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The Arduino Uno R3 is a highly popular, open-source microcontroller board based on the Microchip ATmega328P processor. It is widely considered the standard entry-level board for beginners and hobbyists getting started with electronics, robotics, and coding, while remaining robust enough for advanced prototyping.
The “R3” designation stands for Revision 3, which brought several circuit enhancements, a stronger reset mechanism, and an upgraded ATmega16U2 chip to handle USB-to-serial communication.
| Parameter | Specification |
| Microcontroller | ATmega328P (8-bit AVR architecture) |
| Operating Voltage | 5V |
| Input Voltage (Recommended) | 7V to 12V (via barrel jack or VIN pin) |
| Input Voltage (Limits) | 6V to 20V |
| Digital I/O Pins | 14 (of which 6 provide PWM output) |
| Analog Input Pins | 6 (10-bit resolution) |
| DC Current per I/O Pin | 20 mA (40 mA absolute maximum) |
| Flash Memory | 32 KB (0.5 KB used by the bootloader) |
| SRAM | 2 KB |
| EEPROM | 1 KB |
| Clock Speed | 16 MHz |
Digital Pins (D0–D13): Used for digital inputs (like button presses) and digital outputs (like turning on an LED).
PWM Pins (~3, ~5, ~6, ~9, ~10, ~11): These 6 digital pins can simulate analog outputs (e.g., dimming an LED or controlling a servo motor) using Pulse Width Modulation.
Analog Input Pins (A0–A5): Used to read varying voltage levels from analog sensors (like potentiometers, light sensors, or temperature sensors).
Dedicated Communication Pins: Includes hardware support for UART (Serial via pins 0/RX and 1/TX), I2C / TWI (SDA and SCL pins next to AREF), and SPI (pins 10, 11, 12, 13).
Replaceable Chip: The official board uses a Dual-In-line Package (DIP) IC. If you accidentally short-circuit and fry the microcontroller, you can easily pop it out and replace it for a few dollars rather than buying a whole new board.
USB Overcurrent Protection: It features a resettable polyfuse that protects your computer’s USB ports from shorts or overcurrent situations by automatically tripping if more than 500 mA is drawn.
Power Versatility: It can be powered directly through a USB Type-B cable connected to a computer, an external AC-to-DC adapter (wall wart), or a 9V battery via the 2.1mm center-positive barrel jack.
The Uno R3 is fully supported by the standard Arduino IDE (Integrated Development Environment) and the Web Cloud Editor. 1 Because it features a pre-programmed bootloader, you can upload new code via the USB cable without needing an external hardware programmer. 2
