Date
1 - 18 of 18
Nixie lifetime and multiplexing
David Forbes <dforbes@...>
Folks,
Here is a repeat of a message I sent to this list early on in its life... ------------------------- I've been looking for the answer to the Nixie lifetime qustion - is multiplexing going to shorten or lengthen tube life? I finally found an answer, by reading about neon lamp lifetime. According to several sources, the standard neon lamp has a lifetime proportional to 1/I^3.3 where I is the operating current. This means that if you run the lamp at twice the recommended current, then the lifetime will be reduced by a factor of ten. For a multiplexed clock display, if you run a 6-digit display at 1.7 times the recommended current, then the display will last just as long as a non-multiplexed display running at the recommended current. I have found that a current of 1.6 times the recommended value (using ZM1010 or ZM1020 or ZM1040 tubes) puts out enough light for a multiplexed 6-digit display used indoors. So there you have it. The tubes in a multiplexed clock should last the same number of years as those in a non-multiplexed clock. --David Forbes, Tucson, AZ http://www.cathodecorner.com/
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Raymond Weisling <fire.mountain@...>
##### level-1 quote by David Forbes (on) 01.04.02 (at) 09:19 -0700
Folks,That's the one, David, thanks for re-posting it. (Sometimes classic posts are worth re-posting rather than sending multiple people on a lengthy search of the archives, especially when it is topical.) --ray
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"ajfranzman" <a.j.franzman@...>
--- In NEONIXIE-L@y..., Raymond Weisling <fire.mountain@p...> wrote:
##### level-1 quote by David Forbes (on) 01.04.02 (at) 09:19 -0700It might not be so bad if doing an archive search would paginateSo there you have it. The tubes in a multiplexed clock shouldThat's the one, David, thanks for re-posting it. (Sometimes classic based on number of results returned from the entire archive, rather than arbitrarily breaking it up into (400+ message) chunks beginning with the most recent message. If you do a search for something which only appeared in an early message, you have to click through page after page CONTAINING NO RESULTS until you finally find the message you wanted. Do you think there's a snowball's chance that Yahoo might do something about this if we petition them? A.J.
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"ptsearcher2001" <ptsearcher2001@...>
--- In NEONIXIE-L@y..., David Forbes <dforbes@a...> wrote:
Folks,1.7 times the recommended current, then the display will last just as long asa non-multiplexed display running at the recommended current.the same number of years as those in a non-multiplexed clock.But, to my Experiences with Muxed LEDs, the Current has to be much higher: if you multiplex 6 Digits, the current is on for max. 1/6th of the total time, so has to be 6 times normal current. (Same applies for 4-digit: replace every 6 with 4) The effective Current is then the same! I asked a few 'Experts' about this, but none has Experience with tubes. Does this rule of thumb not apply to them????
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David Forbes <dforbes@...>
At 2:50 AM -0700 4/2/02, ptsearcher2001 wrote:
--- In NEONIXIE-L@y..., David Forbes <dforbes@a...> wrote:Odd. My experience shows that you don't need anywhere near 6 times theFolks,1.7 times current to achieve a usable display; on the contrary, 6 times the current would cause the tubes to act funny. There is a brain phenomenon called persistence of vision that comes into play here, which makes the bightness-vs-duty-cycle curve nonlinear. I don't believe that LEDs need anywhere near N times the current either. For example, a typical 8-digit LED calculator certainly does NOT require 100 milliamps per segment - if it did, then the batteries would last only 15 minutes! I believe that they typically use about 2-3 times the non-multiplexed current in calculators. The best way to find out for yourself how much current is really needed is to take a Nixie tube and run it at a fractional duty cycle, then vary the current with a variable resistor and look at the tube. You may be surprised at what you find. --David Forbes, Tucson, AZ http://www.cathodecorner.com/
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Raymond Weisling <fire.mountain@...>
Odd. My experience shows that you don't need anywhere near 6 times theThis is good -- it begs a side-by-side A-B test, both of nixies and LEDs. One of the devices is run at a DC current and the other is subject to a variable duty cycle and variable current. Adjust them for identical apparent intensities, and do so at different current levels for the DC drive one as the "standard". Who wants to do it? It should be done both in a dark room and in a bright room, as the eye will likely exhibit different time-decay persistence phenomenon depending on the amount of visual purple and whether the receptors are predominantly rods or cones. Ray
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"ptsearcher2001" <ptsearcher2001@...>
--- In NEONIXIE-L@y..., David Forbes <dforbes@a...> wrote:
Odd. My experience shows that you don't need anywhere near 6 timesthe current to achieve a usable display; on the contrary, 6 times thecurrent would cause the tubes to act funny.into play here, which makes the bightness-vs-duty-cycle curve nonlinear.either. For example, a typical 8-digit LED calculator certainly does NOTrequire 100 milliamps per segment - if it did, then the batteries wouldlast only 15 minutes! I believe that they typically use about 2-3 times theneeded is to take a Nixie tube and run it at a fractional duty cycle, thenvary the current with a variable resistor and look at the tube. You may besurprised at what you find.Yes and no! I meant the impulse current is a few times higher! for example: in IR Remotes the LED is driven with impulse current up to 1.5 Amps, while Datasheet says Imax 100ma const. Pulses are below 1 percent, so effective current is only 15 milliamps, way below imax! My idea was to keep the active current below the Imax (10ma for my tubes), with 1/6 duty cycle (hh:mm:ss), leads to effective 1.6ma, which is below the recommended maintaining current of 2-2.5ma. the overall current is full-time 10ma, as it would be with 6 steady-on- tubes at 1.6ma. Where is my fault of thought???
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"fixitsan2002" <fixitsan@...>
--- In NEONIXIE-L@y..., Raymond Weisling <fire.mountain@p...> wrote:
theOdd. My experience shows that you don't need anywhere near 6 times currentcurrent to achieve a usable display; on the contrary, 6 times the comes intowould cause the tubes to act funny. either.play here, which makes the bightness-vs-duty-cycle curve nonlinear. requireFor example, a typical 8-digit LED calculator certainly does NOT last only100 milliamps per segment - if it did, then the batteries would needed is15 minutes! I believe that they typically use about 2-3 times the vary theto take a Nixie tube and run it at a fractional duty cycle, then surprisedcurrent with a variable resistor and look at the tube. You may be Not me. (assuming we are looking for which method provides maximumat what you find.This is good -- it begs a side-by-side A-B test, both of nixies and lifetime) I'm kindof 'busy' for the next 10 years. Forgive my inaccurate quoting but was it 'if you double the current you decrease the life by a factor of ten' ? Makes Davids mention of 1.7 make sense now. Your tube is only on for 1/6th of its life whereas the direct drive is always on.(assuming you never turn of the display) Who, in the direct drive camp, run at maximum current anyway ? Isnt it the nature to put a few more Kohms on the anode resistor to make the tubes last longer at the expense of running a bit darker. What standard are we talking about when we assume a multiplexed display is dimmer, dont we mean 'cant ever be as bright as the brightest of direct drive displays'. As David mentioned, you dont need six times the current either, and isnt it interesting how a tube in a multiplexed display has a *lot* more brightness than a mathematical 1/6th of the brightness of a direct drive display. Hey, it is to me anyway !
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David Forbes <dforbes@...>
At 8:12 AM -0700 4/2/02, ptsearcher2001 wrote:
--- In NEONIXIE-L@y..., David Forbes <dforbes@a...> wrote:The problem is that the tube's life decreases by much more than a factor ofI believe that they typically use about 2-3 times theYes and no! I meant the impulse current is a few times higher! 6 when you raise the current by a factor of 6... it decreases by a factor of 6^3.3, which is 370. Still, it will be on only 1/6 the time, so the lifetime decrease would be effectively 370/6 = 60, or an average lifetime of about 1000 hours. That's how long a regular house light bulb lasts, which is way too short to be practical in a clock. The other consideration is that you don't need that much current to obtain a decent display. Nixie tubes are very bright for indoor use. I find a naked Nixie tube to be too bright to be easily readable. --David Forbes, Tucson, AZ http://www.cathodecorner.com/
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Raymond Weisling <fire.mountain@...>
##### level-1 quote by fixitsan2002 (on) 02.04.02 (at) 15:27 +0000
> ...it begs a side-by-side A-B test, both of nixies andI am not talking about lifetime. I was referring to the peak current or on-state current required at a duty cycle of X percent on, to achieve the same apparent intensity. This is solely psycho-optical and can be completed for a given subject in a very short time. This was to prove or refute statements made about (for example) 1/6 duty requiring 6x current to achieve the same apparent intensity, either in a nixie or in a LED (they may not be the same, and in a LED it might even vary with the colour). Ray
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"fixitsan2002" <fixitsan@...>
--- In NEONIXIE-L@y..., Raymond Weisling <fire.mountain@p...> wrote:
##### level-1 quote by fixitsan2002 (on) 02.04.02 (at) 15:27 +0000is> ...it begs a side-by-side A-B test, both of nixies and themsubject to a variable duty cycle and variable current. Adjust currentfor identical apparent intensities, and do so at different it?levels for the DC drive one as the "standard". Who wants to do currentI am not talking about lifetime. I was referring to the peak or on-state current required at a duty cycle of X percent on, toOh alright, I misunderstood, I was going by the message title and should know it changes quickly here. True now, it would be interesting. Nevertheless, I'm still busy !
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"james10952001" <jamessweet@...>
In my first clock (non-multiplexed, discreet CMOS) I used much larger
resistors than recommended, the tubes are B-5870ST's IIRC running at around 300v with 100k resistors. I tried using 47k resistors and the tubes got slightly warm but weren't much brighter. --- In NEONIXIE-L@y..., "fixitsan2002" <fixitsan@a...> wrote: --- In NEONIXIE-L@y..., Raymond Weisling <fire.mountain@p...> wrote:timesOdd. My experience shows that you don't need anywhere near 6 thethecurrent to achieve a usable display; on the contrary, 6 times currentnonlinear.comes intowould cause the tubes to act funny. beeither. surprisedandat what you find.This is good -- it begs a side-by-side A-B test, both of nixies themLEDs. One of the devices is run at a DC current and the other is currentfor identical apparent intensities, and do so at different forlevels for the DC drive one as the "standard". Who wants to do it?Not me. (assuming we are looking for which method provides maximum 1/6th of its life whereas the direct drive is always on.(assumingyou never turn of the display)is dimmer, dont we mean 'cant ever be as bright as the brightest of
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"Nigel" <nigel@...>
I decided to do some quick tests in response to
Ray's suggestion. I had the beginnings of my first Nixie clock with 6 ZM1040's
wired up as a multiplexed arrangement driven off a PIC with transistor anode and
cathode drivers. By disconnecting the anode on one of the Nixies and feeding it
from a resistor straight from the HV supply I was able to do a direct comparison
between that Nixie and the remaining Nixies which were still
multiplexed.
I adjusted the series resistor until the
non-multiplexed Nixie gave the same apparent brightness as the multiplexed
Nixies and these are the results.
HV supply = 220V
Multiplexed Nixies:
Anode resistor = 15K V drop across resistor = 76V Anode current = 5mA Non-multiplexed Nixie:
Anode resistor = 133K
V drop across resistor = 95V Anode current = 0.7mA So the current required on the multiplexed Nixies
to achieve the same apparent brightness is about 7 times which allowing for
experimental error probably equates to the 6 times one might have
thought.
One thing I did notice was that, at the same
brightness level, the non-multiplexed Nixie appeared to give a 'thicker' or even
slightly fuzzy display compared to the multiplexed Nixie. I initially thought it
was a variation between devices so I swapped over the digits to make sure it
wasn't that.
I must stress that these tests were done quite
quickly, I would welcome hearing other people's observations.
I'm off to Las Vegas now for 2 weeks (working
not playing!) so probably won't be able to reply to any posts but I will
endeavour to keep looking at this group while I'm out there.
Nigel.
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"fixitsan2002" <fixitsan@...>
Fine bit of work Nigel.
I'm more intereted in muxing frequency myself. On many a data sheet, e.g. Z568, the max current for pulsed operation is 25mA. But it doesnt mention pulse duration sadly. However of the ones that do, 100-200uS seems to be average. I was at one time running at 100uS but some bad electronics made me slow things down to ten times that figure, 1mS. As far as brightness goes there wasnt a great deal of difference. Remembering that as you increase the ontime you decrease the refresh rate. But before anyone asks I have no idea what the best frequency is, there must be an ideal one. At 150uS and 25mA theres a slight ringing from Z568 but you would expect that. It was about equivalent to the brightness of 6mA of constant DC. So thats a factor of 4. Interestingly now, if I run at 25mA with a 1mS ontime, Its as bright as about 8mA DC, a factor of about 3. What I'm saying is we havent got the objectiveness of this sorted out enough have we ? Does anyone have any old design sheets which might give a clue of any 'ball park' muxing specs, if ever there were any. If we could establish something steadfast and solid we'll have a definitive answer to all of this. Until then..... --- In NEONIXIE-L@y..., "Nigel" <nigel@n...> wrote: I decided to do some quick tests in response to Ray's suggestion. Ihad the beginnings of my first Nixie clock with 6 ZM1040's wired up as a multiplexed arrangement driven off a PIC with transistor anode and cathode drivers. By disconnecting the anode on one of the Nixies and feeding it from a resistor straight from the HV supply I was able to do a direct comparison between that Nixie and the remaining Nixies which were still multiplexed. the same apparent brightness as the multiplexed Nixies and these are the results. same apparent brightness is about 7 times which allowing for experimental error probably equates to the 6 times one might have thought. non-multiplexed Nixie appeared to give a 'thicker' or even slightly fuzzy display compared to the multiplexed Nixie. I initially thought it was a variation between devices so I swapped over the digits to make sure it wasn't that. welcome hearing other people's observations. probably won't be able to reply to any posts but I will endeavour to keep looking at this group while I'm out there. times the >current to achieve a usable display; on the contrary, 6 timesthe current >would cause the tubes to act funny.comes into >play here, which makes the bightness-vs-duty-cycle curvenonlinear. >either. >For example, a typical 8-digit LED calculator certainly does NOTrequire >100 milliamps per segment - if it did, then the batteries wouldlast only >15 minutes! I believe that they typically use about 2-3 times theneeded is >to take a Nixie tube and run it at a fractional duty cycle, thenvary the >current with a variable resistor and look at the tube. You maybe surprised >at what you find.and LEDs. One of the devices is run at a DC current and the other isthem for identical apparent intensities, and do so at differentcurrent levels for the DC drive one as the "standard". Who wants to do it?the eye will likely exhibit different time-decay persistencephenomenon depending on the amount of visual purple and whether thereceptors are predominantly rods or cones.Service.
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"fixitsan2002" <fixitsan@...>
--- In NEONIXIE-L@y..., "fixitsan2002" <fixitsan@a...> wrote:
Fine bit of work Nigel.operation is 25mA. But it doesnt mention pulse duration sadly. I meant to say, there is a max current spec for pulsed operation, and the Z568 is 25mA
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Raymond Weisling <fire.mountain@...>
##### level-1 quote by fixitsan2002 (on) 03.04.02 (at) 16:26 +0000
On many a data sheet, e.g. Z568, the max current for pulsed operationNote that even though the duty cycle may be 1/6 (15% or so, allowing for some all-off time to kill ghosting), the pulse duration is not freely scalable. If data sheets list 100-200 us, then it may be safe at that range, but not with that current at 1 ms. Obviously one second in and five off would damage the tubes quite quickly, so the relationship is not linear. I find Nigel's information about crispness (focus) interesting. I noticed this as well when I was working on the built-in segment test mode for the Four Letter Word (B-7971 tubes). The test turns on only one segment at a time, one tube at a time, so with 15 segments there are 60 phases. At first the software look was very fast and they looked steady, but quite dim (and very uniform all along the segment). Even at such low intensity, the line was crisp and uniform. That is 1/60 duty. (In the end the test is slowed way down so you can watch the sequence, but there are several speeds selectable.) Ray
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"fixitsan2002" <fixitsan@...>
--- In NEONIXIE-L@y..., Raymond Weisling <fire.mountain@p...> wrote:
test mode for the Four Letter Word (B-7971 tubes). The test turns ononly one segment at a time, one tube at a time, so with 15 segmentsthere are 60 phases. At first the software look was very fast and theyuniform. That is 1/60 duty. (In the end the test is slowed way down so youcan watch the sequence, but there are several speeds selectable.)You're saying that you noticed it was not as crisp or that it was crisper ? I've found some frequency/current combinations which make the neon look like it is almost being sprayed away from the digit, sometimes at lower current but higher frequency than when the digit is crisp. I keep trying to make the digits go in and out of focus with a bit of success. Not useful to man or beast right now and I'm from the minimalist camp as far as controls go, but I know a few folk who would enjoy the idea of a clock with a focus control. All sober people too !
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Raymond Weisling <fire.mountain@...>
##### level-1 quote by fixitsan2002 (on) 03.04.02 (at) 17:09 +0000
You're saying that you noticed it was not as crisp or that it wasFar more crisp at the pulsed mode than when steady. Both were with rather conservative currents to the anode (of course the same resistors -- it is just a self-test mode that is selected by some of the six user-preference DIP switches; with so many segments and components involved -- 60 MPSA42 transistors and base resistors, 8 shift registers -- such a test mode is useful to locate problems). I find your de-focused, spray-effect intriguing. I wonder why it occurs. It is almost suggesting that certain frequencies of on-off ionisation, or thermal effects of same, have some resonating effect with the atoms or electrons. Hmmm. Another thing to investigate, eh? Ray
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