Car Dome Light Off-Delay

[Tehop]

How this can do coupling for standard dome switch connect that can adjust delay time??

[kam]

when the door opens, C1 is charged to maximum. when the door is closed, the capacitor will start discharging through T4 slowly. The rate of discharge is controlled by the potentiometer R4. The transistor T1 will conduct as long as the capacitor's voltage is above 0. This transistor keeps the lamp grounded (like the door switches do)  as long as the capacitor is charged. Moreover, as the voltage of the capacitor falls, the base current of the T1 falls as well, and so does the collector current of the transistor. Therefore, the lamp dims slowly.

[Tehop]

Thank you for commenting on a lot of activity, connection works when you use the LED to come to disturb the bottom end of the light.
How could it get away with changing the interface ??

[kam]

i cannot underrated your question mate 

[Tehop]

I mean when use led light system, when start deay time and voltage beging down and light fade down. Problem is
use led light, it not come dark total completely - off, only can see little bottom light. This work completely only with normal bulb.

Question is, how this coupling can change that can avoid this problem do what, because use power resistor with led lamp haven't good idea and ergonomy in car roof??

[kam]

oh i see. well, with this circuit it is difficult to achieve what you want, because it is designed for high current incandescence lamps. I have not test it, but you can start by reducing R2 down to 470 Ohms

[Tehop]

Now i find result what work also for LED - light, little change coupling. And do it that understand more easy right.
If change this R1 value down this do only more fade time hard and fast.