Why PIR Sensors Detect Human Motion
PIR sensors are everywhere in smart homes: hallway lights, night lights, security triggers, bathrooms, cabinets, and battery-powered motion sensors.
They are cheap, mature, and low power. They are also often misunderstood.
A PIR sensor is not a camera. It does not know whether an object is a person. It is also not a mmWave radar that can observe tiny body motion over time.
The first model is: a PIR sensor detects changes in infrared heat radiation across its field of view. It is good at detecting human motion, not at proving continuous still presence.
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