🤖 First Arduino Blink

Write your very first program and make a light blink, just like real engineers do!

Inventor⏱️ 1 hour (plus setup)

🧰 What you need

1 Arduino Uno or Uno-compatible board
1 USB cable that fits the board
A computer with the free Arduino IDE (a grown-up should install it)
Optional: 1 LED, 1 220 Ω resistor, 2 jumper wires, a breadboard

🔧 Let's build it!

With a grown-up, install the Arduino IDE from the official Arduino website and plug in your board.
In the IDE, pick your board type (Arduino Uno) and the port it's plugged into.

Type this program:

void setup() {
  pinMode(13, OUTPUT);     // pin 13 will send power out
}

void loop() {
  digitalWrite(13, HIGH);  // light ON
  delay(500);              // wait half a second
  digitalWrite(13, LOW);   // light OFF
  delay(500);              // wait again
}

Click the Upload arrow. After a moment, the tiny LED marked "L" on the board blinks!
Change both delay(500) numbers to 100. Upload again. Super fast blinking!
Bonus: unplug USB, put an LED and a 220 Ω resistor on a breadboard from pin 13 to GND (long LED leg toward pin 13). Plug back in and watch your own LED blink.
Challenge: can you make it blink S-O-S in Morse code?

🔬 What's happening?

An Arduino is a tiny computer called a microcontroller. Your code tells it to switch pin 13 between HIGH (about 5 volts, ON) and LOW (0 volts, OFF). Inside the chip, transistors (tiny electronic switches) do the switching millions of times faster than you could flip a light switch. setup() runs once when the board starts; loop() repeats forever. The resistor limits the current so your LED doesn't burn out (check the Ohm's law calculator in The Lab!).

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