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Delay off delay circuit

Discussion in 'General Electronics Discussion' started by remzy, Sep 6, 2017.

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  1. remzy

    remzy

    47
    1
    Jun 12, 2015
    Hello everyone. I want to make a delay off circuit to use in my car's dome light because right now it turns off when I close the door and I want it to stay on for about 15 seconds after I close the door. I found a circuit which works but the problem is that it is activated by a positive voltage, and there is no way to activate it because my car's door switch switches a negative voltage, i think they've done it that way because they only need one wire to dome light instead of two if it was switching positive voltage. Is there a way to activate this circuit with a negative signal-voltage? Here is the circuit:
    Screenshot_2.jpg
     
  2. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    648
    May 8, 2012
    A 555 Timer will trigger on the negative going edge and provides enough drive current to drive a small relay coil.
    However, before you go through the work of brewing your own check out Ebay under "Delay Timers". The Chinese can sell you a complete timer with 'on board relay' for less than you could make it yourself.

    Chris
     
  3. 73's de Edd

    73's de Edd

    2,916
    1,233
    Aug 21, 2015
    Sir remzy . . . . .
    If your vehicle is using the typical dome light circuitry shown, which uses a grounding switch in each door . . .then . . .the second circuit using 9 common parts should give an all solid state solution.
    In final evaluating, if more delay time before dimming is needed increase the circled capacitors value.


    Le Schematique . . . . .


    AUTO DELAYED DOME LIGHT CKT.png

    73's de Edd

     
    Last edited: Sep 7, 2017
  4. remzy

    remzy

    47
    1
    Jun 12, 2015
    Thanks for the circuit. I will try it out. There might be issues because I've modified my dome light from incandescent bulb to LED's.
     
  5. 73's de Edd

    73's de Edd

    2,916
    1,233
    Aug 21, 2015
    Sir remzy . . . . .

    Should be no problem, if about the same or EXPECTEDLY pulling much less power consumption, the T2 "electronic switch" should then be able to loaf.

    73's de Edd
     
    remzy likes this.
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