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Led fade control help.

Discussion in 'LEDs and Optoelectronics' started by Mig192, Oct 7, 2016.

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  1. Mig192


    Oct 7, 2016
    Is it possible to make an led slowly fade in when power is applied but then cut out immediately when power is cut? How could the capacitors discharge be channeled elsewhere in the circuit?
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Welcome to EP.

    Even though it seems not to fir your description, the circuit described here should be just right for you.
    Replace switch S1 by a direct connection to 12 V.
    The LED will fade in upon turning on the 12 V.
    The LED will instantaneously turn off upon turning off the 12 V.

    You may need to adapt component values for other supply voltages or an other number of LEDs.

    You may speed up discharge of cpacitor C1 by adding a diode in paralle, anode to 0 V, cathode to the capacitor's "+". This will arm the circuit for the next power-on sequence much faster.
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