PIR Sensor Module HC-SR501

The PIR (Passive Infra-Red) Sensor is a device that detects motion by measuring changes in the infrared (heat) levels emitted by surrounding objects. When motion is detected the PIR Sensor outputs a high signal on its output pin. This logic signal can be read by a microcontroller or trigger a MOSFET which could switch high voltage devices. This is a good sensor for monitoring an area for motion.Both revisions of this sensor use the same Fresnel lens, and basic functionality remains the same between the two (for example you can use the same test programs). However, there were a number of improvements and updates made to Revision B, and if using Revision A in your project the following information should be noted and used.