<https://lh5.googleusercontent.com/-_PML27wwc9w/VO7hHsuYRwI/AAAAAAAAATA/LVcwCOp5mWw/s1600/IN17.jpg> I did mean to change R22 to 10k, but I can suggest an even better way. This is a circuit I've used to multiplex IN17s, with no dead period and no ghosting. It looks terrifyingly unsafe. Let me explain.
When the processor pin is high, Q1 base-emitter voltage is 0 and the transistor is cut off. The port pin sees no high voltage. When the port pin goes low the transistor turns on as a constant current source, the current set by (5 - 0.6)V/R2 or about 1mA. This drops 170V across Q1 and 10V across R1, which turns on Q2. Q1 is operating in linear mode, not saturated, so it switches in nanoseconds. Resistor R1 is necessary to help Q2 to switch off rapidly. This configuration of Q1 with the implied transistor inside the MPU is called a cascode <http://en.wikipedia.org/wiki/Cascode>. On Wednesday, February 25, 2015 at 3:45:43 AM UTC-8, joenixie wrote: > > Hmmm... interesting observation Pete, are you talking about changing R21 > or R22 to 10K? I chose 100K because I have them in my NixieNeon clock. > > -joe > > -- 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/9b60c133-a645-45b1-bb04-2e0eac84a923%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
