> Well, multiplexing is something different to the approach of direct > drive. There are far more ignitions within a tube, and I do not know > if that is good. I believe people talking about their muxed clocks > running fine for years or decades (!), but say you "overdrive" a tube > that is specified for 2mA with 2.5mA. Every time the tube fires, there > is too much current, and isn't that resulting in an increased > sputtering of the respective cathode? > > Jens
I'm not knocking direct drive. It just seems a lot of people knock multiplexing. All the nixie clocks I've made are multiplexed. I don't believe the constant ignitions hurt the tubes at all. I've watched the multiplexing process on a scope, and have found that nixies don't 'surge' upon ignition. In fact, there's a small delay (10 - 30us) where nothing happens after applying anode voltage. Then the current ramps up slowly (another 10 - 30uS, nominally), to the operating current, determined by the voltage drop across the anode resistor. As for overdriving it. I don't think a modest amount, say 2.5mA, if the max spec is 2mA (constant), will hurt it. I can't say anything about applying 8mA, for that same '2mA tube' is harmful (assuming 1 of 4 muxing; 25% duty cycle, hence 2mA average). There are people in this group, who have theories about such things, but I forget which way the general consensus went. I do know that 'under driving' is bad. If the minimum current is 1mA, and you only give it 750uA (0.75mA), then cathode poisoning may form over time. In the case, where the peak current exceeds the minimum, but not the average, it seems to sufficient to keep the cathodes clean. At least that's my experience from the clocks I've built. None show cathode poisoning. Only my 1st on has problems, but that's because I used IN-4 (non-mercury type) in the hours location, and the 10's hours zero, gets eaten away in about a year. I have lots of spares. Try using only mercury enhanced tubes. These are the 'long life' or 'extended life' tubes, at least for clocks, or other projects where the tubes are ON constantly. Mercury-free tubes are okay for intermittent apps, like volt meters, or a 'nixie watch' where they are ON for only a short time. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
