Button Controlled LED

Press a button to turn on an LED.

Beginner
Input & Controls
5 parts

Opens in your browser with the parts, wiring and code already in place. Press Run to watch it work, then change anything you like.

How it works

A push button connects 5 volts to pin 2. While the button is pressed, pin 2 sees 5 volts and reads high; when it is not pressed, it reads low. The LED on pin 13 (through a resistor, to ground) is the output. On real hardware you would also add a resistor from pin 2 to ground, called a pull-down and usually 10 kΩ, so the pin reads a clean low when the button is open instead of floating.

loop() reads pin 2 with digitalRead() about ten times a second. If it reads HIGH the sketch lights the LED and prints “Button pressed - LED ON”; otherwise it switches the LED off and prints “Button released - LED OFF”. Click and hold the button in the editor while it runs to see the LED follow it.

Parts

Arduino Uno
Push Button
Resistor
LED
GND

Wiring

Arduino Uno 5V → Push Button A
Push Button B → Arduino Uno D2
Arduino Uno D13 → Resistor A
Resistor B → LED Anode (+)
LED Cathode (-) → GND

Arduino code

// Button Controlled LED
void setup() {
  pinMode(2, INPUT);
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int buttonState = digitalRead(2);
  if (buttonState == HIGH) {
    digitalWrite(13, HIGH);
    Serial.println("Button pressed - LED ON");
  } else {
    digitalWrite(13, LOW);
    Serial.println("Button released - LED OFF");
  }
  delay(100);
}

Try changing it

Flip the behaviour so the LED is on until you press the button: change buttonState == HIGH to buttonState == LOW.
Change delay(100) to delay(1000) and notice how sluggish it feels: the sketch only looks at the button once a second.

Open this circuit and run it

Next challenge

Interrupt Button CounterAn interrupt toggles the LED the instant you press the button, even while loop() is busy…