Halogen/ LED Trafo problem

Discussion in 'General Electronics Chat' started by boblalux, Dec 21, 2017.

  1. boblalux

    Thread Starter New Member

    Oct 16, 2015
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    1
    Trafo.JPG

    Just moved house and have a problem with exchanging all 12V 35W halogen bulbs, with 12V 5W LED bulbs.
    The latter work well for about 5 minutes, then start to (very weakly) flutter. After another 5-10 minurtes, some of the bulbs turn off. When I switch off, and then on again, the bulbs light up - again for another 5-10 minutes, and then the problem repeats itself. I note on the transformers concerned (see attachment), the phrase 'for 20-105 watts'. This is achieved with 2 halogens (70W total), but not for 2 LED bulbs (10W total). Is this the problem? Why should too LOW wattage give problems with the trafo?
     
  2. ian field

    AAC Fanatic!

    Oct 27, 2012
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    I'm kinda guessing your LED kit wants DC.
     
  3. boblalux

    Thread Starter New Member

    Oct 16, 2015
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    Thanks, but no, it requires AC.
     
  4. crutschow

    Expert

    Mar 14, 2008
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    It may be a solid-state inverter that requires a minimum 20W load for proper operation.
     
  5. ian field

    AAC Fanatic!

    Oct 27, 2012
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    The one I ripped was just a 2 transistor astable driving a CT primary - it would most likely keep going with no load.

    A dimmable PFC type would be more complex.
     
  6. crutschow

    Expert

    Mar 14, 2008
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    Well, there must be some reason it has a minimum power rating of 20W.
     
  7. DickCappels

    Moderator

    Aug 21, 2008
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    And what you describe may be overheating, cooling down, then overheating again,
     
  8. ElectricSpidey

    Member

    Dec 2, 2017
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    Simple way to find out...hook another load to the transformer...

    if it works then it needs a minimum load, if it shuts down even faster then it is overheating.
     
    whitehaired novice likes this.
  9. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    There are some protections in the transformer that will kick in:

    SNT 105SR_protections.png

    This is from an other brand with the same specs.

    Bertus
     
    boblalux likes this.
  10. boblalux

    Thread Starter New Member

    Oct 16, 2015
    17
    1
    Many thanks! Bob
     
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