At present, the most commonly used component in smart homes is probably the human body sensing sensor, but the human body sensor is also the most difficult component to arrange at present, which can easily be accidentally touched and affect the user experience if not paid attention to. This article takes you through the characteristics and layout methods of human body sensors.
The human body sensor only has one function - to sense the movement of the human body or pet. It is worth noting that it senses the movement of the human body and pets, rather than humans or pets, which is determined by the principle of the human body sensor itself. At present, the vast majority of human body sensors in the smart home market use infrared sensors with pyroelectric effects.
Due to temperature changes, pyroelectric crystals and piezoelectric ceramics may experience relative displacement of charge centers in their structures, resulting in changes in their spontaneous polarization intensity and the generation of heterologous bound charges at both ends. This phenomenon is called the pyroelectric effect.
Simply put, it is because the human body or animal body radiates infrared radiation related to its own temperature. When the emitted infrared radiation is irradiated on the pyroelectric material, the pyroelectric material will generate a signal of related potential changes. Based on this signal, it can be determined whether there is a human body or pet moving.
However, due to the extremely weak infrared emitted by the human body, most human body sensors will add a Fresnel lens that gathers the human body's infrared rays, achieving higher accuracy in human movement detection.
From a principle perspective, most of the currently used pyroelectric human body sensors can only recognize the movement of the human body, that is, the changes in infrared radiation emitted by the human body. If the human body is in a stationary state, pyroelectric sensors cannot distinguish whether there is someone present.
At the same time, because pyroelectric material identification is an infrared ray spontaneously generated by human body temperature, pets, cats, dogs and even radiator in the north that are similar to human body temperature may cause human body sensors to touch by mistake.
Improper placement of human body sensors can also lead to poor signal quality, as the infrared emitted by the human body can be attenuated by materials such as glass and curtains. Therefore, when placing human body sensors, we should pay special attention not to point the side with the lens towards materials such as glass to avoid being obstructed. At the same time, do not install the human body sensor directly in the wiring box, otherwise it will affect the recognition range of the sensor.
The following points should be noted when installing a human body sensor:
1. The recommended installation height is between 1.2 meters and 2.1 meters, as below 1.2 meters will reduce the detection range, while above 2.1 meters, there will be an undetectable "blind spot" at the bottom of the sensor.
2. If there are cats, dogs, and other pets at home (similar to humans) with constant temperature, it is recommended to install the human body sensor upside down and lower the installation height to prevent accidental contact by pets when moving on the ground. Although this will reduce the triggering range of the sensor, it can effectively avoid pet accidental contact.
3. To avoid materials such as glass within the detection range that weaken the transmission of human infrared rays, it is best to install a human body sensor on the side of the door to detect the entrance and exit of the door. At the same time, the detection surface of the sensor is perpendicular to the door, detecting the human body relatively close to the door, in order to improve the accuracy of the detection.
4. Within the detection range of human body sensor, it is better not to have radiator, electric heater, incandescent lamp and other things that may be close to human body temperature to avoid accidental contact of human body sensor.
5. Multiple human body sensors can be used together. If a single human body sensor cannot detect the entire aspect, multiple sensors can be set up for joint use to improve the detection range. Multiple human body sensors can also be arranged in small spaces to improve detection accuracy.
For current human body sensors, it is difficult to install them accurately in one go. Therefore, in daily use, the angle and orientation of the human body sensor can be adjusted according to your own needs to improve the effectiveness of the human body sensor.