Arduino LDR Automatic Night Lamp

The question

An LDR (light sensor) is on A2 and an LED on pin 2. Turn the LED ON when the reading is below 400 (dark) and OFF otherwise.

The sketch

void setup() {
  pinMode(2, OUTPUT);
}

void loop() {
  int light = analogRead(A2);
  if (light < 400) {
    digitalWrite(2, HIGH);
  } else {
    digitalWrite(2, LOW);
  }
}

Wiring

LDR module: VCC → 5V, GND → GND, AO → A2. LED → 220Ω → pin 2.

How it works

1. 1analogRead() gives a lower number when it is darker (with the usual LDR module wiring).
2. 2If the reading is below the threshold, it is dark — turn the LED on.
3. 3Otherwise turn it off. The threshold is tuned by watching the readings.

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