PIR sensors, or Passive Infrared sensors, detect motion by sensing changes in infrared radiation emitted by warm objects, making them ideal for motion detection applications.
What are you wanting to automate?
Using PIR’s to automate anything is not as easy as it seems.
For example if you hook your lights up to activate when the PIR is triggered you will probably need to be running a timer (think those annoying toilets) to then turn them off.
If its on a timer you will need to keep triggering the PIR to keep the lights on.
PIR’s are designed to trigger by an infra red source moving across the device .
The old PIR’s could be walked directly up to head on without triggering.
So for example if you set your lounge room lights to turn on after a PIR triggers and then you went and sat on your couch, your lights would probably turn off after the timer say 5mins despite you being in full view of the PIR.