Passive Infrared Sensor which uses the IR to detect the motion. It detects an object that has moved in or out of the sensor range.
- PIR is basically made up of a pyroelectric sensor.
- The round metal with a rectangular crystal in the center, which can detect the level of infrared radiation.
- The sensor in a motion detector is actually split into two halves.
- When the sensor is idle, both slots detect the same amount of IR.
- When motion detected it first intercepts one half of the PIR sensor.
- When the warm body leaves the sensing area, the reverse happens, whereby the sensor generates a negative differential change.
- The PIR detects motion, the output pin will go “high” to 3.3V.
- PIR Sensor.
- PIC16f877a MicroController.
- Vcc: +5v.
- OutPut: 3.3v.