Motion detector

Such a device is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area.

An active electronic motion detector contains an optical, microwave, or acoustic sensor, as well as a transmitter.

Changes in the optical, microwave or acoustic field in the device's proximity are interpreted by the electronics based on one of several technologies.

Motion can be detected by monitoring changes in: Several types of motion detection are in wide use: Passive infrared (PIR) sensors are sensitive to a person's skin temperature through emitted black-body radiation at mid-infrared wavelengths, in contrast to background objects at room temperature.

[3] This distinguishes it from the electric eye for instance (not usually considered a motion detector), in which the crossing of a person or vehicle interrupts a visible or infrared beam.

RF tomographic motion detection systems may use dedicated hardware, other wireless-capable devices or a combination of the two.

Other wireless capable devices can act as nodes on the mesh after receiving a software update.

[8][9] This solution is particularly attractive when the intent is to record video triggered by motion detection, as no hardware beyond the camera and computer is needed.

[10] Photodetectors and infrared lighting elements can support digital screens to detect hand motions and gestures with the aid of machine learning algorithms.

[citation needed] Often, PIR technology is paired with another model to maximize accuracy and reduce energy use.

A motion detector attached to an outdoor, automatic light
A passive infrared detector mounted on circuit board (right), along with photoresistive detector for visible light (left). This is the type most commonly encountered in household motion sensing devices and is designed to turn on a light only when motion is detected and when the surrounding environment is sufficiently dark.