Help Needed For Power Supply Project

Discussion in 'The Projects Forum' started by msdmsd, Nov 21, 2008.

  1. msdmsd

    Thread Starter New Member

    Nov 21, 2008
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    Let me start by saying that my technical knowledge of electronics and electronics terminology is limited.

    With that said I am in need of a circuit design or link to kits, plans or fully assembled power supply capable of variable voltage and amperage.

    I have salvaged three laser diodes form a combo hd dvd/blu ray player and am trying to make a laser pointer using the 405nm blu ray diode. I have very little idea of the power requiremnts for the diode except the voltage required is somewhere between 3.3 and 5.5 volts and an operating current between 25mA and 50mA. This is why I need variable voltage and amperage so I can start low and ramp them up as needed without destroying the diode.

    Any ideas or suggestions would be greatly appreciated.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    Do you have a meter?

    Here is a link into out Ebook that explains the care and feeding of LED's.
     
  3. msdmsd

    Thread Starter New Member

    Nov 21, 2008
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    Yes I have a meter...I did not see the link.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Lasers are particularly unforgiving when subjected to excess current. They'll die in a heartbeat.
     
  5. hgmjr

    Moderator

    Jan 28, 2005
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    I think this is the link that beenthere intended to post in his reply.

    hgmjr
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    Thank you - the dangers of posting after a long day.
     
  7. msdmsd

    Thread Starter New Member

    Nov 21, 2008
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    Exactly why I need some sort of adjustable current limiting...I'd hate to kill that blue laser diode.
     
  8. msdmsd

    Thread Starter New Member

    Nov 21, 2008
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    Thanks...it looks like a good start
     
  9. msdmsd

    Thread Starter New Member

    Nov 21, 2008
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    So i've read through that chapter in the ebook and it seems that a good start would be a transformer from one of the various wall warts I have laying around and a potentiometer to limit the current. Then using my meter I can measure the current at the point the diode starts lasing then up it by about 10mA?

    I guess the big question is the voltage drop of the laser diode...any thoughts on this? I have done some research and found 4.5 volts works for a blu ray laser diode from the ps3 but I'm not sure about the one I have salvaged.
     
  10. Wendy

    Moderator

    Mar 24, 2008
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    Use a constant current source, that is the key. Something low value. This link might apply for your needs.
     
  11. msdmsd

    Thread Starter New Member

    Nov 21, 2008
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    0
    Bill, thanks for your help...I think I am getting the grasp of this but I have a few more questions...I was looking at the LM317L and it looks like a circuit designed around this might be what I'm looking for but I'm confused on a couple of things.

    What is an appropriate power source? Could I use a wall wart transformer?
    I found the spec sheet and found a schematic for a adjustable voltage regulator and for an adjustable current limiter but how would I get both to work together?

    I'm a bit of a noob when it comes to this so thanks for all the help. This is turning out to be a great learning experience.

    Edit: I've been doing a lot of research on my own but I have another question that may or may not be stupid...would knowing the resistance of the laser diode help? Is that possible to get just using my meter?
     
    Last edited: Nov 23, 2008
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