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Button-Controlled LED (Arduino)

Light an LED while a push button is held down. Learn digital input with the built-in pull-up resistor.

Beginner15 min

What you need

Wiring

Arduino Uno
Push button
LED

Hover a pin or a wire to trace the connection.

Code

button_led.ino
// Turn an LED on while a push button is held.
// INPUT_PULLUP means the pin reads HIGH normally and LOW when pressed —
// no external resistor needed.

const int buttonPin = 2;
const int ledPin    = 13;

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  if (digitalRead(buttonPin) == LOW) {   // pressed
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(ledPin, LOW);
  }
}

Steps

  1. Wire the button: one leg to D2, the opposite-corner leg to GND.
  2. Wire the LED on D13 through a 220Ω resistor, cathode to GND.
  3. Upload the sketch.
  4. Hold the button — the LED lights while it's pressed.