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    TRIAC wont conduct, some advice needed

    Hi guys,
    I am having problem with triac conducting.
    In attached schematics triac should control current through R1 by turning potentiometer. I found somewhere on the net schematics and i thought it will work, I dont have to much experience with TRIACs so i would like to hear youw suggestions.
    And I am well aware about position of pins regarded to gate terminal, first i thought that maybe i have switched pins but that is probably not the case. I hope it is probably something that i have overlooked

    Click image for larger version. 

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  2. #2
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    Re: TRIAC wont conduct, some advice needed

    If anything I would expect it conduct most of the time. R2/C1 are a phase shift network to delay the trigger voltage reaching threshold and hence reduce the time current flows but it should conduct more time than less with those values.

    Brian.
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  3. #3
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    Re: TRIAC wont conduct, some advice needed

    If the triac is connected as the schematic symbol tells (G next to A1), A2 to ground, the trigger current must be provided by the capacitor, which probably doesn't work at 24 V.


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    Re: TRIAC wont conduct, some advice needed

    Quote Originally Posted by FvM View Post
    If the triac is connected as the schematic symbol tells (G next to A1), A2 to ground, the trigger current must be provided by the capacitor, which probably doesn't work at 24 V.
    what do you mean by capacitor doesn't work at 24V?
    I thought that maybe it's value is to low so the charge is not sufficient to provide enough current to trigger TRIAC.
    Do you perhaps have some suggestion?



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    Re: TRIAC wont conduct, some advice needed

    Hi,

    220nF @50Hz gives 14.5kOhms.
    At 24V RMS sine this gives 1.6mA RMS. Not enough to generate the specified 5mA trigger current.

    Klaus
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  6. #6
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    Re: TRIAC wont conduct, some advice needed

    I still suspect, that the present triac connection isn't intended, usual scheme would connect A1 to ground.



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