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Spasticteapot 18th October 2006 01:24 AM

El Cheapo HV source?
 
While looking for a cheapie tube transformer, I found an oddity: a 200:1 autotransformer for use with an ion generator.



http://www.alltronics.com/cgi-bin/it...%2DTransformer

I was wondering if a 120:25v transformer could be used to reduce the input voltage, producing (roughly) 4.8 Kv.

And it's 3$, too!

I_Forgot 18th October 2006 03:35 PM

That is a high frequency device. The core is ferrite. It would probably be pretty easy to make a driver- a 1 transistor oscillator using a power transistor, or a 555 driving a power transistor.

I bought some of the complete ion generators from Alltronics years ago when I lived in the Valley. They had barrels of them! I guess they are down to just pieces of them after all these years...

I put one of the ion generators near my cat's box to kill the odor. It worked, but after about a year I noticed that all the dust from the box ended up glued to the wall because of the ion generator.

I_F

stokessd 23rd October 2006 08:03 PM

Other sources of high voltage include low voltage transformers turned backwards (drive the secondary), and vacuum flourescent power supplies. small switching supplies for neon transformers.


The circuits from disposable cameras generate 300V DC from a single AA batttery. You could use the flyback transformer from several of them and build a voltage multiplier instead of the half wave bridge which would give you the high voltage you need. There's not much cheaper than "free". I don't know if the little flyback transformers would stand up to continuous use, but it's a pretty easy experiment to ask for a couple at your local photo place and play with them.

I did the backwards transformer thing to great effect in my ESL HV supplies.

Sheldon

stokessd 24th October 2006 12:26 AM

Here I am replying to my own post. I'd love to hear if anybody tries to use a disposable camera flash circuit for HV. I think with a voltage multiplier, that you could get 4KV from it with a voltage multiplier, and that's with the 1.5V power source. With say 3 volts or so, I bet you'd have as much voltage as you need.

I'd like to know if the little flyback will tolerate continuous duty.

Sheldon

Spasticteapot 24th October 2006 05:35 AM

Quote:

Originally posted by stokessd
Here I am replying to my own post. I'd love to hear if anybody tries to use a disposable camera flash circuit for HV. I think with a voltage multiplier, that you could get 4KV from it with a voltage multiplier, and that's with the 1.5V power source. With say 3 volts or so, I bet you'd have as much voltage as you need.

I'd like to know if the little flyback will tolerate continuous duty.

Sheldon

I think they'd just blow up under the draw.

DigitalJunkie 24th October 2006 05:47 AM

I've played with the little camera flash circuits from disposable cameras a few times..The one thing they don't seem to like is a higher input voltage. (oscillator transistor fries) 1.5-3V seems fine though.
I've used them to charge larger caps with(2Kuf),and i've let them run for quite a long time..they seem fairly robust for cheaply made little circuits.

I even made a tiny amp with one and a 3S4,a small OPT,and a headphone driver soldered right to the OPT pins.
The whole deal fit in the palm of my hand! ran off of 2x AA's.

I suspect they can't deliver a lot of current though.

(By the way,Hi Sheldon! :wave2: Havn't seen you around in a while. )

ak_47_boy 25th October 2006 10:32 PM

A microwave oven transformer makes 2kv? Huge current though :(

stokessd 25th October 2006 11:38 PM

Quote:

Originally posted by ak_47_boy
A microwave oven transformer makes 2kv? Huge current though :(

I wouldn't do that. The HV supply being small also makes it non-lethal. Not so with a 2KV 1000watt supply.


Don't forget that you need practically zero current.

If you want to go cheap and simple. by 4 filament or power supply transformers with split primaries (120-240 volt jobbies). Run the first one just as the manufacturer intended, which should be putting out your low voltage AC. Then hook the other three up backwards with their secondaries all attached to the powered one's secondary. The primaries (now the secondaries) will have about the line voltage on each half of the primary winding. Hook all 6 primary windings up in series (minding polarity), and you've got about 600V AC. Now build yourself a cockroft walton voltage multiplier out of 8 diodes and 8 caps and you've got a simple HV supply. No adjustability, but hard to beat the price if you can find surplus small transformers. The beauty is that the secondary voltage really doesn't matter as long as they are all the same (to avoid core saturation). That makes it easy to find surplus transformers when you can take about anything.

It's not particularly small or light, but it's cheap and will work quite well.

Sheldon


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