Arduino is a small microcontroller board with a USB plug to connect to your computer and a number of connection sockets that can be wired up to external electronics such as motors, relays, light sensors, laser diodes, loudspeakers, microphones, and other items. They can either be powered through the USB connection from the computer, or from a battery or other power supply. They can be controlled from the computer or programmed by the computer and then disconnected and allowed to work independently.
An Arduino Uno board The board design is open source. This means that anyone is allowed to make Arduino-compatible boards. Such competition has led to low costs. The basic boards are supplemented by accessory shield boards that can be plugged on top of the Arduino board. In this book, we will use three shields: the USB master shield that allows us to connect to Android devices over USB; a motor shield for driving the wheels of a little robot and an Ethernet shield.