Normally Open Reed Switch Magnetic Sensor for Arduino, Raspberry Pi & ESP32

A reed switch magnetic sensor is a simple contact-based proximity sensor that detects the presence of a nearby magnet and changes state for reliable position, door, lid, and limit detection. This normally open sensor remains open until a magnetic field brings the internal reed contacts together, making it useful for alarms, home automation, robotics, and DIY prototyping. Use it as a basic digital trigger with Arduino, Raspberry Pi, or ESP32 projects for cabinet monitoring, end-stop sensing, and non-contact movement detection where low-power, passive magnetic switching is preferred.