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Car, Automatic Light

This compact circuit automatically turns on the car lights when ambient light levels drop — for example, when entering a tunnel or dark area.

It operates from a 9V supply, so when connecting it directly to a 12V car battery, a 12V-to-9V DC-DC converter is required.

The light sensitivity is adjustable using VR1, allowing the user to set the precise brightness threshold at which the lights activate. The circuit uses a Light Dependent Resistor (LDR) to detect surrounding light intensity, and BC547 and BC337 transistors to amplify and switch the signal that drives the relay controlling the car lights.

This system offers:

  • Automatic response to lighting conditions
  • Adjustable sensitivity
  • Simple and reliable operation

Ideal for vehicle automation projects, energy saving, and driver convenience.

Electrical Diagram

Automatic car light schematic

PCB and parts layout

Automatic lights for car pcb