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Built-in project · Arduino Uno R3

Arduino Uno blink

Flashes an LED on pin 13 once a second: the smallest thing an Arduino Uno can do, wired on the breadboard beside it. The whole build, an Arduino Uno and 2 more parts, runs here in your browser on the firmware below; open it in the editor to change the wiring or the code and run it again.

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Arduino Uno blink · Arduino Uno R3live0.000 s 0.00x
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The circuit itself, running here on the simulator. Press what can be pressed; click anything else to open it in the editor.

The code

The firmware exactly as the editor opens it. Change a line there and press Run: it compiles in the browser.

sketch.ino · Arduino Uno R3
// Blink: the smallest thing a board can do.
//
// Pin 13 has the LED soldered next to the USB socket, so LED_BUILTIN is 13.
// Wire an LED and a 220 ohm resistor from pin 13 to GND to see it on the
// breadboard too.
//
// delay() puts the chip to sleep between timer ticks rather than spinning, so
// this sketch costs the simulator almost nothing while it waits.

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
  digitalWrite(LED_BUILTIN, LOW);
  delay(500);
}

Parts list

4 parts, plus the jumper wires. Every one is in the editor's parts bin.

How it is wired

3 connections, pin by pin, read from the circuit itself. Each line is one set of pins joined together, by a jumper wire or a breadboard strip.

  • Ground: Arduino Uno R3 pin GND; LED, red pin C
  • Arduino Uno R3 pin 13; Resistor, 220 Ω pin 1
  • Resistor, 220 Ω pin 2; LED, red pin A

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