This smart device is located inside the machine – how does it feels raindrops? The key is that the rain sensor reacts not to moisture but to light. It has two elements: the LED and photo-diode The LED emits infrared light. We do not see the light, but actively use in everyday life – such as switching TV channels by remote control.
Infrared light strikes into the glass, it is partially reflected from a smooth surface and go back to the sensor. Then he is caught by a photo-diode It determines the amount of returned light. When the glass is dry, a lot of light returns. When it is wet – much less, as a drop of water through the light easily penetrates to the outside. Fixing that the glass is wet, the sensor activates the windshield wipers. Some sensor models can quite accurately determine the amount of moisture and, accordingly, to adjust the speed “janitors” and supply of washer fluid.
One of the first production cars with rain sensor is Nissan Silvia – a sports coupe. In the 2000s there were rain sensors on cars Volkswagen brands, Cadillac and other leading manufacturers.