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Keep blowing transformers

Discussion in 'General Electronics Discussion' started by Danickstr, Aug 22, 2015.

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  1. Danickstr


    Aug 22, 2015
    I put a 120v to.12v AC transformer in a light switch box. I added a bridge rectifier to make it 12vdc. The rectifier gets hot but the load is only around 15 watts for an LED strip light. Not sure if I should add some other components to keep the transformers from going to 0 volts over time. They are rated for 75 watts - standard 15 dollar item for low voltage halogens.
  2. davenn

    davenn Moderator

    Sep 5, 2009
    hi there
    welcome to EP

    you have told us nothing about the ratings of the 120V - 12V transformer
    and what are the actual ratings of the LED strip ... voltage and current ?

  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    It sounds like you're not regulating the current to the LED strip and it is drawing enough current to overload the transformer to such an extent that it fails.

    12V AC will produce a peak DC of about 17V.

    I bet the LEDs are impressively bright.

    You might find some useful background information here.

    I recommend you look for a 120V LED driver appropriate for your LED strip.
  4. Tha fios agaibh

    Tha fios agaibh

    Aug 11, 2014
    I agree. Also, using the lightswitch box in this manner is an electrical code violation.
    A LED driver that's UL listed for the purpose is the way to go.
  5. HellasTechn


    Apr 14, 2013
    I agree with steve and i would also recommend to place a fuse in series with the transformer at the transformers amp rating to protect it from being damaged again.

    Theese led strips do have to be current regulated due to the heat they produce that changes their electrical characteristics.
  6. Colin Mitchell

    Colin Mitchell

    Aug 31, 2014
    Put a 10 ohm 10 watt resistor in series with the LED strip.
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