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    Make a led shut down immediately after power off

    Hello.i have a full wave rectifier followed by a capacitor and a led in series with a resistor.When i power off the circuit the led slowly turns off due to the capacitors charge.How to make it turn off immediately at the moment i remove the ac power? i dont mind using extra circuit.

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    Re: Make a led shut down immediately after power off

    Hi,

    omit the capacitor

    Klaus
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    Re: Make a led shut down immediately after power off

    Add a second rectifier (full or half wave) and a much smaller capacitor (or no capacitor) for driving the LED.



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    Re: Make a led shut down immediately after power off

    Do you want the capacitor to discharge too or just the LED? As an engineer who has to touch high voltage circuits I like LED's that are on until there is truly no power.

    Either move your LED onto its own source without any C or make an AC detection circuit that disables the LED.

    A capacitively coupled solution may be good in either case.



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    Re: Make a led shut down immediately after power off

    Or:
    and put a series blocking diode between the rectifier and the bulk capacitor. Wire your LED right after the bridge rectifier, but BEFORE the bulk capacitor.
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    Re: Make a led shut down immediately after power off

    and put a series blocking diode between the rectifier and the bulk capacitor. Wire your LED right after the bridge rectifier, but BEFORE the bulk capacitor.
    I think that should read... "but BEFORE the series blocking diode."

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  7. #7
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    Re: Make a led shut down immediately after power off

    You are absolutely correct Brian, but you still were able to get the gist of it.
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