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Human body induction related sensor application scheme

Apr 17,2023

Industry background:

A human body induction sensor, also called a PIR sensor, is a sensor that can detect infrared rays emitted by people or animals and output electrical signals. As early as 1938, it was proposed to use the pyroelectric effect to detect infrared radiation, but it was not taken seriously. It was not until the 1960s that the research on the pyroelectric effect and the application of the pyroelectric crystal emerged.

Objects existing in nature, such as the human body, flames, ice cubes, etc., all emit infrared rays, but their wavelengths are different. The human body temperature is 36-37°C, and the emitted infrared wavelength is 9-10um, which belongs to the far infrared region. PIR sensors are not affected by day or night and can be used for monitoring around the clock.

Advantages and disadvantages of passive PIR probes:

Advantage:

It does not emit any type of radiation itself, the power consumption of the device is small, and the concealment is good. Inexpensive.

Shortcoming:

◆Easy to be interfered with by various heat sources and light sources

◆Passive infrared penetration is poor, and the infrared radiation of the human body is easily blocked and difficult to be received by the probe.

◆Susceptible to interference from radio frequency radiation.

◆When the ambient temperature is close to the human body temperature, the detection and sensitivity will drop obviously, sometimes resulting in short-term failure.

Anti-interference performance:

1. Anti-interference of small animals

The detector is installed at the recommended operating height, and generally does not generate an alarm for small animals on the ground within the detection range.

2. Anti-electromagnetic interference

The anti-electromagnetic wave interference performance of the detector meets the requirements of 4.6.1 in GB10408, and the electromagnetic interference of general mobile phones will not cause false alarms.

3. Anti-light interference

In the range of normal sensitivity, the detector will not generate an alarm when it is irradiated by the H4 halogen lamp 3 meters away through the glass.

Application occasions and detection gas types:

Based on the low cost characteristics of pyroelectric sensors, they were widely used in the field of induction lights in the early stage of market application. The common ones are corridor induction lights, which turn on when people come and go. With the development of some home appliance brands such as Xiaomi, Haier, Midea, etc., smart home appliances are increasingly accepted by more consumers, and the function of human body sensing is "humanized", which fits well with the concept of smart home appliances. , In recent years, it has been more and more applied to traditional home appliances. Today's smart home appliances are a combination of traditional home appliances + sensors + cloud platforms. Sensors are the "nervous system" that allows traditional home appliances to perceive, and the cloud platform is equivalent to the "brain", allowing people and home appliances to understand each other.

Here are some scenarios for the application of PIR sensors:

1. Wardrobe sensor light: RD-624 pyroelectric infrared sensor

Wardrobe sensor light