IN-12 dead time

[Leonardo Lisa]

Hello,

I'm working on a IN-12 based nixie clock, the clock is based on k155id1 cathode driver and the 4 digits are multiplexed. I'm would like to know if some one has done some long term term test about multiplexing frequency and dead time between the turn on of each digit. Any suggestion or good practis?

[David Forbes]

I built a bunch of multiplexed clocks in 2001-4 using the 74141 chip, which the Russian chip is a copy of. I used various Burroughs and Philips tubes.

I found that the multiplexing worked well on a PC board, with 100 microseconds to a millisecond of dead time before changing the binary value at the 74141 inputs. This time is needed to allow the tube to stop ionizing, so that the next number's ghost won't appear on that tube. 

On Fri, Oct 23, 2020, 5:56 AM Leonardo Lisa <leonar...@gmail.com> wrote:

Hello,

I'm working on a IN-12 based nixie clock, the clock is based on k155id1 cathode driver and the 4 digits are multiplexed. I'm would like to know if some one has done some long term term test about multiplexing frequency and dead time between the turn on of each digit. Any suggestion or good practis?

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[Dalibor]

From what we measured, the afterglow disappears almost completely after 200uS, this should be enough for the dead time. The afterglow and ionization are two different processes - the tube stays ionized (presence of electrically charged particles) around 1mS while the afterglow (presence of particles in an excited state). It is a good idea to keep the dead time higher than 200uS to make sure the afterglow disappears, but not longer than 1mS - after this time there might not be enough ionized particles to strike the next digit instantly.

We made a video about it, you can see how the afterglow looks at 200 000 FPS: https://youtu.be/TK3E55fytC0?t=1376

There is also visible how fast the new digit strikes when there is no dead time left to deionize the gas - it is instant, well below 5uS resolution of the camera.

Cheers

[Leonardo Lisa]

Hello guys, Please accept my apologies I was really busy and only right this week I was able to resume my nixie project. I working really hard in order to make bug free the firmware and to complete the project by the end of the month. I tried to follow your advices and these are the results: the display works great and these are the anode and cathode waveform. Any suggestion?