Power Adapter Question

Discussion in 'The Projects Forum' started by cpapaya, Feb 22, 2018.

  1. cpapaya

    Thread Starter New Member

    Feb 22, 2018
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    I purchase a 100 pack of laser diodes. Each one is 5V and 5mW.

    I soldered all of the negative leads together. Than I soldered all of the positive leads together. So I believe they are wired in parallel.

    What type of power supply can I connect to the braided leads to power these lasers? I tried a 5V 2A AC-to-DC adapter but it did not power them.

    Thank you.
     
  2. cpapaya

    Thread Starter New Member

    Feb 22, 2018
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    Here is the pack I got from ebay.

    And here are also some pictures of what I made. I made it so I can use it as a coaster and set my cup of vodka and sprite on it and the cup will glow red. And if there is a lemon in the cup it will be red too. G0011388[1].JPG GOPR1389[1].JPG
     
  3. wayneh

    Expert

    Sep 9, 2010
    16,024
    6,119
    Connecting them all in parallel was a bad idea. The ones with slightly lower Vf will hog all the current until they burn out, then on to the next.

    Each one needs its own current limiting supply. With so many, the only practical solution is a resistor for each one.

    If you can use higher voltage, you can put several LEDs in series with a single resistor, and then add many such series strings in parallel with each other.
     
  4. Sensacell

    Moderator

    Jun 19, 2012
    2,273
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    Without a data sheet for the part, it's guessing time.

    If perhaps they have an internal driver, you might get away with a beefy 5V supply.
    If no driver, then you must have an external current limiting mechanism on each one.
     
  5. Colin55

    Active Member

    Aug 27, 2015
    519
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    With a 5v supply you can put 2 in series and then a 47R resistor
     
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Are the laser diodes supposed to be emitting in the visible wavelength range or infra-red?
    Whatever, 500mW of laser radiation would be a serious health hazard!
     
  7. cpapaya

    Thread Starter New Member

    Feb 22, 2018
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    I was following the instructions on this video. It looms like he got it working by wirong them in parallel. Thd only dofference is he used aa batteries and im using an ac-to-dc adapter. I really dont want to go through the trou le of resoldering everything all over again. :(
     
  8. cpapaya

    Thread Starter New Member

    Feb 22, 2018
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    I attached a 5v 2a power adapter to it but they dont light up.
     
  9. cpapaya

    Thread Starter New Member

    Feb 22, 2018
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    They are supposed to be emitting red light. I removed the lenses from all of them so they arent lasers anymore, just red light.

    All joking aside i am trying to build what that guy built in the youtube video.
     
  10. DickCappels

    Moderator

    Aug 21, 2008
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    The "driver" is probably a resistor of between 50 and 100 ohms.

    Measure the current drawn by one of them then multiply that by 120 (for some margin) and buy a power supply that can provide that much current.

    If one in the 100 is shorted it will prevent all of them from working, so you might have to "unparallel" them and check them individually.
     
  11. cpapaya

    Thread Starter New Member

    Feb 22, 2018
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    Cant i just take a multimeter and test each diode individually for continuity?
     
  12. cpapaya

    Thread Starter New Member

    Feb 22, 2018
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    They are supposed to emit visible red light. They are basically red led diodes but i have removed the focusing lens from each of them. It is this focusing lens that cause the light to form a laser beam. The ibjective is to get the array to power in so i can place it on my head and maybe it will regrow the hair in my bald spot.
     
  13. Colin55

    Active Member

    Aug 27, 2015
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    You will burn a hole right through your head.
     
  14. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    You can't test them individually if they are wired in parallel. You could set your DMM to its diode test mode and check the array as a whole. That might tell you if there is a shorted diode in the array.
     
  15. cpapaya

    Thread Starter New Member

    Feb 22, 2018
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    If thats tru then why did the guy jn the video do it? He seems just fine.
     
  16. cpapaya

    Thread Starter New Member

    Feb 22, 2018
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    Ill try this. The guy in the video made it look so easy.
     
  17. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Don't believe evrything you see in videos :).
     
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