Dome light dimmer (with delay)

Intro & disclaimer
For all you guys out there that want a fading dome light (aka courtesy light aka theatre lighting) without having to pay for one, you can build your own. I have attached the schematics and you can build it for a few bucks given that you don’t have any spare components lying around otherwise it can cost you absolutely nothing. Of course you can rip some parts from your TV, CD player, radio, etc., but I’m not responsible for the damage you cause this way

The way it works
I won’t bother you with technical details, but if someone is interested just let me know and I’ll explain in detail. For now just the basics. There are two stages: first one is delaying and the second one is fading. When you open the door the light turns on. You get inside and close the door, but the light stays on (delay stage) for an adjustable period of time (0-40 sec. for the values in the scheme, but you can easily modify that i.e. put a bigger capacitor) so you can see where to insert the key or do whatever you do when you get in the car, then fades away (fading stage) with an adjustable speed. If you connect the ACC wire (which is entirely optional) when you turn the key to ACC position the light turns off (actually fades) even if the delaying stage is not over (it cancels the delay stage).

Setup
The SR1 trimmer pot adjusts the delaying time (the period that the bulb is at full intensity) and you have a “witness” LED that is lit during the delaying stage; that way you can set it visually to whatever duration you like. When the first stage ends (marked by the LED not being lit anymore) enters the second stage – fading. The SR2 trimmer pot adjusts the fading time (or speed if you prefer)

The image above depicts how the dome light switch is usually connected (depending on the make and model of your car the connection may be different in which case you’ll have to figure it out).
The image below shows the schematic and the connections to the dome light switch.

Copyright 2005, kronos

7 thoughts on “Dome light dimmer (with delay)

  1. framistat

    Thanks for the circuit. I’d be interested in the technical details… Can this be breadboarded substituting an LED and resistor in place of the dome light?

    (Had to substitute a 2N4401 for the BC413C which is no longer available – at this point it doesn’t matter because the ACC wire is not connected.)

  2. Winston

    Hi, I have a question. I followed your circuit diagram and created the circuit.

    Everything works fine, however there is just one small problem.

    The lamp does not turn on when ACC power is on. Is there a way to modify the circuit such that if ACC power was on and door is opened, the dome light still comes on, and the moment door closes, dome starts dimming immediately.

    Thanks!

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