IoT Sensors - Motion Sensors

Motion detectors have been widely used in commercial applications. One common application is activating automatic door openers in businesses and public buildings. Motion sensors are also widely used in lieu of true occupancy sensors to activate street or interior lights in walkways such as lobbies and stairways.bumperSimilar systems have been installed in offices in Shanghai, where the intelligent lighting system senses the activity of people in the office space, whether or not someone is there, sets a time timer, and stops the power supply to save energy if there is no activity for a long period of time.

A passive infrared detector mounted on a circuit board (right) and a photoresist detector for visible light (left). This is the most common type of motion sensing device used in homes and is designed to turn on lights only when motion is detected and the surroundings are dark enough.

Active motion sensors are also known as radar-based motion sensors. They emit radio waves or microwaves in a room or other area that strike a nearby object and reflect it back to the sensor detector. When an object moves in the space controlled by the motion sensor at this point, the sensor looks for frequency shifts in the returning wave that indicate that the wave has hit the moving object. The motion sensor understands these shifts and then sends an electrical signal to the alarm system, lights, or other types of equipment it operates.

Passive Infrared (PIR) motion sensors do not emit any waves, but instead absorb energy to detect changes in surrounding heat emissions. Therefore, these types of motion sensors typically use less energy than active motion sensors that emit energy instead of absorbing it. These types of motion sensors are typically used in home security systems to detect hot bodies such as intruders. In addition, this type of sensor technology can also be found in fire alarms and other sensor-based technologies.

The PIR is a pyroelectric sensor that detects the level of infrared radiation - everything emits some low level of radiation, but the body gives off a lot of heat (spectral).The PIR has two slots made of a special material sensitive to infrared light. When the sensor detects a differential change between the two slots, this generates pulses, and this is the motion it detects.

A radar speed gun (also known as a radar gun and speed trap gun) is a device used to measure the speed of moving objects. It is used in law enforcement to measure the speed of moving vehicles, and is often used in professional spectator sports, such as measuring the speed of a bowling ball in cricket, the speed of a pitching baseball, and the speed of a tennis serve.

A radar speed gun is a Doppler radar unit that may be hand-held, vehicle-mounted or static. It measures the speed of a pointed object by detecting changes in the frequency of the returning radar signal caused by the Doppler effect, which increases in proportion to the approaching speed of the object if the object is approaching, and decreases if the object is receding.

Tomographic Motion Detection (TMD) sensor utilizes radio waves to identify any disturbances in the surrounding area. It works by surrounding an area with nodes that communicate with each other via radio waves to create a mesh network. Relying on the mesh network of disturbances to detect motion in the area, each network has a Processing Unit (PU) that has normally closed contacts for easy integration with any standard panel.

Unlike many other types of sensors, tomographic sensors can detect movement of objects and through walls, making them ideal for large spaces or areas with many static obstacles. These types of motion sensors are expensive and are typically used in commercial security systems, a sight we often see in some movie bank robbery sequences.

These types of motion sensors utilize magnetic sensors that are triggered upon obstruction or separation. Motion sensors such as these are typically used for doors and windows by placing a pair of magnets on the door/window and the accompanying frame. Thus, when the door/window is opened, the magnetic bond breaks and the sensor then triggers. These types of sensors are usually inexpensive and easy to install, making them easily accessible and widely used.

These types of door magnetic sensors are available for sale on major e-commerce sites at affordable prices, making them a great choice as a home security measure.