How does the sensor light detect the presence of people?

There are many different types of sensor lights on the market, and the following kinds of induction lights are the most common: sound-light controlled induction lights, human infrared induction lights, radar induction lights.

The infrared human body Sensor Light can turn on the lamp without making any noise. It is mainly composed of a pyroelectric sensor with a garfinier lens and a peripheral control circuit.

Pyroelectric sensors detect the radiation emitted by a person's body temperature, while Fenier lenses collect and focus infrared light emitted by the body.

When someone appears in the induction range, the Finier lens focuses the infrared radiation released by human heat onto the pyroelectric sensor, and then the pyroelectric sensor outputs a control model to the back circuit to realize the light on and off control.

Working principle
Objects with different temperatures will emit thermal radiation to the outside world, and the wavelengths radiated by objects with different temperatures are different. Human body has a constant body temperature, so a specific length of infrared radiation will be radiated. PIR human infrared sensor can receive and sense this wavelength, leading to current changes and triggering alarms.

Infrared pyroelectric body sensor works by detecting infrared radiation emitted by human body.
The main principle is: infrared radiation emitted by the human body about 10μm is enhanced by the Fresnel lens and concentrated on the pyroelectric component PIR(passive infrared) detector.

When people are active, the emission position of infrared radiation will change, the element will lose the charge balance, pyroelectric effect will occur to release charges to the outside, the infrared sensor will change the infrared radiation energy through the Fresnel lens into electrical signals, namely thermoelectric conversion.