Co2 laser powered by zvs driver?

[Pieznice29]

Thanks i Reckon i can get a lot more power out of it, i just need a better power supply for my driver. My current method for checking tube current doesnt really seem to be working, my meter is jumping all over the place so im a bit worried about putting too much current in though...

 

[anselm]

Great!
So I reckon the gas is sealed inside, it's a permanent filling that keeps regenerating itself?
Make sure you cool it plenty, you wouldn't want that glass to crack now, would you?

First step to become an evil mad scientist.

 

[Pieznice29]

@anselm:
Yeah its a sealed tube, makes it sooo much easier.
Currently im using the syphon effect to keep water flowing through the tube, havent got a pump yet. It seems to keep it fairly cool for short runs. (less than a minute or so)
Haha yeah Now all i need is a big jacobs ladder to go with it and i'll have the set

@Everyone:
I got my current meter working, in my latest video its running about 7ma or so. The tube is rated for 18ma so ive got quite a bit of power left to use :evil:

Latest video

 

[plexus]

very very nice. i have been "eyeing" these tubes for awhile. one of my concerns is the integrity of the glued components (as opposed to hard sealing). i wonder how good the "soft sealing" is on these?

 

[Arayan]

Very nice I doubted because the frequency of the zvs is normally high, and the current is low, while CO2 tubes work with smooth DC.

 

[Pieznice29]

@Plexus:
From what ive heard the tubes tend to leak a lot faster compared to the hard sealed type. The manufacturers rate them at 80% output power after 3 months of storage from what ive found. A hard sealed tube will probably last much longer than this, but of course they are far too expensive for me

@Arayan:
The co2 laser seems to work quite well from my zvs + flyback transformer supply even without any filtering other than half wave rectification (flyback has internal diode). When i ran the zvs driver from un-smoothed DC straight from a mains transformer the tube hummed at the AC frequency, and so did anything i burnt with it

 

[Arayan]

@Plexus:
From what ive heard the tubes tend to leak a lot faster compared to the hard sealed type. The manufacturers rate them at 80% output power after 3 months of storage from what ive found. A hard sealed tube will probably last much longer than this, but of course they are far too expensive for me

@Arayan:
The co2 laser seems to work quite well from my zvs + flyback transformer supply even without any filtering other than half wave rectification (flyback has internal diode). When i ran the zvs driver from un-smoothed DC straight from a mains transformer the tube hummed at the AC frequency, and so did anything i burnt with it

Great result for me
rep +1

 

[Pieznice29]

@Arayan:
Oooo, my first ever rep

 

[anselm]

not true

 

[james1095]

Makes sense that the power would be about double that of flyback mode, since you're driving the core push-pull and making full use of it.

Some CO2 tubes are quite happy on AC, and generally the higher the frequency the better. If the electrodes are symmetrical then AC is fine. If one electrode is large and the other is small, it's a DC tube and the small electrode *must* be the anode. DC-only tubes will be damaged by AC.

 

[Pieznice29]

Sorry anslem, didnt notice that

@james:
Yeah i worked out the tube polarity by the size of the electrodes. Whenever i play with HV DC i find the cathode always gets hotter than the anode, i assume the larger electrode in the tube is to provide more thermal mass/better cooling for the cathode?

 

[Cyparagon]

Here are a few problems I see with AC. If it is from a Neon sign transformer (A favorite among DIYers), the discharge is extinguished every half-cycle. If it is sinusoidal, the RMS values might look great, but peak power may be a bit much for different parts of the system. The discharge process produces CO and O2, which hinders lasing. In these sealed tubes, the DC helps circulate the gas so the CO can be recombined (I think water vapor is the catalyst for this)

 

[Benm]

You could add a (bridge) rectifier using hv diodes and if you can obtain it, a suitable capacitor. Diodes from microwave ovens come to mind as they are usually rated 10 kV or more, so a few in series would suffice for each end of the bridge.

Be careful with adding buffer capacitors though, those can zap you dead on a mistake.

 

[Cyparagon]

I don't think they're that high. The one I have is 2.2KV, but that was from a ~900W oven. Either way, you can stack a bunch of smaller ones.

 

[james1095]

I don't think they're that high. The one I have is 2.2KV, but that was from a ~900W oven. Either way, you can stack a bunch of smaller ones.

12kV diodes are common, at least for commercial microwave ovens, but the current ratings they have are vast overkill for this. Check out OT Electronics, they have some cheap HV diodes that will work nicely and I've bought from them before, no complaints. If you're running high frequency you don't need much capacitance, a few nF is enough to smooth it pretty well. They have some cheap 15kV ceramic capacitors as well, I worked on a dental xray head that used pairs of very similar caps in series as part of a cockroft-walton voltage multiplier to provide 70kV to the tube. For low current high frequency stuff, a voltage multiplier lets you use a much simpler lower voltage transformer, say 10kV and double it to 20kV for the laser tube.

 

[Pieznice29]

Thanks for the tips
I have a home made 10nf (ish) capacitor somewhere made from a vodka bottle and some foil which i normally use whenever i want smooth DC from a flyback transformer. I think my transformer has some internal capacitor, i have to discharge it before i touch it or i get a fairly nasty shock. Would adding a bridge rectifier help considerably? Right now my power supply is only half-wave rectified because of an internal diode.

I think I'll work on getting the tube up to full power before i worry about a smooth power supply. i can only get up to about 6ma right now. The power supply im using for my zvs driver can only do about 5A at 24v, from the looks of things i need at least double that.