Clear the bench
Open the editor. The first time, it opens on this very circuit, already built: an Uno blinking an LED, called First blink. Press Run to see it, then start from scratch: open the â–¾ beside Save and choose New for an empty canvas, or select everything with Ctrl/Cmd+A and press Delete.
Put a breadboard and a board down
Press + on the canvas toolbar, or the A key. The part panel opens docked
on the left, with a search box and a category rail. Type breadboard, then drag
the tile onto the canvas, or click it to drop it at the middle of the view.
Do the same for Arduino Uno. The Uno does not push into a breadboard: its
headers are two inches apart, which is wider than the board is, so it sits
beside the breadboard and is wired to it with jumpers, exactly like the real
thing.
The LED and its resistor
Add an LED and a resistor, and drop both onto the breadboard so their pins land in holes. A breadboard strip is five holes long, so two pins in the same strip are the same net. Put the LED's cathode and one end of the resistor in the same strip.
Select the resistor. The properties panel opens beside it with its value in ohms; 220 is the usual choice for an LED on 5 V. Select the LED and you can pick its color.
Wire it
Drag from the Uno's 13 pin to the strip the LED's anode is in, and from the free end of the resistor to a GND pin. While you drag, the hole or pin under the pointer gets a ring and its name, so you can see what you are about to land on. Let go and the wire is drawn with square corners you can drag afterwards.
Nothing needs a power rail here: the Uno drives the LED from its own pin.
Write the sketch
The right-hand pane is now the Uno's project. Replace what is in sketch.ino
with this:
void setup() {
pinMode(13, OUTPUT);
}
void loop() {
digitalWrite(13, HIGH);
delay(500);
digitalWrite(13, LOW);
delay(500);
}
Run it
Press Run. The first build downloads the compiler once and caches it, so it takes a little while; builds after that are quick. A line across the top of the code says what the compiler is doing. If there is an error, that line stays; press it to jump to the line in your sketch, or press the chevron at its end for the full log.
The LED blinks once a second and the header readout settles near 1.00x, which
means the simulated circuit is keeping pace with real time.
If it does not work
- The LED stays dark. Check that the LED's longer leg (the anode) is in the strip wired to pin 13, and that the resistor's other end reaches GND. An LED in backward does not light.
- Nothing happens on Run. Look at the line across the top of the code: a build error stops the run, and pressing the line takes you to it.
- A wire will not attach. See a wire will not connect.
Keep it
Press Save. Signed out, that writes to this browser. Signed in, it also writes to your account, and Share gives you a link to send someone.
Next: save, share, and come back. For more on the editor itself, see placing parts, wiring and the Arduino Uno model.