PIR sensors allow you to sense motion, almost always used to detect whether a human has moved in or out of the sensors range. They are small, inexpensive, low-power, easy to use and don’t wear out. … They are often referred to as PIR, “Passive Infrared “or “IR motion” sensors.
PIR or Passive Infrared motion sensors are designed to reliably detect people, large pets & other large warm moving objects.
Specifications
PIRs come in many configurations for a wide variety of applications. The most common models have numerous or mirror segments, an effective range of about 10 meters (30 feet), and a field of view less than 180°. Models with wider fields of view, including 360°, are available, typically designed to mount on a ceiling. Some larger PIRs are made with single segment mirrors and can sense changes in infrared energy over 30 meters (100 feet) from the PIR.
Operation
When used as part of a security system, the PIR connected to a detection input zone of the burglar alarm control panel. The system is usually designed such that if no motion is being detected, the relay contact is closed—a ‘normally closed’ (NC) relay. If motion is detected, the relay will open the circuit, triggering the alarm; or, if a wire is disconnected, the alarm will also operate.