Using this electronic circuit interior light on a room remain lit for approximately five seconds after the door was closed.
This circuit can be used for both cars and for other rooms.
When the door opens, the door switch (S1) is closed. The S1 and D2 closes and a current will flow through the inner bulb, L1. Meanwhile, C1 will be charged very fast capacitor through R1, D1 and S1.
When the door closes, S1 opens.
At the same time, T1 is brought conduction down the negative terminal of C1. After a short period, depending on the value of C1 and the base current of T1, T1's base voltage reaches the level at which the transistor stop conduction, so L1 is off.