Reading the state from an infrared motion sensor

Alarm systems using motion sensors are a ubiquitous part of our society. With our Raspberry Pi, they are incredibly easy to build. We will cover the following in this section:

• What is a PIR sensor?
• Using the GPIO buzzer class
• Building a basic alarm system

What is a PIR sensor?

PIR sensors, a type of motion sensor, are used to detect motion. Applications for PIR sensors are pretty much based on detecting motion for security systems. PIR stands for passive infrared, and PIR sensors contain a crystal that detects low-level radiation. PIR sensors are actually constructed in two halves, as it is the difference between the halves that detects motion. The following is a photo of...