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FrozenGate by Avery

CO2 power supply

Pontiacg5

Pontiacg5

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Alright, I want to build another CO2 laser, but this one I want to build right.

I would like for it to be DC powered, 12V to be exact. I'm thinking a neon sign transformer through a voltage multiplier to the voltage I need. I'm looking at something on instructables based on a villard doubler, its basically a ladder with each step having 2 diodes and 2 capacitors. I think the current stays the same through each step, so if i find a power supply that runs at 25mA I think I should be good.

The tube I think I'm getting runs at 16kv and kicks on at 22kv. Would, or should, I have a capacitor to "start" the tube and then just power to keep it running to keep the excess volts away or is this necessary? I was thinking about having my "multiplier ladder" a "rung" longer to charge a capacitor to fire the tube at first. Then the laser could run off of the next lower rung to keep voltage down, right?

I would like to be able to measure the high voltage current and voltage, but how would I do that? I was thinking resistors, but that would lower either voltage or current. Then I thought I could compensate for that loss but how do I know what to compensate? Then I thought I was thinking too much and I should ask for help, so that's what I'm doing :)

I really don't know where to start. I know how to make a tube run, but I want it to run right. Am I at least somewhat on the right track?
 





A voltage multiplier will not keep current constant. If it did you'd have some magical power creating device ;)

If you increase voltage, current will drecrease.

You will probably have to run it like a HeNe tube, with a large ignition pulse followed by a constant supply at a lower voltage. For HeNes it's usually accomplished with a ballast resistor. You'll probably want to look into a flyback transformer to generate the HV, that's what I've seen used in commercial CO2 laser power supplies.
 
The way you might want to go is a Cockcroft-Walton voltage multiplier with a parasitic
multiplier. I don't have a schematic, but it would be a hell of a build if you want to power
it from 12VDC. If you could power it from mains or an inverter, then it could be very simple.
[Edit: A neon sign transformer was what I had in mind, and I somehow missed what you had
said]

Regards

Lachlan
 
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That would be something like this right? This is the ladder I was talking about, except there's a couple of resistors I didn't plan on having. Is this what makes it a parasitic multiplier? I guess it makes sense, but I think I'm missing how exactly it works.

So the resistors will let the tube start, but once the tube starts and resistance goes down the resistors limit the voltage to the running voltage right?
 
I can't find out how much current is lost in each step, Is there a formula to figure this out?
 
C-W multipliers double the voltage at each "step" in the ladder. They also cut the current in half at each one. Since nothing is perfectly efficient, you lose a little extra current in the components and wiring as heat. These losses are usually very small though.
 
Alright, that's what I was thinking.

Now what is the difference between a half wave and full wave? I'm guessing that a half wave is pulsed output, but full is not, right?
 
Pontiacg5 said:
Alright, that's what I was thinking.

Now what is the difference between a half wave and full wave? I'm guessing that a half wave is pulsed output, but full is not, right?
Click to expand...

A half wave rectifier conducts half of the time.The dc output is at half the input frequency, since only 180 degrees of the input waveform gets used.A full wave rectifier outputs over the entire 360 degrees, but as the source ac waveform crosses the zero point, the output of the full wave also crosses zero.IE: both output pulsed DC.
What this means in very simple terms is this:A full wave rectifier needs less filtering to get pure dc than a half wave.
I hope this helps, if it is only confusing I can point you towards the references you need to build your own power supply.
 
Some references couldn't hurt, but I think I understand. Since I plan on a DC input, a full wave would not do me much good, right? Unless I had 2 pulsed input voltages, one on while the other was off.
I think a CO2 tube would be alright with a pulsed input, so I shouldn't have to worry about filtering it too much. I would only assume that I wouldn't get as much power out of the tube as I could.

I think I will ask for those references if you don't mind :D
 
Pontiacg5 said:
Some references couldn't hurt, but I think I understand. Since I plan on a DC input, a full wave would not do me much good, right? Unless I had 2 pulsed input voltages, one on while the other was off.
I think a CO2 tube would be alright with a pulsed input, so I shouldn't have to worry about filtering it too much. I would only assume that I wouldn't get as much power out of the tube as I could.

I think I will ask for those references if you don't mind :D
Click to expand...

Hey

If this is a portable one then a flyback would be fine for driving the tube they produse pulsed dc wich is the same way my co2 psu works , is this was not portable then you could use a NST and recifer , the tubes work on DC pulsed or smooth fine , :)

For ac to dc , full wave rectifer will give you ---------- Dc and half wave will give you - - - - - -

Not the best example but u can see in the half wave you loss half of the ac wave . If that makes sense , Would be hard to smooth 10 - 20 kv to run the tube , flue wave would be fine to run it with out smoothing , as i said flyback drivers produse pulsed DC over 20Khz or somthing like that .

Ion
 
ionlaser555 said:
Hey

If this is a portable one then a flyback would be fine for driving the tube they produse pulsed dc wich is the same way my co2 psu works , is this was not portable then you could use a NST and recifer , the tubes work on DC pulsed or smooth fine , :)

For ac to dc , full wave rectifer will give you ---------- Dc and half wave will give you - - - - - -

Not the best example but u can see in the half wave you loss half of the ac wave . If that makes sense , Would be hard to smooth 10 - 20 kv to run the tube , flue wave would be fine to run it with out smoothing , as i said flyback drivers produse pulsed DC over 20Khz or somthing like that .

Ion
Click to expand...

I've seen how to's on the internet to make drivers for the flyback transformer out of CRT monitors and tube TV's. All you need to do is pulse the DC input and you get pulsed DC output, right? But can a flyback from a TV produce enough current without too much voltage? I had to use 2 flybacks to run a 20W tube the last time I tried, so maybe I just need a bigger flyback. And if I'm going to rig something together like this couldn't I use automotive coils? I think they might be a little easier to handle.
 
Pontiacg5 said:
Some references couldn't hurt, but I think I understand. Since I plan on a DC input, a full wave would not do me much good, right? Unless I had 2 pulsed input voltages, one on while the other was off.
I think a CO2 tube would be alright with a pulsed input, so I shouldn't have to worry about filtering it too much. I would only assume that I wouldn't get as much power out of the tube as I could.

I think I will ask for those references if you don't mind :D
Click to expand...

The amateur radio handbook has all the basic stuff you will need.Check it out of your library to avoid spending money on it.
A portable unit will be heavy and bulky probably.A microwave oven transformer with a rewound primary and a voltage tripler circuit would work.But it will be heavy.
But cheap!
 
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