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CO2 laser

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Shaun

Wed Feb 27 2008, 11:41PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Thanks for the data, plazmatron. As of now I have a single ZnSe lens (well I don't have it yet, but its on its way), and I'm keeping an eye out on Ebay for another one.

mikeselectricstuff

Fri Mar 14 2008, 11:57PM

Registered Member #311 Joined: Sun Mar 12 2006, 08:28PM
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Posts: 253

20-30w in a ballast resistor is not a problem if you have a water cooling circuit anyway....
You could also arrange for some of the ballasting to be on the low-voltage side of the PSU.

lpfthings

Sat Mar 22 2008, 11:45AM

Registered Member #1361 Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305

You are going to have a hard time getting optics for a co2 tube, since plastics absorb the laser, and just melt. Optics for c02 tubes are quite expensive. c02 tubes are just like photo flashes, in the fact that you need to send a pulse of power to ignite it (in yur case, 15kv), then drop it down to the operation level, otherwise it may overheat and melt itself. Be careful with co2 lasers, i have a friend on another forum that has a 60W co2, now that thing burns like crazy!! He can write in white toilet seats, burn wood, burn through books etc. Have fun!

Shaun

Sat Mar 22 2008, 03:01PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Oh, I am having fun. I'm still using a rectified 15kv 30ma NST for power, thought, because I'm haven't had much time to build a proper PSU yet.

My cheap DMM in series with the tube to keep an eye on current hasn't complained at all about the kilovolts through it, but then again ohms law says it shouldn't.
Cooling is a cheap fountain pump from the hardware store.

As for the lens, it works okay, but the focus is like 5mm from the lens surface, so its kind of inconvenient. I am trying to get another so I can get a continuous thinned beam.

ragnar

Sun Mar 23 2008, 11:58PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
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Posts: 1425

Shaun wrote ...

Thanks for the data, plazmatron. As of now I have a single ZnSe lens (well I don't have it yet, but its on its way), and I'm keeping an eye out on Ebay for another one.

Zinc sellinide is the right lens for IR; as for mirrors, polished gold is good. You can expect anywhere from a 1-10% loss in each of your optics. My 25W CO2 laser loses about 3% on each mirror, and 2% through the lens.

Carbon_Rod

Mon Mar 24 2008, 09:21AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Generally e-bay is a bad deal for CO2 tubes. You can get them surplus in the >100-250watt range for mush less $ with aligned optics intact. Note, aligning these things is not a trivial matter... and some surplus will mean they are already "burned-in" and ready for use.

If output stability and CW mode is not your intention, one could likely get away with a much simpler power supply (most need a large inline resister.) SAMs Laser FAQ will surely have reference designs.

Shaun

Mon Mar 24 2008, 03:41PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Where can you find these surplus lasers? and just how much cheaper than Ebay are they?

Conundrum

Mon Mar 24 2008, 04:03PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

hehe... i have a truly evil cunning plan.

In a dead >19" LCD TV you will find a very large power PCB with eight or so outputs for the cold cathode tubes.

If you connect the -V sides via resistors to ground and combine the +V outputs using HF capable (i.e. 1N4007) diode strings, you will be able to generate around 7KV or so at many hundreds of mA to low amps (!) with very high stability with only a single 24V 5A input.

I've used this trick with separate cold cathode inverters and it works well. Resistors MUST be correctly rated for the full operating voltage or Bad Things (tm) will happen.

YMMV, TANSTAAFL, ROFL, etc.

-A

Shaun

Mon Mar 24 2008, 05:52PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Wait a minute Conundrum, something seems wrong there. 5A @ 24V is 120VA, but 7kV and several hundreds of mA to low amps is around 3.5KVA to 10KVA.

The voltage must drop a lot once the tube ignites in order to maintain that conservation of energy thing...

Carbon_Rod

Mon Mar 24 2008, 10:01PM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

sorry, no website ;o)

Perhaps, OSRAM will send a sample of E20N81G2 to you for free...
Much easier to handle...

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