You are absolutely right. 5v was not high enough despite Ronald's and my confirmation that it would work. I am changing to +25v and -25v and will have an optocoupler with the diode driven from the 5v PIC and the transistor at the bottom of the resistor between the two power supplies. It keeps it simple. I have to order the optocoupler because none of my old ones have higher than 30 v rating. I will have to think about the extra two power supplies. Maybe I can't avoid them. It will be a few days until I get the parts. Peter [image: Dekatron Circuit.jpg]
On Sun, Feb 14, 2021 at 3:18 PM Jon <dekat...@nomotron.com> wrote: > Interesting approach - not seen it rigged up quite like that. Let us know > how it goes! > > My immediate question is whether there's a big enough potential difference > between an inactive guide and a main cathode to get a reliable transfer > forward from a deactivating G2 to the 'next' main cathode rather than back > to the adjacent recently used G1 - 5V is much lower than the datasheet > guide bias. Might be OK at slow stepping speeds with long guide pulses. > Also the leading edge of your guide pulses is going to be fairly slow as > Q1/2 come out of saturation and the guides are passively pulled down to the > 'active' voltage. Most guide drive circuits use a NPN pull-down to the > active state which creates a sharp leading edge and then a slower return to > the inactive state. > > Jon. > > On Sunday, February 14, 2021 at 7:06:28 PM UTC bung...@gmail.com wrote: > >> Having finished the Amperex 8453 display I started on my Dekatron. Thanks >> to all for the suggestions. >> I read up on Ronald Dekker's clock project >> https://www.dos4ever.com/decatron/decatronweb.html >> and decided against a direct drive from a 74141 because, even if it was >> practical, it would not look as good as using all the pins. It would look >> like the 8453 I just finished except without the number mask. >> A few quick experiments showed that a -24v power supply was needed for >> the easiest implementation.. This is my design. I will let you know if it >> works. >> >> A PIC drives the circuit: it starts with Q3 off to force a start at 1. A >> high on R3 or R4 is the same as the switches in Ron's test circuit placing >> -24v on the guides. As my PIC sends the BCD for the other displays and >> clocks the E1T it will generate the sequence to advance or retard this >> Dekatron.. >> [image: Dekatron Circuit.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+unsubscr...@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/62979e37-ef21-46e1-9b7c-45a4c4080238n%40googlegroups.com > <https://groups.google.com/d/msgid/neonixie-l/62979e37-ef21-46e1-9b7c-45a4c4080238n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- 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 view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/CAFxqQoJG8wcObT98OT-cyaMt2fMJFT2UQ%2B%3DGCNChTi9iCPcpCA%40mail.gmail.com.
