How does it work? | Rain sensor

Car rain sensor is an optic-electronic device, which is installed on car windshield and responds to hydration. It is necessary for the determination of moisture and automatically turn on the wipers. The first experiments to create rain sensor was carried out in 50-ies of the last century by automaker General Motors for Сadillac Eldorado. However, the imperfection of the technology of the time did not allow to bring the idea to life. One of the first production cars with the rain sensor became Nissan Silvia 94 model year. In the beginning the sensors were installed on vehicles from Volkswagen, BMW, Cadillac and others. Today, automakers are beginning to use rain sensors in standard cars and medium-class Golf. How do you operate the rain sensors — this is in the news today!

The rain sensor is a infrared emitter and a small photodetector, which in fact does not respond to moisture and light. Between the sensor and the windscreen is an optical element. His task is to focus and align the outgoing and incoming light. The sensor attached to the windscreen with adhesive foil. The principle of operation of the rain sensor is as follows: outgoing infra-red beams partly reflected on the surface of the glass, and then focused by the optical element and fall on the photodiode. The system is designed so that if the glass is dry, all the light is reflected back and fall on the photodetector. Since the beam is modulated by pulses, extraneous light sensor does not respond.

And the drops of rain or dirt located on the windshield, cause a change of the path refraction. And thus the amount of light hitting the photodiode changes. The stronger the wetting of the windscreen, the less the reflection of refracted light. On this information and based the sensor. The amount of reflected light recorded by the sensor, and the controller calculates a suitable mode of operation of the wiper. The sensitivity of the light receivers have been very high. They take into account a few thousandths of a milliliter of water on the windshield and actuate within a few milliseconds.

Some rain sensors have a sensitivity adjustment. It can be used to set the operation mode of the wipers: they will start working or in contact with the first drops, or when the rain really played out. There are models of sensors, which are able to control windshield washer.

It should be noted that as the work of the rain sensor based on the principle of reflection of infrared rays, it is able to operate at any time of day, including night. In winter, the sensor is a somewhat complicated, but when you turn on the defogger and the snow melting, it functions the same way as in the warm season in the rain.

How does it work? | Rain sensor
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