Different Types Of Motion Sensors

Last updated: December 8, 2022


To protect your loved ones and precious belongings, it is recommended to have a security system in your home. And the key component of any smart home security system is a motion sensor, as it allows you to detect when someone is inside your house when they shouldn’t be. 

Did you know that burglaries are officially defined as “unlawful entry of a structure to commit a felony or theft”? The FBI estimates that over 1 million burglaries occur annually in the United States. In fact, burglary is so common that it occurs every 26 seconds, which amounts to approximately 3,300 per day. However, a lesser-known fact is that in 85% of burglaries, the crime is committed by amateurs — often done by someone desperate. Unfortunately, they usually get away with it, as less than 30% of homes have an effective security system installed. 

If you are interested in knowing more about the different types of motion sensors, continue reading this article.

How Do Motion Sensors Work

How Do Motion Sensors Work

A motion sensor, sometimes known as a motion detector, is a piece of device that uses a highly-sensitive sensor to detect nearby individuals or objects. They are mainly utilized in security systems for residential and commercial properties. However, many other industrial fields employ them for a variety of reasons aside from security, which include:

  • Opening and closing automatic doors
  • Turning on and off automatic water faucets and toilets
  • Turning on lights when a person enters a room
  • Turning off lights when a room is empty
  • Controling ATM displays
  • Operating automatic ticket gates
  • Augmenting virtual reality systems

Generally, embedded systems for most motion sensors consist of three main parts: mechanical hardware, a processing computer, and a sensor unit. Because motion sensors can be configured to carry out incredibly specialized tasks, these three components come in various sizes and configurations. 

Different Types Of Motion Sensors

Motion sensors are used to detect when a potential intruder is near or was able to break into your house. At the same time, it can also alert you of their unauthorized presence by syncing with your floodlights or your security alarms. 

There are three main types of motion sensors: 

  • Active Ultrasonic Sensors
  • Passive Infrared Sensors (PIR)
  • Dual Technology Sensors

Active Ultrasonic Sensor

Active sensors have both a transmitter and a receiver. By monitoring changes in the amount of sound or radiation reflected back into the receiver, active ultrasonic sensors can identify motion. 

Particularly, they do this by emitting ultrasonic sound waves at frequencies higher than those heard by humans. These waves then bounce off objects or persons in the immediate vicinity and return to the motion sensor. The sensor’s internal transducer, which transmits the pulse and receives the echo, serves as a waypoint for the signal. 

By monitoring the duration between sending and receiving the signal, the sensor can estimate how far away the target is. When the target interrupts or alters the sensor’s field, an electric pulse is sent to the processing computer, which in turn, interacts with the mechanical hardware.

Other general kinds of active ultrasonic sensors include microwave sensors (which utilize microwave pulses and radiation) and tomographic sensors (which transmit and receive radio waves). 

Passive Infrared Sensor (PIR)

In contrast to an active motion sensor, a passive motion sensor does not have a transmitter. This type of sensor detects motion based on a perceived increase in radiation in its environment rather than recording a steady reflection. A PIR is designed to recognize the natural infrared light the human body emits. Only infrared is permitted to pass through the filter that houses the receiver. The difference in radiation caused by a person walking within the PIR sensor’s range of detection generates a positive charge inside the receiver. This perceived change in temperature prompts the sensing unit to communicate electrical data to the hardware component and embedded computer.

Additionally, as the PIR motion sensor detects heat in its surrounding areas, it creates a protective grid. The infrared sensor triggers an alarm when a moving object or person blocks too many grid zones and causes a rapid change in the infrared energy levels of the protective grid. 

Dual Technology Motion Sensors

In an effort to decrease false alarms, some motion sensor units integrate multiple detecting methods. A passive infrared sensor and an active ultrasonic sensor, for instance, are frequently used together in dual technology motion sensors. 

Each sensor type operates in different areas of the spectrum (from passive to active). Because both sensors must trip in order for an alert to be set off, dual-technology motion sensors are less likely than other types to cause a false alarm.

Are you interested in purchasing your own taser device? Find out how they work and how you could use them for self-defense in this article by Security Forward.

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