What is PIR Motion Detector

What is PIR Motion Detector
What is PIR Motion Detector

PIR sensor is a device that detects movement by receiving infrared radiation. It detects a rapid change in infrared energy and emits a signal when there’s somebody going by the sensor. In this article, we will demonstrate the difference between PIR and IR sensor, the difference between PIR sensor and motion sensor, and also what is PIR motion detector.

The distinction between PIR and IR sensor

Do you know the distinction between a PIR sensor and an IR sensor? Next, we’ll tell you the difference between a passive infrared sensor and an infrared sensor. Some IR sensors are used in daily life, such as infrared remote control to change TV channels and security sensors that detect movement through infrared radiation, including automatic garage doors. In a standard infrared sensor, the transmitter emits invisible light to a receiver some distance away. If the receiver doesn’t receive the signal, the sensor knows that something is within its range.

  • PIR, short for Passive Infrared Sensor, uses Infrared technology to memorize the Infrared image of the surrounding area and if there are any changes caused by movement, it will notice.
  • Infrared sensor is a kind of infrared sensor, that can use an infrared technology chip and emitter to determine whether the light emitted by the emitter is from objects or people.
    The main differences include:
  • The light emitted by the transmitter that infrared sensor detected is from objects or people. However, PIR sensor obtained the judgment by detecting the variation of the energy level around the zone.
  • If a PIR sensor is installed in a changing environment, it can automatically make false judgments due to changes in the way air flows. However, infrared sensors must be mounted towards motions.
  • A infrared sensor is typically installed on the outside of the property, while a PIR sensor is installed on the inside of the device.
  • Unlike infrared sensors that emit infrared, PIR sensors don’t actually emit infrared, it’s objects that emit infrared to the sensor.

Distinction between PIR sensor and motion sensor

Motion sensors detect the movement of objects and people. In most applications, they are primarily used to detect human activity in specific areas. It can also converts movement into electrical signals. Sensors either emit stimuli and track any changes reflected back, or pick up signals from the moving object. alarms and/or automatic lighting switches is triggered by motion sensors in most of the security systems around the world. More often, they are placed in easy access to buildings, such as gates and windows.

PIR is just one of the technical ways to detect motion, so we say that PIR sensors are a subset of motion sensors and PIR sensors are small, cheap, low power consumption, very easy to understand, which makes it very popular and many businesses will add motion sensors between PIR sensors.

The function of PIR sensor



The function of PIR sensor

First, we need to know that all things, including humans, animals, and even inanimate objects emit a certain amount of infrared radiation. The amount of infrared radiation is related to the temperature and material composition of the human body or object. Although humans can’t see infrared, we have designed electronic detection devices, which can detect infrared. You can see PIR sensors are used for thermal sensing such as security and motion detection.

Motion sensor

A motion sensor, or motion detector, can detect people or objects nearby. Motion detectors, like door and window sensors, are an important part of home security systems. Though there are several different types of motion detectors on the market, most of them rely on similar technology to detect intruders. They can detect small changes in the space they cover, such as temperature, vibration or radiation. An alert will be sent to your security system when the sensor detects your movements.
Motion sensors are commonly used for:

  • Detect when a potential intruder approaches or is in your home or business
  • Notify you if anyone enters restricted areas like your garage,basement or warehouse
  • Save energy by lighting an area only when it’s required

Two widely used motion sensors

Active ultrasonic sensor and passive infrared sensor are two of the most commonly used motion sensor technologies, accuracy and reliability are their advantages.

Active ultrasonic motion sensor

Active ultrasonic motion sensors emit ultrasonic waves at frequencies above the range of human hearing that are reflected back from nearby objects and then returned to the movement sensor. The transducer in the sensor serves as the waypoint of the signal, which sends pulses and receives echoes. The distance depends on movement sensor. You can configure sensitivity in motion sensors so that it won’t trigger if the object distance is too far. If the received signal is within the specified parameter range, the motion sensor will trigger, alerting you that there is someone or something near the sensor. Motion sensors installed at entry points (such as Windows and doors) can be configured to trigger burglar alarms Window and door sensors are designed to detect someone who intrudes, in this way you needn’t deal with excessive notifications or false alarms. Ultrasonic sensors can detect surface type, object color, or material type and they can even detect translucent objects, although this is usually only used for industrial occasions.

Active ultrasonic motion sensor

Passive infrared motion sensor

PIR motion detector come in two types:

  • Thermal infrared sensors: Thermal infrared sensors or pyroelectric infrared sensors use infrared as a heat source to detect objects. Their sensitivity is independent of wavelength. Detection time and response speed is slow.
  • Quantum infrared sensors: Quantum sensors detect photons, depending on wave length, and are more sensitive than those that sense heat. These sensors are fast in detection and response, while requiring frequent cooling to make accurate measurements.

Everything above absolute zero emits infrared radiation around it. PIR sensor is a thermal infrared sensor that detects the movement of objects by reading the changes of infrared radiation in the surrounding environment. When the sensor is inactive, both slots can sense the same amount of IR from any object. When a warm object comes within range of the PIR motion detector, it passes through the two slots, one after the other. When it intercepts the first half of the sensor, there will be a positive differential change between the two halves and similarly, when it leaves the detection region, there will be a negative differential change between the two slots and these changes in the pulse are an indication to the sensor that there is some movement in its detection region.

Walls, floors, stairs, Windows, cars, dogs, trees, and all other things you can think of all emit a certain amount of heat. by detecting temperature changes in a given area, infrared motion sensors can detect the presence of people or objects Let’s use a motion sensor to illustrate the working principle.

There are two sensors in the PIR sensor. When there’s no one nearby, the PIR sensor detects ambient infrared radiation from background objects, such as walls and doors. When a person (or animal object, etc.) passes by the sensor, the first sensor intercepts their heat signature and the sensor kicks in, alarm is triggered and you will be alerted. If the object happens to be out of range of the sensor, a second sensor activates, recording a sudden drop in temperature. The presence of people or objects will be detected by the PIR motion detector, which detect based on the temperature changes. PIR sensors can be set to ignore tiny changes in infrared, so alarm will not be triggered when you’re walking around your home or business.

Passive infrared motion sensor

Strength and drawback of PIR motion detector

Strength of PIR motion detector

The PIR motion detector can detect movement in the dark with high precision. PIR sensors can detect the movement of objects without touching them and they’re very easy to install, they don’t require a lot of wiring and they save a lot of workforce by making things work automatically and they consume very little energy,thus reducing electricity bills significantly.

Drawback of PIR motion detector

In bad weather conditions,PIR sensors may behave abnormally, sometimes fail to detect very slow-moving objects, and home security systems equipped with PIR motion detector sometimes trigger false alarms. Their detection range is not wide enough, and sometimes there are holes in the burglar alarm system due to inadequate coverage Of course, these are issues that can be solved, we’ll talk more below about how to effectively avoid these problems.

Tips for using PIR motion detector

Like security cameras, fire alarms and burglar alarms, installing PIR motion detector in the most important locations ensures that your home or business is secure. You can use an app to quickly access the entire security system from your phone. When you install the PIR motion detector, be sure to follow the instructions on the sensor. Here are some tips for installing motion sensors in your home or business:

1. Install door motion sensors near the entrance.

2. Put them in a heavy traffic area. If you put sensors in hallways or stairwells, or other places people have to walk through, you’re more likely to catch intruders. You’d better place sensors near to the rooms where you place your valuable items.

3. Do not install PIR motion detector near heat sources. PIR sensors analyse temperature fluctuations and false alarms can be triggered if they are installed too close to stoves, vents, or fireplaces.

4. Do not block the sensor. If blocked, the sensor will not work properly. Blocking may not be obvious at first. For example, your parked car might block it from detecting movement on the sidewalk or street if you install a motion-sensor light on the house above your driveway. Try to place the sensor in an area without contamination.

5. After installation, please wipe the sensor clean to ensure that the lens is unblocked and clean regularly.

6. You must don’t want your phone to be flooded with mobile notifications only to find that your pet is walking around the house. By configuring the detector’s notification Settings as per your needs, or use the default Settings,you can resolve this issue.

How’s the range of different PIR motion detector?

Indoor passive infrared: detection vary from 25 centimeter to 20 meters.
Indoor curtain type: detection range 25 centimeter to 20 meter.
Outdoor passive infrared: detection range of 10 m to 150 m.
Outdoor PI curtain detector: distance range from 10 m to 150 m

Application field of PIR motion detector

  • Burglar alarm system or intrusion detection system
  • Automatic household appliance
  • Automatic gate
  • Automatic lighting
  • Infrared thermometer
  • Night Vision Camera
  • Gas analyzer
  • Humidity analyzer
  • Smoke and fire detectors

Some PIR motion detector technology that are less commonly used

  • The tomographic motion sensor consists of multiple nodes connected together to form a mesh network. When the link between two nodes is out of connection, the presence of people or objects can be detected.
  • Vibratory motion sensors detect people and objects through small vibrations caused by such things as footsteps.
  • A microwave motion sensor emits microwave pulses that bounce off the object and return to the sensor. Compared to PIR sensors, a larger area can be covered, but they’re more susceptibility to electronic interference.


The setup of our PIR sensors is pretty simple while others in the market are full of features that you might spend a lot of time configuring. Choose what works best for you, or talk to a expert from MOKOLoRa to learn more about the operation. PIR motion detector is essential in security system, they are a good way to detect intruders and other suspicious activity. If you’re ready to increase the security of your businesses or home, send us an inquiry, we’ve been in this industry for over 16 years.

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