Motion Detector

With the advancement in the ways Burglars give shape to their actions, Conventional Security Systems like CCTV can not stand still to provide any security to people. To cope up with this problem, advanced security devices have been devised and one of the most reliable products is Motion Detector.

What is a Motion Detector ?

A Motion Detector is an electronic device with Motion Sensors in it that work in mechanisms designed to measure the movement in its vicinity. Though a motion detector is used for many different purposes like Automated Lights, Hand Dryers, Automatic Doors but the most vital role is played by it when integrated with Intrusion Detection Systems.

A Motion Detector works because of the presence of a Motion Sensor in it which notices the moving objects, mainly people in its detection range. The Motion Detector senses an unauthorised person moving in its range and sends an alert to the control system to act upon.

Types of Motion Detectors :

1. Active Motion Detectors

Active Motion Detector

Active Motion Detectors are called Radiation based detectors as they emit radiations or electromagnetic waves (Radio waves or Microwaves) to detect the motion. They are named Active because they perform both the activities i.e. transmit as well as receive the radiations. The Active Motion Detectors detects motion by measuring the difference in the energy transmitted and received after being reflected by any object. The detector keeps on sending and receiving the waves continuously and when there is any interruption in its path by any moving object, the number of waves reflecting back get affected which activates an electric pulse to be sent to the microcontroller. The microcontroller takes this pulse as a warning signal and sends an alert to the Security System indicating intrusion activity.

Applications -

  • Proximity Sensors
  • Products Detector
  • Intrusion Detection System
  • Automatic Doors
  • Automated Lights

Advantages -

  • The Active Motion Detectors do not need to be in contact with the object to detect it.
  • These sensors work fine and detect objects even in dark.
  • The sensors are energy efficient and thus produce less electricity bills.
  • They are secure modes of communication due to point to point interaction between the transmitter and the receiver.
  • The sensors are compact and can be installed easily at premises of all types.

2. Passive Motion Detectors

Passive Motion Detector

Passive Motion Detectors are also called Passive Infrared Detectors. They are named passive because, unlike Active Motion Detectors, Passive Motion Detectors do not emit any radiation. Instead, they just receive and measure the heat released by an object in the form of Infrared waves. The Passive infrared sensor enabled motion Detector when installed at a place keeps on scanning the whole area in its detection range and remembers the heat maps of the complete area. Whenever any unauthorised person enters the guarded place, the PIR motion sensor senses the change in the Infrared level and sends an electric signal to the embedded computer system. The system then sends a warning to the Control Panel of the Alarm System which then acts as per its programmed settings.

Applications –

  • Burglar Alarm Systems or Intrusion Detection System
  • Automated Home Appliances
  • Automated Doors
  • Parking Areas
  • Automated Lightings
  • IR Thermometers
  • Night Vision Cameras
  • Gas Analyzers
  • Moisture Analyzers
  • Smoke and Fire Detectors

Advantages –

  • Passive Motion Detectors detect the objects even in dark without any failure.
  • The detectors can identify the objects without being in physical contact.
  • The sensors are easy to install without requiring much wiring and technical knowledge.
  • The sensors consume less power and hence batteries last for a long duration.

3. Microwaves Motion Detectors

Microwaves motion detectors use the Microwaves of the Electromagnetic spectrum for detecting the motion of humans and objects. Microwaves detectors are composed of two components arranged side by side of each other. The first component is a microwave transmitter and the second is a receiver. The transmitter emits the microwaves continuously in its surroundings which then get reflected by a stationary object in front and reflected back to the receiver. This sending and receiving workflow keep on going until any human or object comes in between the path of the waves. When the path of waves gets disturbed, the reflected amount of waves gets changed and the receiver reacts to the change. The disturbance thus created by the object is considered as an indicator of intrusion attempt making the detector to send a warning signal to the control panel.

Advantages –

  • Microwaves sensors are resistive to harsh weather conditions.
  • They have a wide coverage range.
  • They are very sensitive in detecting motion.
  • Microwaves sensors are not affected by the interference of other devices.
  • Microwaves sensors are dust and smoke proof.

Applications –

  • Intrusion Detection System
  • Automatic Industrial Doors
  • Automatic Lighting
  • Remote Sensing
  • Speed Guns

4. LiDAR (LASER) Motion Detectors

LiDAR (LASER) based motion detectors work on the principle of LASER for detecting the motion of objects in their surroundings. LASER is a device that emits a narrow beam of light produced by Optical Amplification. The devices working on the principle of LASER emit the light rays in a straight line that travels in the air as a transmission medium and hits the object opposite to it regularly. If someone comes into its path, the pattern of the beam gets disturbed and the device takes it as an attempt of intrusion and then sends an alert signal to the Control Panel to act upon.

Advantages –

  • LASER based sensors are very much accurate in detecting the motion of objects.
  • These sensors are independent of light and hence provide ultimate detection in dark as well.
  • These sensors work well in all weather conditions be it rain, snow, storm, etc.

Applications –

  • Intrusion Detection System
  • Home Security System
  • Area Filteration

5. Dual Technology Motion Detectors

Many a Motion Detector is based on Dual Technolgy with the combination of PIR sensor and Microwave sensor to increase the efficiency of the whole Security System. Such dual technology motion detectors provide excellent detection and huge resistance to false alarms.


A motion detector senses movement within a specified area and converts this detection into an electrical signal to trigger various responses. Commonly used in security systems, automatic lighting, and home automation, these devices typically utilize technologies like Passive Infrared (PIR) sensors, ultrasonic sensors, microwave sensors, or dual-technology sensors. PIR sensors detect heat, ultrasonic sensors use sound waves, and microwave sensors use microwave pulses. Upon detecting motion, the sensor can activate alarms, lights, cameras, or other devices, enhancing security, energy efficiency, and automation in various settings.

The three main types of motion detectors are:

  1. Passive Infrared (PIR) Sensors: Detect infrared radiation emitted by warm objects, such as humans and animals, identifying changes in heat levels.
  2. Ultrasonic Sensors: Emit ultrasonic sound waves and measure the reflection off moving objects, detecting motion through obstacles and sensing even slight movements.
  3. Microwave Sensors: Emit microwave pulses and measure their reflection from moving objects, covering larger areas compared to PIR sensors.

These technologies are used to trigger alarms, lights, cameras, and other devices, enhancing security and automation.

Motion detectors themselves do not record; they detect movement and trigger an associated device to record. When integrated with a camera or a security system, the motion detector activates the recording device upon detecting motion. This setup ensures that recording occurs only when there is activity, conserving storage space and making it easier to review footage. Motion detectors paired with recording devices are commonly used in security systems, surveillance cameras, and smart home setups to enhance monitoring efficiency and security.

Scroll to Top