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Thread: High Power Coherent Laser Diodes on Ebay

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    Default High Power Coherent Laser Diodes on Ebay

    Hello all,
    I am new here. I have been an on and off lurker for some time now. I recently got one of these high power laser diodes on ebay:http://cgi.ebay.com/ws/eBayISAPI.dll...m=130303050585

    Now, the auction says 35watts. The seller says 35watts. But these look ALOT like the youtube ones that are more like 60Watt lasers AND the seller claims they threshold at 17amps. I spoke to a few others that bought the lasers and one agrees that they are indeed the 50-60watt laser diodes that made their way onto youtube. (Cutting soup cans and unleashing general hell on most materials).

    A few others claimed that they cant handle more than 17amps and one fellow claimed his died when he drove it to 25amps. My bet is that these are the super high power lasers on youtube, but that the few that complained simply dont know how to use them. Water cooling is critical for even a second. A good driver is also important, but seems less important than cooling.

    So I would like to get some thoughts on these lasers. Crap? Worthwhile gamble? $150 shipped for free seems like an excelent deal for these things!

    Here is how I plan to run it:
    Cooling: I have one of those prowater Thermaltake CPU water cooling kits. I will use the pump and radiator to cool the laser. If these CPU coolers are not enough, I could add the included waterblock into the system and put it on a 12volt 6A peltier I ripped out of a coherent FAP module (for a 40watt diode). This ought cool the water, no? Do these things require special liquids, or could I use deionized water from the supermarket?

    POWER: I built a constant current driver using three op-amps to control three 75amp mosfets. Current control is via a precision potentiometer and a precision voltage reference. Power is from a 5 volt 40amp vicor flatpac. (Voltage trimmed down to 2.8volts). I added a pi filter on the output to cut output ripple.
    I will need to add another 5 volt 40amp flatpac in parallel to run this to its max, but for now will stick with 40amps.

    How does all this sound?
    Thanks much!
    Matt

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    It is hard to say what diode is actually in those monsters, but it is very possible that there is a 100w QCW diode in there, and the threshold current of 17A is definitely a good sign of a 60w or 100w QCW bar in there.

    As to cooling the beast, ordinary water is probably fine as long as you are not trying to pump YAG with it, you would see a small amount of power gain by running the diode below room temp, (to get an idea of what you are misisng out on, run it off tap water which will be at about 60f) and compare the power to running closed loop. I would expect somewhere 10%-30% loss depending on how good of a radiator you have. You could try with the tecs, but I don't think you will gain much--but its worth a shot. You would be a lot better off putting the tec directly between the diode and the coldplate (using a standard ccp mounted bar and your own optics would be your best bet at that point), because you don't have to deal with the temperature drop across 2 waterblocks and their associated thermal interfaces.

    You can use any water you want with these lasers, they aren't like yag lasers with HV electrodes submerged in the water, the case is essentially a waterblock with a ccp mount diode mounted internally. Even tap water would work fine with it

    Your homebrew power supply should work great with this laser, for a good source of high power power supplies look at power supplies for old computers. I have a supply out of an old sun ultra60 that has a 60A 3.3v bus and a 30A 2-5v adjustable bus!

    Good luck with it, high power lasers are dangerously addicting...

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    I have been messing with these things for a while now. Check out my videos.... http://www.youtube.com/watch?v=6Kh7LmzaTeM

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    What are those diodes normally used for then?

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    Quote Originally Posted by madgadget View Post
    What are those diodes normally used for then?
    They came out of plate setters of a newspaper press.

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    I wonder why the seller sells them as 35watt diodes when they clearly can be good for so much more?

    Now I need to find a way to convert from 3/8in ID tubing down to whatever these lasers water cooling nozzles are...Any ideas? What size tubing do you use? I want to use a CPU liquid cooling kit I got, but its tubing is 3/8in ID (much bigger than this laser's ).

    Matt

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    Quote Originally Posted by mattrg02 View Post
    I wonder why the seller sells them as 35watt diodes when they clearly can be good for so much more?

    Now I need to find a way to convert from 3/8in ID tubing down to whatever these lasers water cooling nozzles are...Any ideas? What size tubing do you use? I want to use a CPU liquid cooling kit I got, but its tubing is 3/8in ID (much bigger than this laser's ).

    Matt
    Because they are chosen to be ran greatly underpowered for lifetime reasons.

    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

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    Quote Originally Posted by mattrg02 View Post
    I wonder why the seller sells them as 35watt diodes when they clearly can be good for so much more?

    Now I need to find a way to convert from 3/8in ID tubing down to whatever these lasers water cooling nozzles are...Any ideas? What size tubing do you use? I want to use a CPU liquid cooling kit I got, but its tubing is 3/8in ID (much bigger than this laser's ).

    Matt

    The barbs on the laser head are 1/4" and you can pick up a 3/8 - 1/4" reducer at any hardware store.... However, this laser head needs more stability than a computer cooling kit is going to provide. What you could do is dump the radiator for a couple more CPU water blocks and run TEC's sandwiched between them with a big heatsink. Ofcourse you'd need a current regulating PS for the TEC's as well to get it to stabilize at operating temp.

    What you can also do is pickup one of the coolers I have for cheap and fix it. I have the quick disconnect nipples here I can provide you with. They are 1/4".

    See thread...

    http://www.photonlexicon.com/forums/...ight=thermotek

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    Hmmmm...Well I dont need to cool it for any yag pumping, just keep it from burning itself up for a few minutes...I wonder If I ought to use the pump to pump ice water through the laser? I dont need a permanent setup, this is just for fun.

    I checked home depot and lowes and neither had the 3/8in to 1/4in reducer. I hate those stores. I may look online, unless I could buy some off someone here? (Paypal).

    I may try the thing as is, with the radiator, and then try replacing the radiator with a waterblock/peltier combo, and then if that doesnt work I will just try ice water.

    I cant power this more than 40A right now anyways...I need to parallel another 40A flatpac in for 80A total, as well as adjust the voltage reference on the driver. (Its capped for 50A max current).

    Thanks for the tips guys! I powered it up at 30A for 1.5second intervals while watching the thermistor value. The thing deffinately needs water cooling! (Didnt let it heat up though). Got to see that the laser does indeed work. (Burned a line through some carbboard).
    Matt

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