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DIY HeNe PSU?

Wolfman29

Wolfman29

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Hey everyone - I recently got a little tiny 5" HeNe tube, and I am looking to make the smallest possible PSU to go with it (planning it for a handheld).

Anyone have any ideas on how I can drive this? I am looking for schematics, but I can't seem to find any except on Sam's Laser FAQ and his schematics are very difficult for me to read.

Anyway, I'm thinking something along the lines of a boost driver up to around 50V or something (I know some simple boost drivers can do that), followed by a voltage multiplier and then a ballast resistor, and I can add a pulse at start up with a 555 timer or something along those lines.

Does it sound like it could work?
 





Sigurthr

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HeNe tubes like 1000-1750V @ >3mA, even for small ones. You would need one hell of a voltage multiplier to get from 50V to 1250V, and lose a LOT of current in doing so.

I've never built one but I've seen it done by making a flyback driver and running it at the lowest voltage it will go and then filtering the output with HV capacitors and using a Zener Diode string (with lots of 100V zeners) to regulate the voltage and a HV resistor to limit current to the required level. It was NOT tiny nor cheap.

A simple low (or even operational level) voltage pulse is not enough to ignite the tube, typically you need either RF freqiencies at a couple of watts or a very high voltage pulse (>6000V) to start even a small tube.

IMO just buy a power supply, you can get a nice JDSU 12V brick for less than $40.
 
Wolfman29

Wolfman29

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I know - I figured I would construct the voltage multiplier such that it would have additional stages for said pulse - the 555 timer would simply be a trigger is all.

Anyway, I think I will undertake this project. I think the first place to start would be to obtain the smallest transformer I can for the highest turn ratio.
 
Sigurthr

Sigurthr

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It might be easier to rectify, filter, zener regulate, and current limit a small SMPS Neon Sign Power supply or small NST.

Heck, you could do it with a MOT but that is the antithesis of "small".
 
Wolfman29

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If I could find a small enough neon sign power supply, that would be awesome ^_^
 
T_Warne

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Wolfman29

Wolfman29

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I'm looking for something that is about as big as the tube itself. Possible 4-5 inches long at most and fitting in a tube about an inch in diameter.
 
T_Warne

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Finding something that will fit inside a 1" tube might be challenging. Here is something on a board that you might be able to reconfigure to meet your needs.
3,000 volts, 10 milliamps 2.5 " x 1 " x 1.25"
88_1_b.JPG

NEW NEON TRANSFORMER 3,000v 3KV clock speaker etc. | eBay

What output voltage and current do you need?
 
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Wolfman29

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Need about 1kV at 4.5mA for continuous and about an 8kV trigger. I'll take a look at that though... that looks small.
 
benmwv

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I think you could wind a transformer for that. Have a 12v input and wind 10:1000 or 20:2000. You could use a 555 plus transistor to drive the transformer then have a 3 stage multiplier to provide the trigger.
 
jeffreythe00

jeffreythe00

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I have some flybacks here if you need em. Dont know much about hene's but I have both DC and AC flybacks. Let me know if you need one. All of my flybacks are NEW and never used.
 
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jeffreythe00

jeffreythe00

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The AC flyback Is probably MUCH larger than you want. However the DC flybacks i have are not too large. If you change your mind just hit up my pm box :). Btw didnt forget about the xmas gift :p. Its on my giant list of things to do :)
 
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