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Thread: DTR's Laser Shop: Diodes-Drivers-Lenses-LEDs & More

  1. #341
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    I was getting similar results, you certainly can't really over drive them with just a heatsink, maybe cooling to sub 18c might change that quite a bit like it does on most diode.

  2. #342
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    Yea my supplier said if you TEC cool them you may get some gains. I will be sending this exact unit I tested over to Lazeerer to confirm the testing on this one and try some TEC cooling on it.

  3. #343
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    Osram PL520 50mW 520nm Laser Diode

    Update as my lbII lpm was reading low.









    Ok so I got my PL520's in stock today and got some quick testing done on these tonight. Now I was really suprised how bright they really are and am very pleased with these diodes. They are the begining of a new era here for sure. I want to start off by saying these run extremely stable from what I have seen so far and they appear to be pretty damn tough as I have doubled the datasheet recommended current and have not seen any degradation on the diode. They can double the datasheet output or more but it is yet to be determined if it is good to run them that hard yet.


    Anyway here we go. They seem to have a lasing threashold of 70mA and there you will see about 15mW. This test was done with a G-2 lens.









    Next on to 100mA and it gets about 28mW.








    Next to 150mA and it jumped to 55mW. 27mW gain for 50mA.








    Next to 200mA max recommended current via the datasheet and we are seeing just under 80mW. 30mW gain for 50mA. This really may be the sweet spot.








    Now to 250mA and a jump to 96mW. Only a 16mW gain for 50mA.







    Next to 300mA and 107mW. So we are falling off the efficiency curve at this point. 11mW gain for 50mA.








    Next to 350mA and 116mW. 9mW gain for 50mA.







    And just for good measure on to 400mA and 118mW. 2mW gain for 50mA.










    So there we have it. With an acrylic lens you are probably looking at a 15-20mW decrease so looks pretty solid 80mW with a G-2 and probably 50mW with an Acrylic. There are still wavelength and controlled temperature experiments that can be done but I think that about sums up the output capabilities.


    Now on to divergence and different lens tests.
    Last edited by DTR; 05-03-2014 at 12:32.

  4. #344
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    Just stuck the heatsink in the freezer for 20 minutes and then put the module back in and took a measurement. 129mW @ 400mA. Also noted the forward voltage had increased by almost half a volt.

    Last edited by DTR; 05-03-2014 at 12:31.

  5. #345
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    at ~100mW, these things just became very practical for a teensy projector. two of these through a pbs cube would be very nice, and not that much more expensive than a decent quality 532 of comparable power.

    Quote Originally Posted by DTR View Post
    Just stuck the heatsink in the freezer for 20 minutes and then put the module back in and took a measurement. 129mW @ 400mA. Also noted the forward voltage had increased by almost half a volt.

    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  6. #346
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    Here is a quick graph to help visualize the numbers.
    Click image for larger version. 

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    These diodes are so small and have such a small surface area for heat sinking that they are not going to deal with high power levels well.
    In the graph you can see the knee right at 200ma so I wouldn't run these long term above 250ma. Any higher and you are fighting getting heat out of it.
    When you cooled it you only got 11 more mw out of it. A more interesting cooled test would be at 200 mw.



    Edit: some more thoughts.


    Chad
    Last edited by chad; 04-14-2013 at 10:47.


    When the going gets weird, the weird turn pro.


  7. #347
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    DTR you are sick!!!! Does your wife know what you stick in the freezer ?

    Nice testing there but what approx temp was it.

    If you end up killing one; could you de-can it and count the bond wires, this makes loads of difference if there are more than two.

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    I wish I knew the exact temperature. A temp gun is in my list of equipment to buy just have not got to it yet.

    The members over @ LPF pulled together to do a kill fund for two diodes. It may not be necessary to kill both after the data that has been posted but decanning one will probably be done to get a look inside. They will also be doing some cooling tests to get some better data than my freezer test.

  9. #349
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    Oh i thought of something else You might want to give the diode an extra volt ao 8 instead of 7 when trying to over drive it.

    chad


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  10. #350
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    Quote Originally Posted by chad View Post
    Oh i thought of something else You might want to give the diode an extra volt ao 8 instead of 7 when trying to over drive it.

    chad

    Little confused on what you are asking. I am using like 8.5V overhead or to say what it reads with no load on the bench supply but in the constant current mode I am driving it in the most it has pulled is the 7.4V @ 400mA cooled. You would have to turn the current up to get it to draw more voltage.

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