Residential Security, Access Control, and Surveillance Copyright © 2005 Heathkit Company, Inc. All Rights Reserved Presentation 3 – Motion Detection

2 Objectives At the end of this presentation, you will be able to:

3 Explain how infrared light is used in motion detection. Explain how microwaves are used in motion detection.

4 Passive Infrared (PIR) Motion Detection Operates in the far infrared region. Tuned to “see” human body heat in the 9.4 micrometer wavelength (93° F skin temperature). Uses multiple Fresnel lens to focus IR waves on the detector. Responds to changes in IR levels to filter background IR noise. Most efficient seeing movement across its field of view.

5 The Fresnel Lens Plano Convex Lens, Edge View Fresnel Lens, Edge View Fresnel Lens, Front View

6 Modifying the Fresnel Lens Normal Fresnel Lens Modified Fresnel Lens

7 IR Detector Lens

8 Focusing Light on the Detector IR Detector Multiple Fresnel Lens

9 One Lens Limits Detection IR Detector Single Fresnel Lens IR Detector Output

10 IR Detector Output IR Detector Array of Fresnel Lens Multiple Lenses Enhance Detection

11 PIR Troubles Motion directly at the PIR is difficult to detect. High ambient temperature may mask the heat signature of an intruder. Small animals can cause false triggers. Rain, snow, and sun can mask an intruder from an exterior-mounted PIR.

12 Microwave Motion Detectors Operates in the low microwave region. Works like a doppler radar to detect motion. Not affected by heat, rain, or snow. Does not require a lens or reflector to focus the microwaves leaving or entering the detector. Most efficient seeing movement directly at, or away from the detector.

13 Microwave Detector Operation PIR Circuit Board Microwave Antenna Burst of Microwaves Intruder

14 Intruder PIR Circuit Board Microwave Antenna Reflected Microwaves

15 Doppler-Effect Motion Detection Transmitted Microwave Signal Burst Object Moving Toward Antenna Object Not Moving or Moving Laterally Object Moving Away From Antenna Reflected Microwave Signal Burst

Degree Area of Coverage PIR Circuit Board Microwave Antenna Microwaves

17 Microwave Troubles Lateral motion is difficult to detect. Any type of motion from solid objects, including small animals, window curtains, flags, and blowing leaves can cause false triggers. Short-range detection only to meet FCC regulations. Can cause interference with radio and telephone communications, and with television reception.

18 A Few Parting Thoughts There are two common types of PIR detectors. External devices used to switch on lights for security or convenience. Internal devices used for security monitoring with outputs tied back to the security controller. Microwave detectors are usually combined with internal PIR detectors to provide a more secure detection system.

Residential Security, Access Control, and Surveillance Copyright © 2005 Heathkit Company, Inc. All Rights Reserved End