car interior light timer

can anyone help with a circuit that will make my car interior light stay on for a while after i close the door?

i have a basic knowledge of components, and can solder. . .

any help will be much appreciated.

Well, to do that you might have to strip away some parts or you could just add a normal switch on your dashboard to control the light.

I really dont know how to add a delay to an analog circuit.

Most all cars I have seen, have the door switches in parallel to each other, however yours may be different, so you'll need to check. If they are all in parallel to each other, then you only need fit one of these across any one switch, obviously if they are not, then you would need one across each door switch you wish to control the delay from...
Just a side note, some cars do not rely on the screw mount on the switch to provide the body earth, so there may well be two wires going to the switch. The easy way to find out which one is which, is to remove the switch from it's location, push it to simulate that the door is closed, and measure the voltage on the two wires, the one with a voltage is the light end, the other is the body earth.

I have attached a schematic here for you to follow, the capacitor is rated 25V, the transistors are not particulary important, pretty much any old junk will do, but you may need to fit a small heatsink to the darlington just to keep things sweet...to change your delay time, increase or decrease the value of the R4 and/or C1. I Hope this help you out

Wow, thanks tuned wolf, I was looking for an analog way to do this. Have to brush up my elec

The most common method is to use a 555 timer - there have been hundreds of circuits for doing this over many decades.

Modern versions tend to use a PIC, which allows far more accurate timing, and extra facilities - usually fading the interior light off, rather than switching it.

the circuit I just gave him will fade the lamp off...

Thanks. I'll try building this as soon as i get hold of the darlington pair.
You've been most helpful...

just a thought, could i make a darlington pair with a couple of npn transistors? would it work? i have a couple of bd243c's lying around.

Nothing to stop you really, if you can find a good match for the transistors, but the overall gain might not be as high as a proper darlington, so it may not put the lamp fully on, and will result in more heat dissipation. I have only ever used a darlington in that circuit, so I haven't had the need to try.

I would prefer the 555 option, because it's so much easier to calculate the delay and you can use a MOSFET driver transistor which has virtually no voltage drop.

well...instead of just saying that post a small schematic so he can do something with the idea...