PIR Sensor
HC-SR501 PIR Sensor
The PIR sensor stands for Passive Infrared sensor. It is a low cost sensor which can detect the presence of Human beings or animals. This HC-SR501 PIR sensor module has three output pins Vcc, Output and Ground as shown in the pin diagram above.
HC-SR505 PIR Motion Sensor Module
HC-SR505 is mini PIR (Passive Infra Red) motion sensor module, which as the name implies used for detecting the motion of a body in front of it.