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 theold...@gmail.com 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:* neoni...@googlegroups.com <neoni...@googlegroups.com> *On >>> Behalf Of *Chris >>> *Sent:* Saturday, March 04, 2023 8:19 AM >>> *To:* neonixie-l <neoni...@googlegroups.com> >>> *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 theold...@gmail.com 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 neonixie-l+...@googlegroups.com. >>> 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 neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/dcac1e37-e222-463a-abbe-2820baa92290n%40googlegroups.com.
