Rain Sensor: Description and Operation

GF54.21-P-6000MCC Rain/Light Sensor, Component Description
- MODEL 451.3 /4 with CODE (V54) Rain/light sensor







B38 Rain sensor/light sensor

Location
The rain/light sensor is located on the inside of the windshield below the inside rearview mirror.

Task
To measure the light intensity and degree of wetting of the windshield







Function principle of rain sensor
1 Infrared transmitter unit
2 Infrared receiver unit
3 Windshield

Infrared light is radiated from the infrared transmitter unit and led to the windshield. The intensity of the light reflected at the windshield is measured by the infrared receiver unit If the windshield is dry in the area of the rain/light sensor (picture A), then the light is reflected almost completely and the infrared receiver unit measures a high light intensity If the windshield is wetted in the area of the rain/light sensor (picture B), then part of the light is scattered from the windshield glass. As a result the intensity of the reflected light reduces and the infrared receiver unit measures a lower light intensity.
The light intensity measured by the infrared receiver unit represents a measure for the degree of wetting of the windshield. The smaller the measured light intensity the greater the degree of wetting of the windshield.

Function principle of light sensor
The light sensor measures the light intensity striking it from outside. The resistance in the light sensor drops as the light intensity reduces.

The information from the rain/light sensor is passed on to the SAM control unit (N10/10) via the local interconnect network interior 1 (LIN B).