Infrared SensorsApplication Guide

Pyroelectric infrared sensors

There are many cases where infrared sensors are used for the purpose of detecting people.
Infrared sensors include active types which use light and passive types which detect heat (infrared rays). Murata's infrared sensors are called "pyroelectric infrared sensors," and they are passive sensors which use the pyroelectric effect in which a charge occurs when the heat of a piezoelectric element is detected. (Check the Basics for more details) The detection area and usage differ between optical and pyroelectric sensors, so they are used in locations according to each of their characteristics.

For example, let us use a toilet as an example.
The electricity turned on when you entered the toilet: pyroelectric infrared sensors
The toilet seat raises, water flows, water comes out when washing your hands: optical infrared sensors

As we can see in the toilet example, pyroelectric sensors are frequently used to detect when a person approaches a comparatively spacious area and you wish to trigger the next action, and optical sensors are often used when you wish to detect a person at a close distance.

Pyroelectric infrared sensors have a long history of adoption in crime prevention applications, and crime prevention systems from security manufacturers naturally use such sensors in IP cameras and various other crime prevention devices.
Usage examples in which a person is detected and lighting turns on have become quite common in doorbells, entryways, and parking lots, etc. With the advance of IoT in recent years, infrared sensors have also been adopted for use in smart homes and thermostats to detect people and automatically control air conditioning or turn home appliance products on and off.
Many thermostats and smart home control sections are battery driven, and there is a need to suppress power consumption. Pyroelectric infrared sensors, which detect the heat from people and generate a charge, do not run continuously like active type sensors, so they can be used for long periods of time with low power consumption, and because they can detect people across a wide area depending on the lens specification, they are increasingly being adopted for use in these applications.
In recent years, pyroelectric infrared sensors have also been utilized to detect and trap animals that destroy crops as well as search for valued pets.

Application examples in security

Application examples:

  • Battery-driven human presence sensors for IoT smart homes
  • IP cameras
  • Alarm systems and other crime prevention devices

Applications in the security field include not only checking the identification of visitors through doorbells and door cameras but also intrusion detection embedded in crime prevention devices such as alarm systems for homes, offices, and shops and the detection of suspicious persons and human movement in residences through thermostats and other IoT smart home devices and IP cameras.

Wake up utilization examples

Application examples:

  • Digital signage and vending machines
  • Air conditioners, air purifiers and other general appliances
  • Printers (MFP), meeting displays, PCs and other OA equipment

The wake up feature is utilized not only in household appliances but also printers, PCs, and other office products with a long standby time until start up as well as digital signage, vending machines, and other equipment which operates when a person approaches.