Burroughs B7971 Nixie Lifespans

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Fran Blanche

Fran Blanche

Күн бұрын

Пікірлер: 36
@gregorypeetros1083
@gregorypeetros1083 15 күн бұрын
Fran....If these tubes are driven correctly and to spec they will last forever. I have (5) 6 digit and (2) 4 digit B-7971 clocks that have been running essentially 24 x 7 for well over 15 years with no issues, degredation or loss of brightness. Considering these tubes are pulls from the stock brokerage displays and who knows how many hours they had on them before those displays were de-commissioned, I consider them some of the most robust Nixies out there. I have no issues with the tubes getting hot or even warm for that matter. I think once you have your design with individual cathode current regulation you'll see a big difference. Finally, I know of others that have been running these tubes 24 x 7 since the mid 70's without issue. Good luck and can't wait to see what you come up with.
@klaust.2769
@klaust.2769 15 күн бұрын
You are right! My Datasheet says max. 21mA current if all segments are lighted. This is in theory a dissipation of 3.57W at 170V for the whole tube. In real world it will be much less because the voltage drops if the segment has ignited. There are different currents for the individual segments. For a long live it will be good to run not more than 4 mA through each Segment.
@volvo09
@volvo09 15 күн бұрын
I'm going to have to look up a picture of that stock market sign. I never even knew tubes like this existed.
@gregebert3103
@gregebert3103 15 күн бұрын
You need TWO current limiters based on the B7971 datasheet information. As you mentioned, each cathode needs the current limited; I use an NPN transistor with a resistor at the emitter, to limit the current. The base is driven from a known voltage, say 3.3V, and the base-emitter voltage is 0.7V. So, to control the current, select a resistor value RE=(3.3-0.7)/current. The smallest segments require 4mA, so their resistor will be ~650 ohms. The remaining segments need 5.0,5.5, or 6.0mA so their resistors will be 520, 470, or 430 ohms. Now, the second current limiter is required because the max current of ALL cathodes combined must be 21mA or less. So, at the anode side, you need a similar current limiter. I use a PNP transistor. It sounds like a lot of extra cost and hassle, but electronic components are essentially free and in unlimited supply, whereas B7971 tubes are getting very expensive (typically 200USD each), and increasingly harder to find. It will take time to find a set of 6. Glad I got mine (and a few others) years ago.
@FranLab
@FranLab 15 күн бұрын
All true. I did assess all the options, particularly with the various differences in optimal segment current, as the slightly shorter cathodes need more limiting, etc... I will get around to rebuilding it - and I have many other tubes, so I wasn't worried about putting wear on this one, but my bigger project requires an array of proper driver boards.
@gregebert3103
@gregebert3103 15 күн бұрын
@@FranLab As others have pointed out, 7971's are durable tubes. My 8-tube clock has been running since 2017, and the only failure I've had is shorting between 2 segments because they can actually get dislodged. Expect many years of usage when you make your clock, and be sure to use a passive-IR sensor to shut the tubes off when nobody is there to watch the clock (I run a walking pattern on all segments). Also, I recommend direct-drive, rather than multiplexing. If you'd rather plug your tubes into a proven design, there are some good kits out there (MOD-6, Lumina) for the 7971.
@gwesco
@gwesco 15 күн бұрын
About 50 years ago, the local Burstein-Applebee store carried a bit of surplus and I bought a bunch of those boards for $5 each! I built a nixie clock out of 6 tubes and it ran for over 20 years before I replaced it with a smaller nixie clock using the Russian tubes. Some day I may have to plug the big clock back in to see if it still works.
@Scott-s9u3n
@Scott-s9u3n 10 күн бұрын
There was ( is?) an old nixie tube clock at my last job that had been on continuously for 27 years. I had a vacuum fluorescent display clock radio that had been in use about 17 years before it got " borrowed" by a relative. I currently have an old mechanical digital clock with a NE2 dial light that still works after 46 years...
@Jack_Luck.v2
@Jack_Luck.v2 15 күн бұрын
Im going to need the Fran Lab theme song, i think it is badass. Good to see you again. KZbin apparently thinks that when you follow people, you dont actually want to see their content Helium degradation is a problem with Neutron Detectors, some have helium in them, and over time, they will lose that helium. Others dont contain helium, but when you're using surplus equipment, even NOS, you get tubes that magically add more helium to their interior atmosphere. Rip tube. Lol
@jeffreyyoung4104
@jeffreyyoung4104 15 күн бұрын
It reminds me of my first LED 7 segment display where I only had one current limit resistor, and the display dimmed more when more segments lit. After I redid the circuit to have each segment limited, the display remained bright no matter how many segments lit. The best bright display is when you can multiplex the display, and run more current for a short time, and your vision persistence makes up for the off time. Do you have the background grounded or floating? If it is grounded, perhaps it attracts the electrons, which causes the bleaching? As far as helium goes, it is able to leak past seals and threaded joints. which means it doesn't have to travel through material except under the high pressure conditions.
@bit-tuber8126
@bit-tuber8126 13 күн бұрын
About that plasma fade, rember the phosphor screen burn in of old computer CRT screens?
@robjennings3045
@robjennings3045 15 күн бұрын
The data sheet gives you the current limit per segment and you really should follow that. One resistor per segment is more components on the PCB but the tube will "last forever" with a better even brightness. If the white area is growing significantly you are likely over driving in general. I have a clock running for years and seen no change in the tubes and they are never hot or even warm to touch. Standard numeric nixie tubes will also specify current drive per numeral as the different sizes have different demands, most designs also ignore that requirement.
@LutzSchafer
@LutzSchafer 15 күн бұрын
Fran I guess you got carried away a little with the helium. Never heard any story that vacuum tubes get contaminated with helium. It's usually the cathode losing emission over time. Going on air is most likely due to failing seals I would think. The getter will try to counter this but there is only so much available....
@saucerjock
@saucerjock 14 күн бұрын
200v for a digital readout? Fts. I like your breadboarding. The physical mechanical structure is sollid. But still, 200v? How much you got running between the cathode and anode? You could just be vacuum plating everything. What I remember about tubes is inverse distance on the beam flow. Probably tungsten. Don't cross the beams. Any way to reverse the process? You'd get a very clean shiny tube.
@KeritechElectronics
@KeritechElectronics 15 күн бұрын
I'd look into controlling them with two SN75468 drivers for the cathode side.
@stuartmcconnachie
@stuartmcconnachie 15 күн бұрын
Or a TPIC6B595 shift register. Considerably simplifies the wiring back to the microcontroller as you can drive a virtually infinite number of daisy-chained displays without the need for any extra microcontroller outputs, or any multiplexing of the tubes. Then just a single currently limiting resistor on each segment, rated according to the segment size and recommended maximum current as given in the B7971 datasheet. This is my much preferred way of driving these tubes. Plus add a boost converter to generate the 170v DC, and then you can run everything from a single 12v DC supply.
@KeritechElectronics
@KeritechElectronics 15 күн бұрын
@@stuartmcconnachie cool, I'm only worried about the max Vds of this chip being 50V. Seems a bit low for me. That's why I'd combine a 74HC595 with SN75468.
@stuartmcconnachie
@stuartmcconnachie 15 күн бұрын
@@KeritechElectronics Works just fine. The outputs of the 6B595 are diode clamped at the 50v to provide transient protection for driving relays, motors, etc. So the voltage drop across the segment when off is your anode voltage less 50v, or 170 - 50 = 120v. Not enough to reach the strike voltage, so the segment doesn’t illuminate. And unless the segment is actually illuminated, zero (or virtually zero) current will actually flow. I think it was Dave Jones who used these in his Nixie project, although granted they weren’t B7971 tubes.
@KeritechElectronics
@KeritechElectronics 15 күн бұрын
@@stuartmcconnachie he definitely used IN-12 tubes for his subscriber counter silver button project, but I'm not sure if he did other nixie projects.
@stuartmcconnachie
@stuartmcconnachie 15 күн бұрын
@ No, but principle is the same regardless of tube type. I have used 6B595 to drive my IN18 clock and B7971 FLW projects here for several years. About the only downside is they use 5v logic, and so can be driven directly from lower voltage microcontrollers (I use 3.3v ESP here). But if Fran is using a 5v Arduino that issue would go away.
@HamburgerAmy
@HamburgerAmy 15 күн бұрын
♪ ♫ ♬dun dundun ♪ ♫ ♬ ........it's fran... ♪ ♫ ♬......in the lab. franlab.
@Scott-s9u3n
@Scott-s9u3n 10 күн бұрын
I would guess they have the lifespan of a neon indicator bulb... I think you just explained why some neon bulbs darken over time... something I wondered about..
@stuartmcconnachie
@stuartmcconnachie 15 күн бұрын
2:00 “Complicated driver”? It’s literally just a single current limiting resistor on each segment, as indeed you later say! Using a suitable open collector shift register as the driver and you can get rid of those transistors. My B7971 never get even vaguely warm, let alone hot. As others have said these tubes will last for decades or more if correctly driven. They certainly don’t need to be driven hard for domestic use, as was probably the case in their original installations.
@randycarter2001
@randycarter2001 15 күн бұрын
Good old Ben had part of it right. He knew something flowed in the circuits, but he didn't know what and which direction. So Ben called it charge and it flowed from positive to negative. He had a 50/50 chance and he got it wrong. Somebody figured out later it was electrons and they flowed the other way. But, by then all of the charge flow theories had already been established.
@wmrg1057
@wmrg1057 15 күн бұрын
Helium has left the room
@D.E.Middleton
@D.E.Middleton 15 күн бұрын
Thanks Fran..
@gordonlawrence1448
@gordonlawrence1448 15 күн бұрын
Hi Fran, with all the numbering malarky, how did you stop your brain turning to porridge?
@FranLab
@FranLab 15 күн бұрын
Based on some comments it seems that perhaps I did not!
@XanCraft21
@XanCraft21 14 күн бұрын
For some reason i always thought that animated background display was a numitron display. I feel so silly now. 😮
@joehopfield
@joehopfield 4 күн бұрын
I read "Bigass" as "BigGlass Alpha..."
@mariomionskowski6223
@mariomionskowski6223 15 күн бұрын
IT IS called defusion, what the Helium does.
@patrickcardon1643
@patrickcardon1643 14 күн бұрын
We need a Helium cartoon 😁 poopidoopidoo
@TrinomCZ
@TrinomCZ 15 күн бұрын
You could probably alter the base resistors and limit the current using amplification of the transistors.
@fo4mm209
@fo4mm209 15 күн бұрын
interesting 👍
@filepz629
@filepz629 15 күн бұрын
❤️‍🔥FRAN❤️‍🔥
@youtuuba
@youtuuba 15 күн бұрын
Fran, you playing with that noise machine machine in your recent videos is VERY irritating; I hope you discontinue that trend.....
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