What is the Principle of Rain-Sensing Wipers?

[AliyahLynn]

Currently, the two most widely used mainstream sensors for automatic rain-sensing wipers are optical sensors and capacitive sensors. The differences between optical sensors and capacitive sensors are as follows: 1. Optical Sensor: It operates based on the principle of light refraction. An optical sensor contains a light-emitting diode (LED) that emits a conical beam of light, which passes through the windshield. When the windshield is dry and free of rain, almost all the light is reflected onto an optical sensor. When it rains, water droplets on the windshield cause some of the light to scatter, resulting in a change in the total amount of light received by the sensor. This allows the sensor to detect the presence of rain. 2. Capacitive Sensor: This type of sensor is primarily designed by leveraging the significant difference in dielectric constants between water and glass, where water has a dielectric constant of 80 and glass has a dielectric constant of 2. When the windshield becomes wet, the dielectric constant of the windshield changes depending on the amount of water in contact with it.