CO2 Power Supply Schematic Help

[djQUAN]

can you show a pic of how you made it?

 

[upaa27]

I think I need a cap

 

[djQUAN]

It looks ok but could also be that the hanging wires (sharp points) are creating corona discharges to the air? which could reduce the HV output.

 

[The Lightning Stalker]

Yes, you need a cap. If it won't charge a
cap, that will also tell you weather one of
the diodes is bad.

 

[Polonium210]

I think I need a cap

Thats a pretty scary wiring job for HV

 

[upaa27]

Thanks for your replies!

Insulated the wire before I left to go use the lathe but I will hook up some caps when I get back

 

[Sigurthr]

@ Po210, yeah, I had the same thought. But at the same time, it's a non-lethal supply before caps are added, so it is -only- scary, right now.

 

[upaa27]

My insulation basically involved wrapping a sht ton of electrical tape around all the eposed leads. When turned on with no caps tube is only seen flickering with lights off. HOWEVER it is going through the bore which is great!

Also, don't worry I won't discharge any caps through myself.

 

[The Lightning Stalker]

I hope you soldered everything first. The
solder won't stick once that adhesive gets
on everything.

 

[upaa27]

Hooked up caps in parallel so they could take more voltage. Wrapped connections a lot and turned it on. Caps made a loud screeching noise and I saw the caps were going through the tape. Carefully modified the setup using rubber gloves and the one hand technique and got similar result on the other cap. Shut everything off and didn't touch the caps and left.

I might just buy a psu if the rectifier keeps failing to keep the tube ignited. I'm not going anywhere near caps with hv anytime soon. I dread having to remove them from my setup.

Thanks for your help guys. I understand your concern now.

 

[Sigurthr]

Hooked up caps in parallel so they could take more voltage.

Series increases the voltage rating, not parallel. Parallel increases the current handling capability.

 

[upaa27]

I got the discharge down the bore finally! Redid all the connections, insulated until no more crackling and replaced the mineral oil with tap water. However as I do not own a co2 lpm my only reference to power is "burning" and compared to multiple videos I have seen, my laser is not putting out its maximum power.

Does going 8ma over really make that much of a change in output? I will probably add a potentiometer as a ballast resistor to see if that will help with output. I also still have to find some better caps as I don't think that 3 2200 pf in series will be able to sustain the output in the downtimes of the rectifier.

This is about the best it does to wood.

:thanks: for all your guys's help!

 

[Sigurthr]

At least we know the tube is good now!

The output is low just because you're running off of poorly filtered DC.
Vripple in Vp-p = I / 2 F C
We can assume about 30KHz for F worst scenario (15KHz on full wave rectifier), C is 2200 / 3 (series) or 733pF, what was the current rating of that electronic nst again? Sorry, I'd look but the huge pics make it hard to scroll this thread.

Enter into a calculator this: 0.0XX / 0.00004398
where 0.0XX is the nst current in AMPs (1mA = 0.001A).

That'l output the voltage of the ripple, or how many volts the output sags in between dc pulses. The caveat is that since there is no output current regulation after the smoothing capacitor you're probably getting a far more wild voltage ripple, as tube current is probably much higher during pulse times. Using a guesstimate of 30mA nst rating you're at best seeing less than 100V of ripple, not enough to extinguish the tube in between pulses. Even at 10x that I don't know the tube is extinguishing between pulses. You'd have to play around with anode resistors to improve performance.

The long and short of it; a professional 40W CO2 PSU costs about $100 shipped on eBay.

 

[upaa27]

At least we know the tube is good now!

The output is low just because you're running off of poorly filtered DC.
Vripple in Vp-p = I / 2 F C
We can assume about 30KHz for F worst scenario (15KHz on full wave rectifier), C is 2200 / 3 (series) or 733pF, what was the current rating of that electronic nst again? Sorry, I'd look but the huge pics make it hard to scroll this thread.

Enter into a calculator this: 0.0XX / 0.00004398
where 0.0XX is the nst current in AMPs (1mA = 0.001A).

That'l output the voltage of the ripple, or how many volts the output sags in between dc pulses. The caveat is that since there is no output current regulation after the smoothing capacitor you're probably getting a far more wild voltage ripple, as tube current is probably much higher during pulse times. Using a guesstimate of 30mA nst rating you're at best seeing less than 100V of ripple, not enough to extinguish the tube in between pulses. Even at 10x that I don't know the tube is extinguishing between pulses. You'd have to play around with anode resistors to improve performance.

The long and short of it; a professional 40W CO2 PSU costs about $100 shipped on eBay.

Only around 68v of voltage sag counting smoothing caps, but smoothing caps are NOT on it yet. I will also try to make the pics smaller sorry. I think I will play around with resistors a bit as I have quite a few and hopefully get 50w out. I might just put 10k ohm and increase from there.

The a laser psu is on my list though as I plan to continue on this path just I want to play around with how one works first.

Thanks sig.

EDIT: just tried 10k. It decreased output. Am I doing something wrong?

 

[Sigurthr]

Don't use a resistor without the smoothing caps. I didn't realize the caps weren't on yet, my bad! Put the caps on! Without the caps you're limited to 50% power.

 

[djQUAN]

I will probably add a potentiometer as a ballast resistor to see if that will help with output.

Don't! Pots have limited power dissipation and withstanding voltage rating. It'll burn up, arc over and/or electrocute you when you touch the shaft.