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Automatic Street Light with LDR

Concept

A light-dependent resistor changes resistance with ambient illumination. A controller can compare a sensor reading against a threshold and switch a low-voltage LED circuit.

Materials

LDR, fixed resistor, LED, appropriate current-limiting resistor, jumper wires, breadboard and a microcontroller.

Steps

  1. Build a voltage divider using the LDR and fixed resistor.
  2. Connect the divider midpoint to an analog-capable input.
  3. Test the analog values in bright and shaded environments.
  4. Set a switching threshold and drive a low-voltage LED through an appropriate resistor.

Use an isolated low-voltage demonstration only; do not wire mains street lighting.