About This Project
A PIR module is basically made of a pyroelectric sensor (see it below as the round metal can with a rectangular crystal in the center), which can detect levels of infrared radiation. Everything emits some low level radiation, and the hotter something is, the more radiation is emitted. The sensor in a motion detector is actually split in two halves.
The reason for that is that we are looking to detect motion (change) not average IR levels. The two halves are wired up so that they cancel each other out. If one half sees more or less IR radiation than the other, the output will swing high or low.
This give us 2 options for powering it up: using the existing 5V pin or if you want to use it in a 3V only setup, just bypass or remove the regulator and that’s it.
Connecting the PIR sensor module is pretty trivial, as it has only 3 PIN: GND, DOUT and VCC. The PIR acts as a digital output so all you need to do is listen for the pin status change to HIGH (motion detected) or LOW (no motion detected).
Blink a LED when movement detected