Set up the Arduino IDE and blink an LED

Every electronics journey starts with a blinking LED. In this lesson you install the Arduino IDE, connect your UNO R3 board and upload your first program, called a sketch.

What you'll learn

• How to install the Arduino IDE and select your board
• The structure of an Arduino sketch: setup() and loop()
• How to wire an LED safely with a resistor on a breadboard

What you need

• UNO R3 board and USB cable
• Breadboard
• 1 LED (any colour)
• 1 resistor, 220 Ω
• 2 jumper wires

Step 1: Install the Arduino IDE

1. Download the Arduino IDE from arduino.cc/en/software and install it.
2. Connect the UNO R3 to your computer with the USB cable. The green power LED on the board lights up.
3. In the IDE, open Tools → Board and choose Arduino Uno.
4. Open Tools → Port and choose the port that appeared when you plugged in the board (for example COM3 on Windows or /dev/cu.usbserial… on a Mac).

If no port appears, your board may use a CH340 USB chip. Install the CH340 driver for your operating system, then reconnect the board.

Step 2: Wire the LED

An LED has a long leg (the positive anode) and a short leg (the negative cathode). The resistor limits the current so the LED and the board pin aren't damaged.

Step 3: Upload the sketch

const int LED_PIN = 8;

void setup() {
  pinMode(LED_PIN, OUTPUT);   // pin 8 drives the LED
}

void loop() {
  digitalWrite(LED_PIN, HIGH); // LED on
  delay(500);                  // wait half a second
  digitalWrite(LED_PIN, LOW);  // LED off
  delay(500);
}

Click Upload (the right arrow). After a few seconds the IDE says "Done uploading" and your LED starts blinking.

How it works

setup() runs once when the board starts. loop() then runs again and again, forever. digitalWrite() switches the pin between 5 V (HIGH) and 0 V (LOW), and delay() pauses for a number of milliseconds.

Try this next

• Change both delays to 100 to make the LED blink fast.
• Add a second LED on pin 9 and make the two LEDs blink in turn, like a railway crossing.

Troubleshooting

• Upload fails: check that the right board and port are selected under Tools.
• LED stays off: turn the LED around. It only conducts in one direction.