GF54.30-P-2007SX Instrument Cluster Illumination, Function
GF54.30-P-2007SX Instrument Cluster Illumination, Function
Component Identification:
Activate
The instrument cluster illumination switches on automatically as soon as the instrument cluster is activated. The details of the Instrument cluster are only now clearly visible on account of the "Black-Screen Technology".
Illumination
The instrument cluster illumination depends on the following factors:
^ Light falling directly on the instrument cluster (measured by the left brightness sensor and right brightness sensor.)
^ Detected light intensity outside the vehicle (measured by the rain/light sensor (day/night signal).
^ Adjustment of switch and controls illumination/Night View Assist display brightness control
Day/night signal
The rain/light sensor measures the light intensity outside the vehicle, converts this into electrical signals and passes on the signals to the overhead control panel control unit. The overhead control panel control unit evaluates the signals and places the day or night signal on the interior CAN. The central gateway control unit (N93) reads in the signal from the interior CAN and places it on the central CAN. The instrument cluster reads in the signal from the central CAN and actuates the brightness of the instrument illumination and multifunction display accordingly. For the day signal the instrument cluster is illuminated more brightly than for the night signal.
In addition to a limited extent the brightness of the instrument illumination and multifunction display can be readjusted individually via the switch and controls illumination/Night View Assist display brightness control in the cockpit switch group.
Direct solar radiation on the instrument cluster
The left brightness sensor and right brightness sensor are integrated in the instrument cluster. These brightness sensors measure the light falling on the Instrument cluster. If, for example, the sun shines directly on the instrument cluster, the brightness of the instrument illumination and multifunction display is increased accordingly, in order to achieve ideal legibility of the displays.
In addition to a limited extent the brightness of the instrument illumination and multifunction display can be readjusted individually via the switch and controls illumination/Night View Assist display brightness control in the cockpit switch group.
circuit 58d on/off ratio
The lamps of the switch and controls illumination are actuated with a square-wave voltage.
The lamps are actuated in the on-time, afterwards followed by a break until the end of the period. This process is continuously repeated. The change happens so quickly that the eye does not notice the lamps flickering. The ratio of the on-time to the cycle duration is called the duty cycle. In the process the cycle duration is constant and the on-time is the time in which voltage is applied within a period. The greater the duty cycle, the greater the average consumed power and thus the brightness of the lamps. The curve of square-wave voltage as it applies at the outputs "circuit 58d" of the various control units is drawn in the figure. The upper drawing in the figure shows a duty cycle of 80 %, the lower a duty cycle of 40 %. A pulse-duty factor of 100 % corresponds to DC power. Power is not supplied when the duty cycle is 0 %.
Switch and controls illumination
The brightness of the switch and controls illumination can be adjusted with the factors listed. Control takes place via the duty cycle of "circuit 58d". The duty cycle of "circuit 58d" is placed on the Controller Area Network (data bus/CAN bus) (CAN) by the instrument cluster and can thus be received by any control unit connected to the CAN. Any control unit, which regulates a switch and controls illumination, can now actuate this independently based on the duty cycle.
Advantages of this type of brightness control:
^ The brightness of the switch and controls illumination is independent of the number of lamps or control units fitted.
^ Each control unit, which is connected to the CAN, can actuate its lamps with the brightness specified by the instrument cluster.
With "circuit 58d OFF" (standing lamp OFF) the instrument cluster transmits the message "duty cycle circuit 58d = 0 %".
With "Tml. 58d ON" (standing lamps ON), the transmitted duty cycle can vary from 0 % to 100 % depending on the setting.
