Tutorial 2 - Button Controlled LED

Control an LED using a push button. This tutorial introduces digital input using digitalRead() and conditional logic with if statements.

Circuit Diagram

💡Tip: 10k ohms is a sweet spot, strong enough to keep the pin LOW, but not blocking the real signal when the button is pressed.

What You'll Need

Arduino Uno x 1
Breadboard x 1
LED x 1
220Ω Resistor (for LED) x 1
10KΩ Resistor (for Push Button) x 1
Push Button x 1
Jumper wires x 7
USB Cable x 1
Arduino IDE installed

Instructions

Connect the top-right side of the push button to pin 2 on the Arduino.
Connect the bottom-right side of the push button to GND through a 10kΩ resistor.
Connect the bottom-left side of the push button to VCC.
Connect the LED's long leg (anode) of the LED to pin 13.
Connect the short leg (cathode) to GND with a 220Ω resistor.
Connect jumper wires (GND & VCC) from the breadboard to GND & VCC on the Arduino.
Plug your Arduino into your computer using a USB cable.
Open the Arduino IDE, and paste in the code below.
Under Tools, select your board type and COM port.
Click Upload. Press the push button and the LED should turn on!

The Code


// Set up the pins — we're giving them easy-to-use names
const int buttonPin = 2;    // The button is wired to pin 2
const int ledPin = 13;      // The LED is wired to pin 13

void setup() {
  // Tell the Arduino what the pins are doing
  pinMode(buttonPin, INPUT);   // We're going to read the button (so it's an INPUT)
  pinMode(ledPin, OUTPUT);     // We're going to control the LED (so it's an OUTPUT)
}

void loop() {
  // Check if the button is being pressed right now
  int buttonState = digitalRead(buttonPin);  // Reads HIGH when pressed, LOW when not

  // If the button is being pressed...
  if (buttonState == HIGH) {
    digitalWrite(ledPin, HIGH);  // Turn the LED ON
  } else {
    digitalWrite(ledPin, LOW);   // Otherwise, turn the LED OFF
  }

  // This repeats forever — it's the "loop"
}

Schematic Diagram

Schematic diagrams show how current flows and how components connect logically — not just physically.

Alternative Setup: INPUT_PULLUP Explained

You can use INPUT_PULLUP to activate the pull-up resistors built into the Arduino.

This lets your button work without needing a separate resistor on your breadboard.

Normally, when a button isn’t pressed, the input pin can “float” - randomly switching between HIGH and LOW. This causes unstable behaviour.

By enabling INPUT_PULLUP, the pin stays HIGH by default.

When the button is pressed, it connects to GND and pulls the pin LOW — so in your code, you can check for LOW to detect a button press.

Circuit Diagram (INPUT_PULLUP Version)

In this setup, one leg of the button connects to GND, and the other to digital pin 2. No resistor is needed — the Arduino uses its internal pull-up resistor.

Code for INPUT_PULLUP


const int buttonPin = 2;      // Pin connected to pushbutton
const int ledPin = 13;        // Pin connected to LED

void setup() {
  pinMode(buttonPin, INPUT_PULLUP); // Use internal pull-up resistor
  pinMode(ledPin, OUTPUT);          // Set LED pin as output
}

void loop() {
  int buttonState = digitalRead(buttonPin); // Read the button input

  // Logic: Button pressed = LOW (since it's connected to GND)
  if (buttonState == LOW) {
    digitalWrite(ledPin, HIGH);  // Turn on LED
  } else {
    digitalWrite(ledPin, LOW);   // Turn off LED
  }
}

Schematic Diagram (INPUT_PULLUP Version)