Thanks Bill! Is there any way to calculate that internal voltage drop when for unpowered cathodes (or when all the cathodes are off)? I don't believe I've seen it on any data sheet.
On Friday, October 23, 2015 at 8:29:41 AM UTC-4, Bill v wrote: > > 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:* neoni...@googlegroups.com <javascript:> [mailto: > neoni...@googlegroups.com <javascript:>] *On Behalf Of *Bill van Dijk > *Sent:* Friday, October 23, 2015 8:14 AM > *To:* neoni...@googlegroups.com <javascript:> > *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:* neoni...@googlegroups.com <javascript:> [ > mailto:n...@googlegroups.com <javascript:>] *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 neonixie-l+...@googlegroups.com <javascript:>. > To post to this group, send email to neoni...@googlegroups.com > <javascript:>. > 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. > > > ------------------------------ > > [image: Avast logo] <https://www.avast.com/antivirus> > > 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 neonixie-l+...@googlegroups.com <javascript:>. > To post to this group, send email to neoni...@googlegroups.com > <javascript:>. > 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. > > > ------------------------------ > [image: Avast logo] <https://www.avast.com/antivirus> > > 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 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/8f746afa-cf38-46e6-b7af-53de985d2250%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
