First steps with Arduino Uno · Lesson
8 min read
Meet the Arduino Uno
A tour of the board: microcontroller, headers, power pins and the built-in LED.
What You Will Learn
- Find the digital, analog and power headers
- Know the board's limits (5 V, 20 mA per pin)
- Explore pins in 3D
The Arduino Uno R3 is built around the ATmega328P, an 8-bit microcontroller running at 16 MHz with 32 KB of program memory and 2 KB of RAM. It runs one program — your sketch — over and over.
Highlighted Pins on arduino-unoD13, D9, A0, V5, GND1
Key pins: D13 (built-in LED), D9 (PWM), A0 (analog), 5V and GND.
- Digital pins 0–13: on/off inputs and outputs. Pins with ~ (3, 5, 6, 9, 10, 11) can do PWM.
- Analog pins A0–A5: read voltages from 0 to 5 V as numbers 0–1023. They can also be digital pins 14–19.
- Power: 5V and 3.3V outputs, GND, and VIN for an external supply.
- Pins 0 and 1 are the serial port to your computer — avoid them while using Serial.
Each pin can safely supply about 20 mA (40 mA absolute maximum). Motors, relays and long LED strips need a driver or transistor.
Open Boards → Arduino Uno to rotate the 3D model and click any pin for details.
Check Your Understanding
Test what you learned in this lesson