Home Security: The Motion Detector

motion-detectorIn an age where crimes and burglary attacks are rampant, securing one’s home is a top priority of home owners. Home security has advanced beyond mere locks and bolts. This is the era of home automation. An automated house is one in which every device or system can be accessed, operated and controlled from a mobile device via Ethernet or Wi-Fi. The motion detector or sensor is a noteworthy example of an automated home security system.

The motion detector is a device capable of ‘detecting’ motion and alerting the necessary personnel. The user of a motion detector sets it to detect moving objects, especially people, and signal the user.

How Does It Work?
Motion detectors are usually placed around doors and windows and are activated or ‘armed’ most times at night. It makes use of either one or a combination of multiple technologies to detect movement around such areas. Once movement is detected, the sensor is tripped and a signal is sent to the security system’s control panel and then to the monitoring centre which could be the user’s mobile device, if the user is not home. Thus, the user is alerted to a potential threat or burglary attack in his home. This is the beauty of home automation.

Technologies Employed
The technologies used in motion detectors include:

Passive Infrared (PIR) technology
This is the most widely used technology in motion detectors. Humans emit black body radiation at mid-infrared lengths. Passive infrared sensors are sensitive to and can detect this radiation within a specified distance. PIR sensors do not emit any energy or radiation, hence the name ‘passive’.

Microwave (MW) technology
Motion detectors using this technology can cover a larger area than the PIR sensors. However, they are susceptible to electrical interference and are generally more expensive. The working principle involves sending out continuous microwave pulses and measuring the phase shifts reflection of such pulses off a moving object.

Ultrasonic Technology
This technology is similar to the MW technology, but instead of emitting microwave pulses, the detector emits ultrasonic waves and measures the reflections off nearby moving objects. A major drawback of ultrasonic sensors is their sensitivity to motion even in areas not required. This is often due to reflections of the ultrasonic (sound) waves around corners.

Dual Technology
Most modern motion sensors combine features of two separate technologies in an effort to reduce false triggering and alarms. Usually, the PIR technology is combined with the MW technology. In this case, for an alarm to be triggered, the two separate sensors must trip together. This lowers the possibility of false alarms.

Some detectors combine the motion detection with video camera features. Once motion is sensed or detected, the camera is immediately triggered and starts recording.

Motion detectors should be mounted or installed in areas where there are no heating vents, around the stairs and hallways to increase their effectiveness. The motion detectors are clever ways of stalling, disrupting and preventing intruders and burglary attacks on homes. Thus, they are essential features of a home security system.