Every mad scientist’s lab, or teenager’s secret room, needs advanced protection against intrusion by rogue agents or siblings. If you are one of them, you should probably consider getting a Passive infrared (PIR) sensor for you. PIR sensors allow you to detect when someone is in your room when they shouldn’t be.
Though it may seem like something out of a spy movie, you likely use PIR sensors every day. This sensor is the same you will find in most modern security systems, automatic light switches, garage door openers and similar applications where the operation of some electrical device is necessary only in the presence of humans.