Very interesting. Others who have multiplexed nixie tubes, which run at a lower current, have reported audible noise. I would expect more noise at higher currents due to magnetism effects, but that isn't happening here with your numitrons. I've heard it myself with incandescent bulbs; I havn't done any work with numitorns.
On Tuesday, March 7, 2023 at 6:00:25 PM UTC-3 Moses wrote: > Gregebert, > > I've not heard these tubes at all. I was initially running them at 100Hz, > then changed to 400Hz for a while before settling at 1600Hz. > I've got half a dozen prototypes running for several months, so if they > were going to make noise I would have heard them by now. > > Neat idea on measuring the time-constant, I'll give it a try. > > Regards, > -Moses > > On Monday, March 6, 2023 at 5:12:55 AM UTC-8 gregebert wrote: > >> Very good info, Moses. >> >> From that, I would target the operating current well-below 20mA to >> prolong the life of the display. You could use an NPN current-limiter >> (driver) driven from 5V TTL logic. Let me know if you need circuit details, >> but it's a very simple design (1 NPN + 1 emitter resistor). As a starting >> point, a 270 ohm emitter resistor will limit current to 16mA. >> >> Do you hear any noise with your PWM running at 1600Hz ? If not, I would >> stick with PWM and not use the NPN driver, as it's not necessary. As long >> as the PWM cycle-time is shorter than the thermal time-constant of the >> filament (probably a few milliseconds), you should be fine. I think you can >> measure the thermal time-constant of the filament with a phototransistor >> and a scope. Starting at a low PWM frequency, the phototransistor will show >> fluctuations in the bulb's intensity. As the frequency is increased, you >> should see the amplitude decrease towards zero. I've never actually done >> this but I'm pretty sure it will work. You have to use a phototransistor >> (or photodiode); a CdS photosensor will have too-slow of a response time. >> >> On Monday, March 6, 2023 at 2:37:45 AM UTC-3 Moses wrote: >> >>> The TI CD4511B datasheet lists the lists the *minimum* high level output >>> (at 5v VDD) of 4.1v but typical is 4.55v, maybe others are different? >>> >>> https://www.ti.com/lit/ds/symlink/cd4511b.pdf >>> >>> At 4.55v the segment current on the IV-9 is going to be about 25ma. >>> Typical IV-9 segment current is about 20ma I believe, so that would be a >>> 25% overdrive. >>> >>> I've put up a drive voltage vs segment current table on my site, maybe >>> it's useful to someone: http://www.neonixie.com/IV-9-6D-RR/#tech >>> >>> I settled with powering the tubes in my designs in one of two ways.. >>> 5.0v direct with a recommended PWM of about 65% (the 165 (out of 255) value >>> in the table) OR 5v through a regular silicon diode, dropping the voltage >>> to about 4.2v at the tube and PWM that to 76%. Both result in a segment >>> current of 20ma. Don't know if one or the other is better in regards to >>> lifetime, I was not able to find any official sources of information. I >>> experimented with driving them using a 3.3v regulator.. but at that voltage >>> they were a bit dim. >>> >>> NOTE: The IV-9 datasheet does mention to avoid running the tubes at a >>> frequency between 105 and 1000 Hz, presumably to avoid mechanical >>> resonance. I elected to run them at 1600 Hz. >>> >>> I looked through some of my testing data.. at a segment current of 3mA >>> the segments are visible, 2mA they are "barely visible" and at 1mA I noted >>> them as not visible. Keeping the unlit segments warm with a slight current >>> seems to make the most sense to me. It's all software on my clock so maybe >>> an option for the next revision. >>> >>> That's all I know so far. >>> >>> Regards, >>> -Moses >>> On Saturday, March 4, 2023 at 5:52:05 AM UTC-8 [email protected] >>> wrote: >>> >>>> Hi Chris, >>>> >>>> >>>> >>>> The numitrons are driven by a 4511 decoder, and according to their data >>>> sheets the max. output at that voltage is 4.1 V, so that is well within >>>> specification for the tube. Yes, I agree, lowering the voltage even >>>> further >>>> should increase lifespan. >>>> >>>> >>>> >>>> Bill v >>>> >>>> >>>> >>>> *From:* [email protected] <[email protected]> *On >>>> Behalf Of *Chris >>>> *Sent:* Saturday, March 04, 2023 8:19 AM >>>> *To:* neonixie-l <[email protected]> >>>> *Subject:* [neonixie-l] Re: IV-9 numitron lifespan >>>> >>>> >>>> >>>> Hi, >>>> >>>> While i am not sure for the IV9 numitrons have a look at the DA2300 >>>> lifetime expectancy, >>>> >>>> >>>> >>>> Basically reducing the voltage increases the life expectancy >>>> exponentially. >>>> >>>> So i usually run my numitrons at 4.5V or lower and have had no issues >>>> so far. >>>> >>>> On Friday, March 3, 2023 at 8:05:48 PM UTC+1 [email protected] wrote: >>>> >>>> I seem to recall there was some discussion on the life expectancy of >>>> IV-9 numitrons some time ago. >>>> >>>> >>>> >>>> In 2015 I built a number of clocks with these tubes, and they started >>>> failing last year. The clock in the picture is on my bench now, the three >>>> good tubes were replaced in November last year. So today all 6 tubes will >>>> be replaced. I have replaced all 6 tubes on a few other clocks also. One >>>> or >>>> more segments will no longer light up, and I do not see any blackening of >>>> the glass tube (The black you see in the picture is my permanent marker, s >>>> I will not replace the wrong tube when I disconnect the power). >>>> >>>> >>>> >>>> The tubes are driven directly from a 4511 chip on a 5V power line. >>>> >>>> >>>> >>>> There does not seem to be any order in which they fail, so I do not >>>> have the feeling that any of the tubes are significantly impacted by >>>> thermal stresses from flashing on and off. I would say based on my >>>> experience with them, the expected lifespan is about 7 years of continues >>>> use. >>>> >>>> >>>> >>>> Bill v >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "neonixie-l" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To view this discussion on the web, visit >>>> https://groups.google.com/d/msgid/neonixie-l/81b5b7e6-d476-4b83-9a8e-c9d6cc468db9n%40googlegroups.com >>>> >>>> <https://groups.google.com/d/msgid/neonixie-l/81b5b7e6-d476-4b83-9a8e-c9d6cc468db9n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. 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