BEAM robotics (from Biology, Electronics, Aesthetics and Mechanics) is a style of robotics that primarily uses simple analogue circuits, such as comparators, instead. The 2N2222 is a common NPN bipolar junction transistor (BJT) used for general purpose low-power amplifying or switching applications. It is designed for low to medium. Intro: Getting Started With Relays. This instructable will make you familiar with Relay and its working using a simple circuit.