I'm pulsing them slowly for the visual effect and letting them overflow because I think they look very attractive while they count. The rightmost tube cycles every second but that's too frequent for the rest of them and the visual display just looks messy that way, so I opted to cycle them every 10 sec. Each cycle begins with a reset pulse so I'm sure the tube is at zero and then is deliberately overflowed 2 or 3 times to extend the display time of the counting. There are literally an infinite number of ways that could have been done and I may yet try changing them for different visual effects.
The tubes do have a "carry" output which was also used in their original application to reset the count but I chose not to use it to reduce complexity, so the micro needs to keep track of how many pulses have been sent to each tube and reset it on every tenth pulse. I originally toyed with the idea of running the tubes as per the data sheet with a twin triode reset multivibrator but decided it wouldn't look so good and would just generate more heat. I could have used transistors but it was easier to just to it in the micro. And there was also an issue of having enough CPU I/O pins available without coding or multiplexing. In this clock each tube requires two lines, for a total of 12, and if I wanted to read the carry that would make it 18 and and would require six level shifting interface circuits with one or two transistors as well. The chip has 32 I/O pins but many are needed for other things. In the final version there's only one spare! Yes, the nixie is running at its rated current or just below. I like the idea of pulse modulating it to reduce its brightness. It's fed through a 74141 so just sending it a number between 10 and 15 will blank it. VFD? In retrospect I could have done that but I do like the look of the nixie glow against the red wood. There's still a little more firmware tweaking to be done, but it's great to see it going now after months of (very part time) work! Cheers Morris On Feb 5, 5:42 am, threeneurons <threeneur...@yahoo.com> wrote: > > Yes, but to go from 1 to 2, this clock appears to go > > 1-2-3-4-5-6-7-8-9-0-1-2. It's > > eye catching, but I'm unsure as to why. > > > - John > > I hadn't noticed that. I'll have to view the video again. Morris will > probably tell us what's going on. > > It is uC driven, and can count upto 30KHz. Its quite possible, that > Morris is pulsing quickly (faster than we can see) from 0 to 1 to 2. > Then more slowly from 2 thru 9. Reset to 0, followed by a slow 1 and > 2. The cycle then repeats. > > The count following, 9 will be the 11th "carry" position, were the > carry signal is generated. In older circuits for this tube, that carry > usually also generates a reset pulse. To get better control, that > signal could be routed to a uC input, and a separate uC output goes to > the tube's reset input. Level shifting circuitry implied. Of course, > only Morris knows for sure. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
