Sensors are your eyes, ears, noses, and fingertips when it comes to exploring and measuring the physical world. Together with the microcomputers Arduino and Raspberry Pi, it is easy to programmatically capture sensor readings, process them, and output results or trigger actions. In this book, you will learn to build simple devices that can measure a wide range of things, from detecting various gases to infrared light and the acceleration of objects. Among other topics, the following subjects and projects from the physical world are covered: - Measuring distances with ultrasound and infrared - Gases and smoke: breathalyzer and smoke detector - Touch and pressure: contactless touch sensor - Detecting and controlling motion - Light and flames: building a chameleon dome - Acceleration and angular velocity: a robotic hand.