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LED pucks getting hot

Discussion in 'LEDs and Optoelectronics' started by Mark80, Sep 15, 2016.

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  1. Mark80

    Mark80

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    0
    Sep 15, 2016
    Hi,

    I recently purchased six 3W 12v LED undermount puck lights. I then purchased a 120vac to 12vdc 40W magnetic transformer/driver designed for LEDs.

    I connected all the LED pucks in parallel and they work, but after about 30 minutes they are almost too hot to touch. I fear they are being over driven and will eventually burn out.

    If I connect two puck in series, they run dimmer (not ideal), but don't ever seem to get hot. This leads me to think that individually they are getting too much current. I think the transformer voltage is stable - I get a reading that hovers around 13v. Is there something that I could add to fix this? I don't want to lose the brightness of the LEDs.

    thanks!
     
  2. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    Link to the "pucks" that you bought?

    Bob
     
  3. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    The link for the lights doesn't indicate normal current at 12 V. Running at 13 V they could draw excessive current the result of higher current and higher voltage means lots more power. They are dimmable? A dimmer might be your answer.
     
  4. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    You could also try placing one or two forward-biased diodes in series with the power pack output to drop the voltage presented to the puck lights.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Yeah, sounds like neither the LEDs or the power supply are current line limited.
     
  6. Mark80

    Mark80

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    Sep 15, 2016
    Could this be a AC ripple issue?
     
  7. BobK

    BobK

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    Jan 5, 2010
    Ripple should not be a problem, since the puck most likely just contains 3 LEDs in series plus a resistor.

    The problem is too much voltage.

    Bob
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Heh, I agree about the three LEDs in series, but there is no evidence of a resistor :)

    (which is not to say there is not one)
     
  9. BobK

    BobK

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    Jan 5, 2010
    If there is no resistor, then 12V is too high.

    Mark, can you measure the current drawn when you supply 13V to the puck?

    Bob
     
  10. Mark80

    Mark80

    15
    0
    Sep 15, 2016
    The LEDS have built-in resistors.

    I added a dc/dc buck and that seems to have solved the problem. The "LED transformer" was not putting out a constant 12V, so now it's more stable around 11ish V.
     
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