Rain/Light Solar Sensor
Rain/Light Solar Sensor
Rain/light solar sensor
The rain/light solar sensor groups the following sensors and components into one control unit:
- Rain sensor: consisting of 3 individual sensors arranged in a semicircle around the driving light sensor, picking up the precipitation quantity on the windscreen.
- Driving light sensor: consisting of 2 photosensors that pick up the brightness of the ambient light and of the frontal light. On the E70, the front light sensor regulates the brightness of the Head-Up Display.
- Solar sensor: It consists of 2 photosensors that measure the intensity of the sunlight for the driver's and front passenger sides.
- Electronic component: It evaluates the sensor signals.
Requirements for trouble-free operation of the rain sensor are:
- Wiper blades OK
- No streaking on the windscreen
- Sensor area free of dirt contamination (road salt, insects)
- Windscreen in the area of the rain sensor without faults (stone chipping)
- Optical element bonded free of bubbles with the windscreen glass
Brief component description
The rain/light solar sensor is inserted from the inside of the windscreen in the wiper range of the windscreen wiper.
The rain/light solar sensor is fixed in the bracket by a steel-plate spring. The bracket is firmly bonded to the windscreen. There is a gel pad between the rain/light solar sensor and the windscreen. The gel pad is fitted on the optical element (new part). The silicone gel provides the optical connection to the windscreen and prevents dirt from entering. Important: After installation of a new rain/light solar sensor, the gel pad can no longer be removed without damage, rather the gel is destroyed.
This installation location ensures that the windscreen surface in the area of the sensor remains free of dirt and ice.
To prevent the sensor surface from fogging over, the sensor is heated.
The rain/light solar sensor is supplied with voltage from the roof function centre. The signals of the rain/light solar sensor are transferred through the data buses.
Rain sensor
The rain sensor is an optical sensor and consists of an optical element. An electronic component is also integrated. Alongside the evaluation electronics, 3 optical transmitter and receiver diodes are integrated in the electronic component.
Driving light sensor
The driving light sensor is also an optical sensor and consists of 2 photo diodes and the corresponding electronic evaluation unit. One photosensor is aligned forwards and it picks up the light that strikes the front (frontal light). The second diode is aligned upwards and it picks up the light striking from above (ambient brightness).
Solar sensor
The solar sensor consists of two photosensors. These diodes are fitted on the right and left on the sensor field of the rain/light solar sensor.
Electronic component
The electronic component evaluates the individual sensor signals and communicates with the roof function centre (FZD).
System functions
The following system functions are described for the rain/light solar sensor:
- Detection of precipitation
- Detection for driving lights
- Detection of the sunlight intensity
Detection of precipitation
Pressing the button on the wash/wipe switch activates the rain sensor. When the rain sensor is active, the function LED on the wash/wipe switch lights up in green.
First of all, one wipe cycle is run as visual acknowledgement of the switching on. Then, the 3 transmit diodes emit infrared light that is routed via the optical element to the windscreen. If the windscreen is completely dry and clean, the infrared light is fully reflected to the 3 receiver diodes.
If there is water or dirt in the area of the optical element on the windscreen, the infrared light is refracted. This means that only part of the infrared light is reflected to the receiver diodes. The reflected light quantity is thus the measurement of the intensity of the precipitation in the area of the optical element. On the basis of the missing quantity of light, the evaluation electronics detect the degree of wetness on the windscreen glass and transmit a signal via the bus. On the basis of this signal, the junction box electronics (JBE) evaluates whether a wipe cycle is necessary.
The sensitivity of the rain sensor can be varied in 4 sensitivity stages by means of a knurled wheel on the wash/wipe switch. Each operation of the knurled wheel towards "Increase sensitivity" (i.e. turning the knurled wheel upwards) runs a wipe cycle.
With the vehicle stationary and failure of the rain/light solar sensor, the windscreen wiper is switched into a fixed intermittent operation mode. On switching off terminal R, the rain sensor is switched off for safety reasons.
As of 09/2011, the protection function "Ice detection" will be introduced. At outside temperatures of below 0 °C (observe outside temperature display in the instrument panel) and with the rain sensor activated, automatic wiper operation is not possible. The following functions are suppressed:
- Single wipe if automatic wiper operation is activated
- The other wiper cycles if the windscreen is wet
As a result of the suppressed functions, possible damage to the windscreen wiper, for example due to frozen wiper blades, is avoided.
When a speed of 7 km/h is exceeded after the engine start for the first time, the protection function "Ice detection" switches off automatically. As of this time, automatic wiper operation is possible once again without restriction until the next time the engine is switched off and the vehicle enters the sleep mode.
Manual wiper operation is not affected by the protection function "Ice detection". That means: wiper stage 1 and wiper stage 2 can always be set manually.
Detection for driving lights
The change in lighting conditions in front of the vehicle and in the surrounding area of the vehicle is picked up by the light-sensitive sensors. The lighting condition is processed by the evaluation electronics and sent via the data bus to the footwell module. Depending on the brightness, with the automatic driving lights control active, the driving light is switched on and off.
Detection of the sunlight intensity
The solar sensors measure the intensity of the sunlight separately for the driver's and front passenger side. The sensor data is processed in the evaluation electronics and transmitted via the bus to the IHKA control unit. The IHKA control unit evaluates these sensor signals.
Notes for Service department
The following information is provided for service of the rain/light solar sensor:
General notes
A dry and undamaged windscreen surface is necessary for installation of the rain/light solar sensor. The sensor must always be cemented to the windscreen without any trapped bubbles. For trouble-free operation of the rain/light solar sensor, there must be no streaks on the windscreen. Moreover, the wiper blades must be OK.
Diagnosis instructions
Initialization of the rain sensor
To ensure that the optical measuring procedure for the detection of precipitation functions properly, the rain sensor must be adapted to the windscreen.
A prerequisite for trouble-free initialization is that the windscreen glass is dry, clean and free of defects in the area of the rain sensor.
The initialization is performed using the "Initialize rain sensor" service function in the diagnosis system. The adaptation values stored in the rain sensor are deleted in this service function.
A re-initialization of the rain sensor is required:
- After replacing the windscreen
- After installation of a rain/light solar sensor
Encoding the rain/light solar sensor
Encoding of the rain/driving light solar sensor is required:
- After replacement of the windscreen, if replacement of the rain-light-solar-condensation sensor is required
- After replacement of a rain/light solar sensor
The automatic driving lights control provides an encoding possibility to change the sensitivity settings (Japanese version: changed sensitivity settings).
Restrictions due to factors inherent in the system
Rain sensor:
Dirt contamination of the sensor surface can lead to unwanted activation, up to and including continuous wiping. If the dirt contamination continues over a longer period, the system reacts with a reduction in sensitivity.
Dirt contamination can be caused by road salt residue, insects or streaks. The windscreen should therefore be cleaned from time to time using the wipe-wash function.
As the wiper cleans the sensor surface, the wiper must not be worn. A worn wiper would diminish the measured values of the sensor by streaking as the values are no longer able to change.
Formation of bubbles/blisters on the bonding surface of the optical element also leads to impairment.
Light sensor:
Due to the high ambient brightness, fog cannot be detected by the light sensor.
The light sensor is sensitive to light in the infrared range. The infrared proportion is high if there is dense cloud cover. With lighter cloud cover or blue sky - above all in winter - the sensor receives considerably fewer infrared light proportions. This means the light sensor switches the light on earlier or leaves it on for longer.
In well illuminated tunnel entrances, startup can be delayed. The high level of lighting means that the measured values are above the switch-on threshold.
The formation of bubbles/blisters on the bonding surface of the optical element impairs the lighting function We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.