HCSR501 PIR Motion Sensor Detector module is used to detect motion generally, the motion of humans within the range of the sensor. It has three pins i.e., Vcc, Dout (High/Low output) and Ground. This module works on 5V DC hence Vcc is supplied with 5V DC. Dought is an output pin. It gives 0V when idle i.e., no motion is detected. 3.3V is retrieved as output from Dout when it detects motion within the range. The range of the HCSR501 PIR motion sensor is 120° and 7 meters. This module can distinguish between human motion and object motion. Operating temperature of the module ranges from -20°C to 80°C. There are two potentiometers in the module to control the sensitivity of the sensor. The detection distance can be increased or decreased using a potentiometer while the delay time can be increased or decreased using the other potentiometer. This module has two working modes. Repeatable mode(H) and Non-Repeatable mode(L). In Repeatable mode, will supply a high signal for a particular time once it detects a motion in its range and then goes low. But in Non-Repeatable mode goes high once it detects any motion and remains high for the time the object of which motion was detected remains in the range of the sensor. This module is usually used for automatic lights, security systems and in many other machines for automation. This PIR sensor is often referred to as “PIR”, “Pyroelectric”, “Passive Infrared” and “IR Motion” sensor.