Pyroelectric infrared element is a photoelectric element whose input is infrared radiation. It is usually used to detect the infrared energy of human radiation, which triggers various automated systems and devices, such as automatic lighting, automatic door locks, and so on.

The core of the pyroelectric infrared element is a special material called pyroelectric material. The material is able to sense temperature changes in the surrounding environment and convert these changes into electrical signals. When infrared radiation hits a pyroelectric material, it absorbs this radiation and heats up, causing a change in the material's conductivity. This change can be converted into a voltage signal that triggers a subsequent circuit.

In order for a pyroelectric infrared element to work properly, it needs to be placed in an optical system in order to focus the infrared radiation onto the element. In addition, pyroelectric components require a filter to block interference from visible and other non-infrared light.

In short, the input of the pyroelectric infrared element is infrared radiation, and its working principle is based on the heat of the pyroelectric material