Mulitplexing and max. current through the nixies

3 years 3 weeks ago #7714 by mcc

please dont get me wrong here: THIS IS BY NO MEANS ANY KIND OF CRITISM !!!
I am just curious only....

* The 6 digit arduino nixie clock uses one driver chip (SN74141 or its russian colleaque) for all six digits.
Does this mean, that -- to acchieve the same brighness of the digits -- it uses a six time higher current
due to the multiplexing?

* The manual says, that a "faint crackling noise" can be heard from the hv generator while calibrating.
What is the source of that noise....?
(I would had guess a transformer...but there is no transformer....)


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3 years 3 weeks ago #7716 by Ian
Not taking it as criticism ;)

Yes, it does mean that. You'll find the anode resistors are quite low value (3k) and this is to allow a higher current to pass for that shorter time. The clock uses quite a few tricks to extend tube life, and it seems to work well: Linear dimming using the LDR, and a high frequency inner loop, (the multiplexing happens at ~ 100Hz), plus the blanking, ACP and so on. I have never had a tube fail in any of the clocks I have (and I have 3 IN-1 clocks at home, and they are more sensitive, because they are not mercury doped).

I've never managed to trace down the faint crackling sound, but it is to do with the modulation of the HV generation when the circuit is not loaded (i.e. when you are testing it the first time). It goes away when the circuit is loaded.

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3 years 3 weeks ago #7717 by mcc
Hi Ian,

thank you for your reply ! :)

I bought IN 12 B (hopefully the name of the type of the tubes is not converted to a smiley this time...) tubes.
I asked the seller what one can exspect of a lifetime in general from new old stock tubes, which were not
used a single time for about 40 years and he answered, that the datasheet says 7500 hours. But he had a
big "BUT": "BUT he has a nixie clock running since 2002 continously and not a single tube shows any
sign of age... "
This is exactly what you have noticed.

(Hopefully soon) I will have time to build my kit and then I will have a chance to experience "the mythical faint crackling". I will keep an eye/ear on it...we will see...curious what it may be...
How long are you running your clocks already ?

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