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Infrared sensors for home security

The development of smart home, so that the gradual popularization of intelligent home network, as an extension of human five senses, more and more sensors are widely used in smart home devices. For example, gas sensors are used in home security equipment such as gas alarms and smoke alarms, and it can be said that the existence of security sensors is essential to ensure home safety.

At present, security sensors mainly include gas sensors, human body sensor sensors, smoke sensors, door sensor and other types. Today we talk about the most used passive infrared detector.

What is a passive infrared detector?
Passive infrared detectors rely on passive absorption of infrared heat energy emitted by the body when the human (or animal) activity is used to alarm.

According to scientists, any object with a temperature higher than absolute zero (-273 ° C) is always constantly radiating infrared rays to the outside world, and the spectrum of thermal radiation is mainly located in the infrared band.

The human body is also a source of infrared radiation, and the ability to radiate varies from person to person, and the radiation capacity of different parts of the human body is also different. The infrared peak wavelength of human radiation is about 10 μm, that is, we can detect the active human body as long as we capture the infrared radiation source with an infrared peak of 10 μm.

How does it detect infrared?
So how does the infrared detector detect the infrared rays of human radiation? There are 2 key elements in the passive infrared detector, one is a Fresnel lens and the other is a pyroelectric sensor.