Time delayed capacitor/resistor shut-off

Discussion in 'General Electronics Chat' started by ESPguitar, Sep 21, 2005.

  1. ESPguitar

    Thread Starter Member

    May 15, 2005

    I have to make a circuit:
    In a car, when we open the door the light inside the starts to lights, when we shut the door it takes som seconds before the light turns off..

    This delayed shut-down has to be 5 seconds, and i can't use timer chips ++, just traditional components like resistors and capacitors, wehen we open the door the light shall turn on immediately! I had some ideas but i can't draw it on my computer yet so i'll have to ask you guys for help..


  2. Gorgon

    AAC Fanatic!

    Aug 14, 2005
    Hi Robin,
    This should be solvable with a transistor and some discrete components. Normally the door switch is just shorting the wire from the light to chassis or 0v. +12v is supplied direct to the lamp. But it could be more sofisticated.

    You could try to use a big electrolytic capacitor and connect it across the door switch. This depends on the current drawn from the light and I think 5 seconds is a bit too long.

    What you need to do is to insert a transistor to turn on the light and the switch(es) to activate the transistor and a delayed turn off circuit.

    For the exact construction I need more info in the door switch and light.

    TOK ;)