Rain sensor/light sensor, function - GF54.21-P-4123-04Q
Presentation of function overview of rain/light sensor
Function principle
Function requirements:
- Circuit 15R ON
Function principle
Infrared light is radiated from the IR transmitter unit (2) and guided to the windshield (4) via the lens (1). The intensity of the light reflected at the windshield (4) is measured by the IR-receiver unit (3) which is located at the other end of the lens (1)
- The windshield (4) is dry (Fig 1)
If the windshield is dry in the area of the rain/light sensor, the light is almost completely reflected: the IR receiver unit (3) measures a high light intensity.
- Windshield (4) is wet (Fig 1)
If there is moisture on the windshield (4) in the area of the reflection surface, part of the light is diffused from the glass on to the windshield (4). As a result the intensity of the reflected light reduces: the IR receiver unit (3) measures a lower light intensity.
The light intensity measured by the IR receiver (3) is a measure for the quantity of water on the windshield (4) The smaller the measured intensity the larger the quantity of water on the windshield (4).
Reading out via the rain/light sensor
The rain/light is connected with the interior CAN via the overhead control panel control module as interface
The front SAM control module with fuse and relay module (model 209) or driver-side SAM control module with fuse and relay module (model 211) or left front SAM control module (models 215, 220) transmits a request to the rain/light sensor via the interior CAN, this then conveys the instantaneous degree of wetting for each request.
The automatic driving light actuation actuates the low beam in the following cases:
- Dusk
- Darkness
- Driving through tunnels
and in the case of a detected sensor failure.
The above-mentioned switch-on conditions are considered separately and the driving lights are switched on when at least one of the conditions is met.
A detection of fog is not recognized. In fog the driving lights must continue to be switched on manually
Measurement and compensation
Via the serial interface the rain/light sensor receives information as to which wiper system it should actuate (reversing wiper system or two-stage), or whether the driving light should be switched on and emits the signals necessary for actuation