There are a few different datasheets at the bottom of this page: https://danyk.cz/avr_num_en.html and they all seem to mention the filament voltage starting at 3.15V - how much would this increase lifespan?
/Martin On Monday, 6 March 2023 at 17:19:31 UTC+1 Benoit Tourret wrote: > Thats the case on Mose's clock: one (bypassable) diode driving all the > "com" pins > > Le lundi 6 mars 2023 à 15:35:22 UTC+1, [email protected] a écrit : > >> Using a current limiter sounds like a LOT of circuitry, 7 times the >> number of tubes? I simply use a forward biased diode to drop the voltage, >> about 0.7 for a standard silicon diode, and about 0.3 for a Schottky. That >> requires only one or perhaps two diodes for the whole set of tubes. Perhaps >> not as accurate, but definitely a whole lot simpler. >> >> >> >> >> >> >> >> >> >> *From:* [email protected] <[email protected]> *On Behalf >> Of *gregebert >> *Sent:* Monday, March 06, 2023 8:13 AM >> *To:* neonixie-l <[email protected]> >> *Subject:* Re: [neonixie-l] Re: IV-9 numitron lifespan >> >> >> >> 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]. >> >> To view this discussion on the web, visit >> https://groups.google.com/d/msgid/neonixie-l/13ceb519-9b4d-469e-9e03-8d844e317239n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/neonixie-l/13ceb519-9b4d-469e-9e03-8d844e317239n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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