Motion Detectors (Passive Infrared)

Chris Bent

Electronic sensor that measures infrared (IR) light

Do not detect motion; detect changes in temperature

Emits nothing; it’s “passive” ◦ Responds infrared energy radiated by the object

About Passive Infrared (PIR)

Small Inexpensive Low-Power Easy to Use Don’t Wear Out

Continued…

Pyroelectric Sensor: detect levels of infrared radiation

Looks to detect motion (change) not average IR levels

How it Works

Humans skin temperature is about 93° F, and radiate infrared energy with a wavelength between 9 and 10 μm◦ The sensors are sensitive in the range of 8 to 12

μm Plastic Housing limits the wavelengths to 8-

14 μm

Sensitivity

Layout

Suitable for Enclosed Spaces Burglary Alarm Systems Cameras Office lighting

Uses

PIR

Camera

Do It Yourself…

http://www.ladyada.net/learn/sensors/pir.html