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Thread: Understanding how to adjust driver pots

  1. #1
    Join Date
    Nov 2011
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    Frederick, Maryland USA
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    114

    Default Understanding how to adjust diode driver pots

    I have a fairly crappy 1W 445 which is grossly under powered (385mW). At first I cranked up the pots and was able to get it to just under 500mW. Then....i messed with it further and now I have a blanking issue where a long tail always appears. Obviously I don't know what I'm doing. On the driver board there are two pots, both of which I cranked up/then down..all different combinations. Stop laughing...can someone explain why I have this blanking issue now and if I shouldn't have messed with both of them.

    I was also told that the driver board can be upgraded to get the full 1W. How do I find out what I need to get to match the diode? It's Chinese and has zero markings. Will post pics if needed.

    Thanks all

    F7
    Last edited by Foxtrot7; 02-14-2012 at 07:25. Reason: added "diode" to title

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  2. #2
    Join Date
    Dec 2008
    Location
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    Default

    You haven't given enough information...

    Which 1Watt Laser are you referring to (Links)....???
    Which LD Driver...(pics)...???


    Jerry
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  3. #3
    Join Date
    Nov 2011
    Location
    Frederick, Maryland USA
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    Default

    Thanks for the reply Jerry. I'll post pics here in a bit. It came in a POS I ordered from PF lasers when I first got the bug. The projector was sold as a 1W 445. I was told that it's probably a 1W diode (again no markings) that could be modified with a different driver board.

    Pics to follow

    tks!

    KEEP it COHERENT!
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  4. #4
    Join Date
    May 2007
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    1 hr from everything in SoCal
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    Default

    If the diode driver has two pots, one is most likely the current adjust, and the other is probably the blanking gain. Do you know if this driver's blanking is TTL (full on/off) or analog (brightness is variable)? If there are no markings, it would be hard to determine which pot is doing what without a meter. If you have a meter that can measure current, then you are good to go. The bad thing about playing with the pots, if you don't know what they do, is that you might over-drive the diode. 445's are pretty tough, but you can still turn them into an LED if you over-drive them too much. My advice is to find a meter that measures current... they rest is easy and anyone here could walk you through it.
    If you're the smartest person in the room, then you're in the wrong room.

  5. #5
    Join Date
    Feb 2010
    Location
    Melbourne, Australia
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    Default

    If you are willing to sacrifice your diode (You may need to because I can't guarantee you have 1W+ diode)...

    Use the legal, correct, safety goggles for the correct wavelength diode whilst performing this process and never project the diode into an unsafe area, peoples' or animals' eyes etc. The diode should be pointed towards a dull black metallic fireproof surface, such as a dull black anodized heatsink. Or block of metal painted in matt high temperature black.

    1. Under ElectroStatic Discharge preventative conditions...
    2. Remove the driver wires to the diode. If the diode is not saved by a permanently connected Lasorb, try to keep the two diode contacts bridged (a tight small PC motherboard jumper can do the trick).
    3. Connect your amperage meter to the driver's output you've just disconnected from the diode.
    4. Bridge the modulation input cables (effectively this endures there's no difference in potential voltage between the input poles i.e. 0v modulation input).
    5. Turn on DC power to the driver.
    6. Reduce the output current to around 200mA using whichever of the 2 pots has an effect on the meter. You may need to turn 1 up to tun the other one down.
    7. You have just set the "bias". The pot that controls the 0v mod signal is the "bias".
    8. Turn off the DC power.
    9. Apply a clean regulated 5v to the mod input.
    10. Turn on the DC power.
    11. Adjust the other pot (leaving the bias set) until you reach 1,000 mA on the meter.
    12. You have just set the "gain".
    13. Disconnect the 5v mod signal.
    14. The meter should return to around 200mA.
    15. Turn off the DC power.
    16. The meter should drop to 0mA.
    17. Bridge the output wires.
    18. Reconnect the output to your diode.
    19. Turn on DC power.
    20. Optional: adjust bias up or down to set the diode to just below threshold (when it suddenly gets bright from a dull beam).
    21. Apply 5v mod signal.
    22. Measure the output beam. Depending on optics quality etc you should get between 700 and 1,000 mWs.
    23. Increase the gain to add output mWatts up to 1,000. Check to make sure neither the laser driver or the diode block, mount etc become to hot to touch. This heat will cause the diode to drop in power and could cause permanent damage to the driver and/or the diode, so be slow and steady.

    If you can't reach 1A without getting things hot or running out of Amps on the DC power supply, then you're pushing the electronics or diode too hard without cooling, bigger supplies etc.

    These diodes are normally quite rugged, so should take some abuse. If you're not careful, you may pay up to $50 plus shipping to replace 1 blue diode.

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