hilpert at cs.ubc.ca
Mon Mar 5 17:35:21 CST 2007
Jules Richardson wrote:
> Does anyone know if multiplexing Nixies will significantly reduce their
> lifespan? Or does it in fact help versus "permanently on as needed"?
> I'm not sure if it's rapid hot-cold switching that'll kill them or if it's
> simply down to "on time"... (or even neither :-)
> I'm reviving the Nixie-based Sudoku idea mentioned on here in the past as I
> think I've found a good source of tubes in the Ukraine. Latching every digit
> isn't an option (due to sheer number of ICs required), but likely failure
> causes dictates how many tubes will participate in each multiplex...
I don't have a definitive answer, but I think the issue is more peak current
than hot-cold switching.
Whether the life-determinant is absolute peak current or peak current
integrated over time though, I don't know.
Most test equipment is non-multiplex, while most calculators use multiplex
mode. In calculators the duty cycle is typically 1/12 to 1/16. The NIXIE's used
in test-equipment vs calculators are, by my observation, in pretty much mutually
exclusive sets: I've rarely if ever seen a NIXIE type that was used in one
equipment in one mode that was used in another piece of equipment in the other mode.
Consequently I have wondered whether there was a difference between NIXIEs
made for mux
mode vs. not (different gas pressure perhaps?), and have had my eye out for
manufacture data that might answer that, but haven't run across anything that
actually specified multiplex mode criteria.
Also, just by experience, I run into more bad NIXIEs in test equipment
(non-mux mode) than in calculators (mux mode).
Granted that it may well be other issues that are more significant in
producing those distinctions in observation (numeral size, operation
behaviour, period, etc.).
The anode limiting resistor gets dropped in value for mux
mode use (although not in linear proportion), with the consequent increase in
One or two Sudoku rows in a multiplex set might give some benefit of
multiplexing but still keep the duty cycle and peak current in 'typical' range.
I'm tempted to also build in an infra-red motion detector (adapt one of those
outside light sensors) to reduce un-utilised on-time in such situations.
I could supply you with some display-driver schematics from calculators, for
examples of how the anode drivers are typically done, if you like.
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