The picture above confirms my suspicion that more-frequently-changing digits will die first. The dying hours tube is still a mystery to me; maybe it was previously used ? I learned about this as a kid when I would do stupid things like turning my room light on-and-off to annoy others. Yeah, my bulb always died pretty quickly...
There are 2 design enhancements you can do to prolong filament life. First, limit the inrush current by using a simple current regulator or drive from a higher voltage and add some series resistance. For example, if a filament typically runs at 40mA for a 5V supply, it's HOT resistance is 5/0.04 = 125 ohms. I've seen cold resistance 4-5 times lower, so such a bulb could easily see surge-currents of 200mA. Now, if you drive the same filament from a 12V supply, and add a series resistance of (12-5)/0.04= 175 ohms, the peak surge current has been reduced to 60mA. This will reduce thermal shock, but not thermal cycling. For rapidly-changing digits, such as the seconds, you may want to have all segments slightly energized just below visibility to reduce thermal cycling. I would guess somewhere around 10-20% of normal operating current is a good place to start. What about PWM ? Well, that's a good question and I suppose if the frequency is high enough, say hundreds of Hz, there wouldn't be any added thermal cycling. But you would likely hear some audible noise. Faster still, say 20-30 kHz, wont be audible but might have some unwanted harmonics that cause RFI in the AM band. On Saturday, March 4, 2023 at 10:52:05 AM UTC-3 theoldpha...@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/67a3dca1-ba1c-4d46-aea5-fcb3c913e9ean%40googlegroups.com.
