What is the principle of rain-sensing wipers?

[DelJayden]

Here is how the rain-sensing wipers work in cars: When the sensor detects rain falling on the windshield, it sends a command to the wipers to start working, and the rainwater on the front windshield is cleared. Currently, the two widely used mainstream sensors are optical sensors and capacitive sensors. Below is a detailed introduction: 1. Optical sensor: In an optical sensor, there is a light-emitting diode that emits a conical beam of light, which passes through the front windshield. When the windshield is dry and free of rain, almost all the light is reflected to an optical sensor; when it rains, rainwater remains on the windshield, causing some of the light to deviate. This results in a change in the total amount of light received by the sensor, thereby detecting the presence of rain. The larger the area of reflected light that the optical sensor can receive, the more detailed the information obtained. Optical sensors are highly precise and can even accurately determine the number of raindrops falling on the sensing area. 2. Capacitive sensor: It is primarily designed based on the significant difference in dielectric constants between water and glass, where the dielectric constant of water is 80 and that of glass is 2.