LED with Arduino Uno R3

Wiring for the LED with 220 Ω resistor on the Arduino Uno R3 (ATmega328P, 5 V logic), chosen with the same pin rules BoardPilot uses: default buses first, and no pins that are used for flash, USB, the debugger or booting.

Wiring

LED pin	Role	Arduino Uno R3 pin	Notes
A	Input to the part	2 (PD2)	Anode (long leg), through the resistor to a GPIO
K	Ground	GND	Cathode (short leg, flat side)

Check before you power it on

The LED is a 3.3 V part and the Arduino Uno R3 uses 5 V signals. Power it from 3.3 V and put a level shifter on the signal wires, or buy a 5 V version of the module.

Test code (Arduino)

void setup() {
  pinMode(2, OUTPUT);  // A on 2
}

void loop() {
  digitalWrite(2, HIGH);
  delay(500);
  digitalWrite(2, LOW);
  delay(500);
}

Arduino board: arduino:avr:uno.

Questions

Which Arduino Uno R3 pins do I use for the LED?

A → 2 (PD2), K → GND.

Does the LED work with the Arduino Uno R3 at 5 V?

The LED is a 3.3 V part and the Arduino Uno R3 uses 5 V signals. Power it from 3.3 V and put a level shifter on the signal wires, or buy a 5 V version of the module.

BoardPilot checks this wiring in 3D as you build it, and finds crossed or missing wires on the real board.

Download BoardPilot

Full Arduino Uno R3 pinout · LED with 220 Ω resistor: all pins and data

The LED on other boards

ESP32 DevKit Arduino Mega 2560 R3 Arduino Nano WeAct Black Pill STM32F411CE ESP32-C3-DevKitM-1 ESP32-S3-DevKitC-1 Nordic nRF52840 DK NUCLEO-F401RE Raspberry Pi Pico 2 Raspberry Pi Pico W Raspberry Pi Pico Teensy 4.1

Other parts on the Arduino Uno R3

BME280 BMP280 DHT22 DHT11 HC-SR04 SSD1306 OLED MPU6050 DS18B20 WS2812B LED strip SG90 servo Relay module HC-SR501 PIR LCD 1602 I2C INA219 VL53L0X BH1750 MAX30102 RC522 RFID NEO-6M GPS Capacitive soil moisture sensor ADS1115 TM1637 28BYJ-48 stepper L298N Potentiometer Push button Joystick module SD card module AHT20