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, theoldpha...@gmail.com 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:* neoni...@googlegroups.com <neoni...@googlegroups.com> *On Behalf > Of *gregebert > *Sent:* Monday, March 06, 2023 8:13 AM > *To:* neonixie-l <neoni...@googlegroups.com> > *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 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+...@googlegroups.com. > > 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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