SiLOSSiLOS

Motion lights, cameras and dogs all get learned

About this photo
‹ Back
door knocker
1

1The short version

A motion light will absolutely notice a raccoon, a passing car's headlights, or your own dog before it notices an actual stranger, because it isn't watching for trouble, it's just watching for heat that moves. Most low-cost motion detectors can detect motion at distances of about 15 feet, which is a genuinely useful number to know before assuming a fixture covers a whole driveway or yard.

2

2How it actually works

A passive detector, the common cheap kind, contains only a sensor and detects a signature from moving objects via emitted or reflected energy, most often infrared body heat; an active detector adds its own transmitter, using an optical, microwave or acoustic signal it sends out and reads back. The passive kind is what's in nearly every residential motion light, which is part of why they trigger on a passing car's engine heat or a large dog just as readily as a person.

3

3Where lighting fits into security

Security lighting exists specifically to deter or detect intrusions and increase a feeling of safety, and it's used across residential, commercial and institutional settings alike. Motion-triggered lighting is a specific, energy-conscious version of that idea: instead of a fixture burning all night, it saves its brightness for the moment something actually moves, which is both cheaper to run and more startling to whoever triggers it.

4

4What goes wrong

A sensor aimed at a spot the household itself walks past constantly trains everyone to ignore its light, the same habituation problem any alarm system has. A dog, by contrast, doesn't reset on a schedule and doesn't have a fixed 15-foot range, which is exactly why the two get compared in the first place, not because one replaces the other.

Explore this area
HomeHouseGardenFarm