Rain sensor

The rain sensor is a device responsive to water and dirt on the windshield. Electronic controls automatically adjusts wiper speed and wiper rain intensity of the incident. The system features its automatic control of the vehicle increases comfort.

Cars equipped with rain-sensing wipers operate automatically without any intervention by the driver. Rain sensor electronics can adapt to the speed of the wiper current conditions.

Principle:

In the middle of the rain sensor is located and the sensing diode is positioned around the perimeter of several radiating diodes. Emitting diodes are divided into two groups. These two groups alternately emit infrared radiation, the reflection from the windscreen is capturing sensing diode.

The sensing diode in the middle of the rain sensor turns the reflected rays fall on one side and the second group of radiating diodes. If the rays fall with the same intensity from both groups, there is no diode to capture any tension. This state corresponds to a dry windshield.

In the case of wet windshield conditions are reflection and transmission of infrared rays others. One part of the transmitted beam is reflected back from the glass, while the latter passes through the glass. The sensing diode then turns out to be weaker radiation intensity. The sensing diode voltage signal arises. This situation corresponds to polluted windshield.

Physical basis:

Rain sensor uses a physical law of refraction waves in the optical transition from one environment to another. Under certain conditions, there is total reflection (total reflection), ie. the waves from one medium to another does not penetrate at all. If there is a reflection or refraction depends on the angle of incidence of infrared rays. Incidence angle "alpha" is the limit angle of total reflection. If the outside of the windshield violated the conditions of refraction, and occurs when the condition of total reflection to refraction. That is when they are on the windshield as rain. The condition of total reflection becomes part of a wave penetrates the glass.

History:

When cars first appeared in the rain wipers were still on hand drive. They were small and poorly wiped dirt. Later wipers were powered by compressed air and electric motors. These bikes were initially a fixed speed wiper and it was clear that the heavy rain will sweep poorly, or vice versa in light rain will scrub almost dry glass. Therefore, it soon appeared windscreen wipers or even multi-speed with variable speed wiper (intermittent). The last stage of development are equipped with automatic rain-sensing wipers.