Lesson 2 of 16

Blink an LED

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const int LED_PIN = 13; void setup() { pinMode(LED_PIN, OUTPUT); } void loop() { digitalWrite(LED_PIN, HIGH); delay(500); // how long it stays on digitalWrite(LED_PIN, LOW); delay(500); // how long it stays off }

Stopped · Your code isn't running yet. Until you press Run, the board runs the program already on it.

Nothing printed yet. Press Run.

Your first circuit: an LED and a resistor on the breadboard, driven by pin 13. Change the timing and the resistor and see what each does.

Run it and watch both LEDs blink
Swap the resistor and see the brightness change
Break it: take the resistor out in Break it

Pin	Connects to	What it does
`D13`	Resistor, then the LED's long leg	Switches the LED: HIGH lights it.
`GND`	The LED's short leg	Where the current goes back to.

Wire it in

Sensors and actuators this board drives, with the real connections.

LEDSupply 5 V
Anode (long leg) toward the pin, cathode to GND, with a 220 Ω to 1 kΩ resistor in series.
Part pin Board pin
A D13Wire colour orange
K GNDWire colour black
Careful
Never without the resistor: the pin would try to push over 100 mA through the LED.

Part pin	Board pin
A	D13Wire colour orange
K	GNDWire colour black

All 16 parts on the Arduino Uno R3 page

Blink an LED

Try it yourself

Serial monitor

Checks

Break it

Parameters

Wire it in

Blink an LED

Try it yourself

Serial monitor

Checks

Break it

Parameters

Wire it in