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ArcticMyst Security by Avery
Powering a HeNe with an old CRT monitor
- Thread starter Cyparagon
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Pretty neat. I'm surprised it's lasing, I didn't think the flyback in a CRT could source enough current. Nice work sir, I learned something new today.
hakzaw1
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I am guessing this "PS" could be made much smaller--- could it power two HeNes like that? i have a pair that I want to make into lamps. these days you cant give away old monitors like that.
TY for sharing this-- hk
TY for sharing this-- hk
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Hell, it could power at least 4 of them in series. That's 25,000V or so. Not a good long-term idea though. I don't think the wave form is desirable.
Bluefan
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I can't find the ballast resistor, what keeps it stable? And those wires don't look like high voltage cables, be very carefull with them.
hakzaw1
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Guess I will forget that idea and look to find a good deal on two small brick PSs--what do they use to power them when they are inside of a barcode scanners that these old tubes usually come from?
thanks for any help,,,,,,,,,,,,,len
A HeNe tube needs very little current, a flyback would easily run a few and even larger ones.
You can remove the transformer from the monitor and build it a driver circuit, making it much smaller (And even more powerful).
Unlike some other gas lasers, you don't really need to worry about stability with HeNe's.
You can remove the transformer from the monitor and build it a driver circuit, making it much smaller (And even more powerful).
Unlike some other gas lasers, you don't really need to worry about stability with HeNe's.
Benm
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I think most monitor flybacks would put out much more power than a HeNe tube is supposed to handle. Perhaps its useful for testing purposes, but i doubt the tube would last very long.
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My previous impression was that a flyback transformer could only source a few hundred uA, not the 5-8 mA needed to run a HeNe. Though the voltage is definitely 10x higher than it needs to be. That extra energy must be going somewhere... does the tube get unusually hot running like this?
In many monitors, the flyback is part of the resonant circuit that includes the horizontal deflection. Newer monitors supporting a wide range of horizontal scan frequencies will have a separate circuit though. A HeNe tube will load down the output voltage to whatever the tube likes, with the current limited mostly by the DC resistance of the secondary winding. There is a good chance that the drive circuit will fail (sometimes quite spectacularly) otherwise the flyback will probably overheat eventually.
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You might notice in the picture I don't even have the anode lead connected. It's just sitting about an inch from the head there so the tube never sees the full voltage. I guess you could say my ballast resistor is oxygen/nitrogen based.
Something else just for fun:
Something else just for fun:
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Wow!!!
This I have to try! I happen to have a 20" TV that got recently retired from service. If I get my MG tube to lase, this will be an extremely cool experiment. So the flyback out is connected to the cathode and you're just waving the ground wire near the anode? Wouldn't there be some arcing?
- Robert
This I have to try! I happen to have a 20" TV that got recently retired from service. If I get my MG tube to lase, this will be an extremely cool experiment. So the flyback out is connected to the cathode and you're just waving the ground wire near the anode? Wouldn't there be some arcing?
- Robert
The output of the flyback is positive, so it would go to the anode of the tube. Yes, if you put a ground wire near anything it will arc.
I don't recommend doing this on a tube you care about. The peak voltage from the flyback is much higher than a HeNe tube requires. You can punch pinholes in the glass which will destroy the tube. I've done it to light bulbs before. The hole is microscopic but it lets air leak in.
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I have used a few flybacks to power HeNe's, and They provide plenty of juice! Did not use a monitor flyback, but TVs I think They might have a bit more umph. Actually it's a bit scary at 1st because the voltage is very high, and I just had them laying on the bench.
Hak You could use a flyback for the tube you have with no PS.
Hak You could use a flyback for the tube you have with no PS.
CRT computer monitors typically have a higher anode voltage, 25-35kV, while most TVs are in the 19-25kV range, but the TV flyback may be able to deliver more current as the screens are usually larger.
Yes, it will work, but you stand a good chance of damaging the tube or at least greatly reducing the life. HeNe tubes want a well regulated current source, and driving one with a TV flyback you don't really know what you're getting. For long term operation definitely use a proper power supply.
Yes, it will work, but you stand a good chance of damaging the tube or at least greatly reducing the life. HeNe tubes want a well regulated current source, and driving one with a TV flyback you don't really know what you're getting. For long term operation definitely use a proper power supply.
