This document describes a sensor switch circuit project submitted by 6 students to their lecturer. It includes an introduction to sensors and sensor circuits. The components used in the circuit are listed. A circuit diagram and PCB design are provided, along with demonstrations of applications. The applications discussed include temperature, IR, ultrasonic, touch, proximity, pressure, and level/smoke/gas sensors. The conclusion discusses how sensor circuits can enable home and industrial automation by controlling electrical loads based on sensor input. References with more information on relay switch circuits, tilt sensors, and light sensors are also provided.