Controlling LED lamps with Triac.

Discussion in 'Power Electronics' started by shein, Oct 17, 2016.

  1. shein

    Thread Starter New Member

    Sep 11, 2012
    3
    0
    Hi All,

    I'm building a little project that controls my lamps. I have 220V LED lamps installed everywhere.
    In order to fit everything into a wall switch I had to use as compact components as I can.
    So, I decided to use a Triac as a load switch. To isolate mains I use optocoupler.
    I used a circuit from the datasheet:
    [​IMG]
    Triac: BT134-600E (from aliexpress)
    Optocoupler: MOC3021 (from aliexpress)

    Problem:
    When I start using the whole device at first everything works as expected. LED lamps are controlled fine. After some time (from minutes to hours) the triacs start to fail. One triac failed completely. Others just start leek some current in off state (so LED lamps start to flicker)

    Question:
    I'm I doing something wrong?
    Can 220V LED lamps be the cause of triac destruction? (the triacs stay cold).

    Thanks!
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    Ideally you need a zero crossing opto like a Moc3032, and put the load in the Neutral side,

    circ57.gif
     
  3. shein

    Thread Starter New Member

    Sep 11, 2012
    3
    0
    Thanks @Dodgydave for the reply!

    Yes, my load is in the Neutral side.

    As far as I understand the zero-crossing prevents big inrush currents when load is turned on at peaks of sinusoidal AC signal.
    Can It be that big to destroy an output triac?

    I also have a question about the snubbing circuit that is recommended to use to drive an inductive load with a Triac.
    I'm not sure if my load is inductive enough to require such a circuit? Suppose I have some kind of SMPS inside my LEDS.
    Do I need a snubbing circuit to drive a switch mode power supply?
    circuit.PNG

    Thanks!
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    Yes, a switch mode psu is an inductive chopper psu, taking chunks from the mains at high frequency,.
     
  5. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    632
    Some LED lamps are "dimmable" and others are not. It might be that your lamps are not dimmable and is the cause of failure.
     
  6. shein

    Thread Starter New Member

    Sep 11, 2012
    3
    0
    Yes my LED lamps are not "dimmable" and I don't want to dim them, I just want to switch them on and off.
     
  7. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,887
    375
    I think a snubber circuit is indicated.
     
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