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Thread: Solution required

  1. #1
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    Default Solution required

    I have a few AC led snowflakes that randomly will not dim to fully off .
    I seem to recall there was a solution for this but i cannot find a specific thread .

  2. #2
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    Default Re: Solution required

    Look up snubbers.
    Phil

  3. #3
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    Default Re: Solution required

    I was looking at snubbers and it seemed as they were referencing flicker reduction with the 47k resistor.

    Other snubbers I have read about seem to use a resistor and cap in parallel .
    Last edited by angus40; 08-28-2021 at 04:06 PM.

  4. #4
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    Default Re: Solution required

    "Snubbers" as we use them put enough of a load on the TRIAC to allow them to totally shut down. Some LED strings didn't present enough for the TRIAC to do so.

    Not sure what the capacitor was doing for them, but we never added them to our outputs. Just the resistors.
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  5. #5
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    Default Re: Solution required

    The capacitor+resistor combination was to reduce noise on the AC line (typically from other channels) that caused flickering. The capacitor would be counter-productive for ensuring that the triacs completely turn off. The other thing that might help is to make sure that the SSRs are completely dry and clean, as moisture and dirt on the board could provide a path for current to flow over the surface of the PCB, bypassing the triacs.
    Phil

  6. #6
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    Default Re: Solution required

    Thanks for the explanations .
    I am getting the same results with the single channel AC controller ,so I will now be adding
    the snubber to all of the snowflakes .

    I did not realize that some AC mini incans were acting like a snubber until I disconnected them.

  7. #7
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    Default Re: Solution required

    Thanks for the explanation. We use a power line filter on the way into the controller to take out the flickering caused by powerline noise/interference. Note that our main AC controllers are Renard SS16 or SS24 units. (Still going strong after 11 years!)
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  8. #8
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    Default Re: Solution required

    LED’s are diodes and diodes have a small amount of capacitance in the reverse direction. TRIAC’s turn off when the current passing through them reaches near zero.

    The problem is that the capacitance causes the current to lag a small amount behind the line voltage. The current is still high enough from the previous cycle as the voltage starts to rise from zero and for a short time, there’s power to turn on LED’s at the beginning of a cycle.

    The easy solution is to draw a little more current with a parallel resistor to counteract the battery effect of the capacitance.
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