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  1. #1
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    Jun 2010
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    Switching 24VDC LEDs with FEC outputs?

    Is there a trick to switching 24VDC on the binary & configurable outputs of an FEC? I have an led stack light that I'm trying to switch on and off and they switch on but not off I'm assuming this is because they are Triacs? I hope there is a way to do it with the controller, I don't really have any room to add relays.

  2. #2
    Join Date
    May 2012
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    Quote Originally Posted by nasaguyjoe View Post
    Is there a trick to switching 24VDC on the binary & configurable outputs of an FEC? I have an led stack light that I'm trying to switch on and off and they switch on but not off I'm assuming this is because they are Triacs? I hope there is a way to do it with the controller, I don't really have any room to add relays.
    There's no trick. Triacs simply won't RELIABLY switch DC voltages. It might work occasionally but there's no way it will work reliably. Perhaps you could switch 24 VAC and install a diode at the LED. It will be half wave but it will still light the LED.

  3. #3
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    They will reliably turn on, but they latch on until the current drops below their latching threshold. So on DC, good chance your going to see exactly what you are. It turns on and never off. With AC they will open every zero cross, unless triggered.
    Propagating the formula. http://www.noagendashow.com/

  4. Likes JCIman liked this post
  5. #4
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    Damnit.. Relays it is.. Thanks for the input.

  6. #5
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    Feb 2008
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    I would recommend the following to try:

    Set the FEC output jumper to switch the 24 VAC from the internal power source. Add a diode (IN4004) in series with the output to the LED.

  7. #6
    Join Date
    Apr 2014
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    The IOM's that have UO's (universal outputs) use FET's instead of TRIACS so they will switch 24 VDC. An IOM 3711 would have 4 relay outputs and 4 UO's so you could switch 8 24VDC loads with one.
    The suggestion to use a diod in series would work, but the LED will only see half the waveform. A full wave rectifier would be better.
    The best option is to probably change out the lamps to 24VAC.
    There are some nice 6mm thick, DIN rail, single pole relays available, that would be easy to implement.

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