This is the best HC SR501 PIR Motion Sensor for all purpose security system. All live objects whose body temperature is more than 0 degree Celsius emits the heat in form of infrared radiation through their body. This radiated signals are invisible to human eye. These signals can be detected by using PIR sensor which is specially designed for such purpose. In passive infrared (PIR) sensor, passive word indicates PIR sensor does not generate or radiate any energy for detection purposes. PIP sensors don?t detect or measure ?heat?, they detect the infrared radiation emitted or reflected from human or animal.
There are two potentiometers on PIR motion sensors board: Sensitivity adjust and time delay adjust. It is possible to make PIR more sensitive or non sensitive enough. The maximum sensitivity can be achieved up to 6 meters. Time delay adjust potentiometer used to adjust the time period tsel shown in above timing diagrams. Clockwise movement leads PIR more sensitive.
Pin 1 ? gnd we have to connect this pin to ground.
Pin 2 ? output this pin gives output (3. 5v) when the motion is detected.
Pin 3 ? vcc this pin provides supply voltage ( plus 5v) to pir element and internal circuit.