Motion Detection

This page is about mechanical and electronic motion detectors. For motion detection performed by people, animals, or other organisms, see Motion Perception.

Basic Information

Motion Detection refers to technology and processes that can detect or identify movement or moving objects.

Applications for motion detection technology:

• alarm system / burglar alarm
• customer service - lets you know when a customer comes in
• emergency light
• loss prevention - lets you know when a customer (or shoplifter) exits
• occupancy sensor - preventing over-illumination and energy waste
• perimeter defense
• red light camera or other camera that's triggered by motion
• security system
• sentry gun
• surveillance and espionage
• trap

Simple Mechanical Methods

Things a spy might improvise in the field:

• Tripwire - may be observed later to tell if an intruder has been here
• Tripwire with alarm - a tripwire that sounds an alarm when tripped. Could be as simple as soda cans (with some rocks inside) tied to string.
• A hair taped to the inside of a window sill - if the window is opened, the hair breaks free.
• Very full glass of water - put on top of an object, if the object (or glass) is moved it'll spill.
• Windchime or noisemaker on the back of a door - if the door is opened quickly, it'll make noise.

intermediate Methods

• The "nightingale floor" - a Japanese favourite that consists of an expanse of deliberately squeaky floorboards.

Electronic Methods

• Passive Electronic Scans
  • Pyroelectric Infrared Sensor
  • Video Motion Detection (and Video Analytics
• Active Electronic Scans
  • Ultrasound
  • Microwave
  • Laser trigger
  • Dual Technology Motion Detector - uses a Passive Infrared Sensor, which triggers an active sensor. If both score a hit, then it triggers the alarm function. Intended to prevent false alarms.
  • "Pet Immune" motion detector - A modification to other systems so it can't be triggered by motion of objects that weigh less than 80 lbs.

See Also:

• Heat Detector
• Land Mine
• People Sniffer
• Pressure Plate
• Sensors
• Smoke Detector
• Espionage Tropes

Sources

Bibliography

1. Wikipedia on Motion Detection

2. Wikipedia on Motion Detectors

Game and Story Use

• These may be hazards, traps, and alarms that the PCs have to overcome.
• Alternately, the PCs may employ such devices for their own protection.
• Each method has it's own advantages and drawbacks. Some are more easily defeated or triggered than others. Some only record what happened, others scare intruders off, warn authorities, or even take aggressive action.
• The pet-immune sensors are a liability in a setting that has magic, demihumans or robots. Or, indeed, various species of animals such as monkeys and raccoons.
• Likewise, passive infrared sensors are likely to be ineffective against anything close to ambient: undead, constructs, some robots…