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JEJunior Engineer LabPico W + micro:bit course
08 35 minutes

Automatic nightlight

A light sensor, two thresholds, and a lamp that will not flicker

Automatic nightlight project
Illustration of the finished idea. Build from the diagram and connection table, not the photo.

Mission goal: Replace the knob with a light-dependent resistor, calibrate your own thresholds, and build a lamp that switches on in the dark using hysteresis.

Section 1

Understand

New ideas

  • An LDR as half of a voltage divider
  • Calibrating with real measured readings
  • Hysteresis: two thresholds instead of one
  • Remembering the previous state
  • 1A light sensor plus a 10 kΩ resistor makes a light-to-voltage divider.
  • 2Two thresholds (LOW and HIGH) stop flicker at dusk.
  • 3Between them, the lamp keeps whatever state it was in.

Safety first

  • Unplug before removing the potentiometer and fitting the LDR.
  • Use the bare two-leg LDR from the kit, not a sensor module with extra pins.
  • Keep 3.3 V from physical pin 36. Do not use 5 V anywhere near a GPIO pin.