Time delayed capacitor/resistor shut-off

Thread Starter

ESPguitar

Joined May 15, 2005
16
Hi!

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..


Thanks!

Robin
 

Gorgon

Joined Aug 14, 2005
113
Originally posted by ESPguitar@Sep 21 2005, 11:19 PM
Hi!

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..
Thanks!

Robin
[post=10511]Quoted post[/post]​
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 ;)
 
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