Interior Light Switch For Cars Schematic Circuit Diagram

Enhancing Car Interior Lighting

Modern cars often come equipped with automatic interior lighting that illuminates when any of the doors or the hatchback is opened. However, a potential issue arises if a door isn’t properly closed and the car is left unattended in the garage for a few days, leading to a drained battery. Fortunately, there’s a solution to this problem.

Introducing the Circuit Design

In this proposed circuit, the control of the interior lights is transferred from the door switches to the regular light switch. The circuit is built around a 555 timer (7555 or 555C) and functions as a monostable, activating the lights for four minutes once it’s turned on. The duration of this illumination period can be adjusted by modifying the values of R2 and C2. Additionally, the network R1-C1 ensures that the IC is triggered promptly upon the application of voltage.

The output of IC1 controls relay Re1 via T1. The only requirement of the relay is that it should be actuated by a voltage of 12 V and a current of less than 200 mA. As soon as the timer switches the lights off, the current drain drops to 6 mA if a 555 is used and to 0.5 mA if a 555C is used.

Before the circuit is built into the car, check how the door switches are connected. If they are in the +ve battery line, use variant A; if in the -ve (earth) line, use variant B.

Finally, connect the circuit to the junction of the wires from the door switches; otherwise, it will react to only one door.
* These days, even in the garage, it is best for security’s sake to properly shut and lock all doors and, if fitted, set the alarm.
* In quite a few modern cars, the circuit described (or one like it) is a standard fitting.