Radar induction: Using Doppler radar induction principle, by transmitting 5.8GHz radar signal, once a moving object enters the sensing range, the radar signal waveform will be changed, thus triggering the action of the radar sensor. It is not affected by the ambient temperature and sound loudness. It is the most humanized induction technology; human body induction: using pyroelectric infrared induction principle, through collecting infrared The energy change triggers the action of the sensor, which is affected by the ambient temperature. When the ambient temperature is close to the body temperature in summer, there is no change in infrared energy when people enter the sensing range. Therefore, the human body's sensing performance is very insensitive in summer.

1. Working principle of radar induction

The radar induction module is composed of microwave oscillator, amplification and shaping circuit and detection circuit. When working, the microwave oscillator emits ultra-high frequency (GHz) electromagnetic wave through the antenna printed on the PCB board, according to the principle of microwave Doppler.

If there is a moving object around the radar module, its antenna will receive the electromagnetic wave reflected from the moving object. There is a certain frequency difference between the frequency of the reflected electromagnetic wave and the frequency of the electromagnetic wave emitted from the module. After the frequency difference is amplified and shaped by the receiving circuit, a control signal can be output to control the load.

2. Working principle of human body induction

Human body sensing module. It is composed of Fresnel lens, pyroelectric sensor and induction signal processing circuit. Because of the infrared filter in front of the pyroelectric sensor used in this module, it can only detect the infrared signal with a wavelength of more than 10 um from human body. The Fresnel lens equipped with the module is used to improve the sensitivity.

When the module works, as long as someone moves around in the monitoring area of pyroelectric sensor, the sensor will output corresponding electrical signal, which is processed by the induction signal processing circuit and outputs a control signal to control the work of the load.

The two induction modules mentioned above can be used for the control of induction lamp and automatic door. The advantage of using microwave induction module is that it has no direction. As long as someone or other objects move in the monitoring area of the module, the control can be realized. Its disadvantage is that the power consumption of the module is large (the working current is at Ma level), and the price of this radar induction module is several times higher than that of the pyroelectric human body induction module.