dome light fade in

[chcknugget]

Is it possible to make my dome lights slowly fade on and off by putting a small capacitor on the power soirce for the domelight?
Has anyone tried this?

[BlazerLT]

No, and where did you find out that you could do this.

What purpose would it serve?

[chcknugget]

I just know from my experience in circuits that a capacitor takes a while to charge and discharge and will slowly allow current to pass through a lightbulb when in series with it, but it will also maintain charge after the voltage drops, allowing the light to slowly fade off.

[DJSteve]

It would work in theory, however I imagine it might take a pretty large (impractical) capacitor. You would also want the cap paralell, rather than in series. A capacitor functions by resisting a change in voltage, so you would want it across the +/- feeds so it holds the voltage when battery power is disconnected.

If you want to look into it further, I could probably help you determine what size capacitor would be needed to fade the lights over a given time. You would need to take measurements of the current going to the dome lights (pull fuse and put ammeter between terminals in the fuse block) and battery voltage. If you know current and voltage you can determine resistance by ohm's law. Normal RC circuit equations, or a circuit simulation program, can then determine the rate the voltage will fall. Or course that assumes the resistance of the bulbs remains constant as the voltage drops so it wouldn't be exact, but should give a good idea.

[chcknugget]

Ooops yeah, I meant parallel of course...

It might be cheesy to do this, but I just wanted to know if it might work. I would only do it to my top domelight, so it would probably be like .1 A or something.

How do you think mercedes and other brands do the dome light fade?

[04 blazer]

The dome light in my wifes '95 Cavalier fades out. Maybe if you can find a diagram for a Cavalier that will help you out. I looked in my Haynes manual, but it did not show a anything.

[rlith]

Yes, just wire a cap inline to the overhead light power... It won't fade on, but it will fade out.... Probably a 400 would do it, they're small but should roughly hold a 10 second charge before it fades. SO when you open the door it charges, when you close it it dissapates....