Panel Illumination Control Module: Description and Operation

GF54.30-P-3008A Instrument/Display Illumination, Location/Task/Function







Instrument illumination
The brightness of the instrument illumination can be adjusted with the adjusting button (b) on the instrument cluster (A1).

The dimmer circuit drawn in the illustration is used for this. It is supplied from terminal 58k and supplies a square-wave voltage to terminal 58d, whereby the on/off ratio of around 12 - 100 % is adjustable.

The frequency of this voltage is approx. 64 Hz. Terminal 58d goes directly to the instrument illumination lamps and is available for external consumers up to a power of approx. 23 - 30 watts (depending on the model). Terminal 58d is short-circuit proof. The output voltage corresponds to battery voltage minus 0.5 V. On models 202,208 and 210 the on/off ratio depends on the brightness of the surroundings which is measured by the phototransistor (pt). The instrument cluster transmits the on/off ratio as a CAN message. The information from terminal 58d is consequently available to all CAN participants.

On/off ratio
The ratio of the times t1 to T is called the on/off ratio. T is the period and t1 in which current can flow within a period.

The greater the on/off ratio, the greater is the average power (brightness of the lamps) which is delivered to the consumers (I). The voltage curve at terminal 58d is sketched for an on/off ratio of 40% and, for comparison, 90% in the figure.

The advantage of this type of brightness control compared with direct control of the lamp current with a potentiometer is the significantly higher efficiency, the extensive independence of load and the more compact construction.

Display illumination (models 129, 140 up to 05.97 and 163, 168)
The display illumination has an actuated daytime/nighttime switchover via terminal 58k.

When the vehicle lights are switched off (daytime) the display illumination is switched to maximum brightness (to 88% on model 163). When the vehicle lights are switched on (night-driving or day-driving light) the display illumination is dimmed.

The displays can be dimmed together with the instrument illumination but have a separate dimmer characteristic.

Display illumination (model 170)
When the vehicle lights are switched off (daytime) the brightness of the display is actuated with the daytime basic value. When the vehicle lights are switched on (night-driving or day-driving light) the brightness can be controlled between the limit values nighttime (min) and nighttime (max).

Display illumination (models 129, 140 as of 06.97 and 202, 208, 210)
A distinction is made between two cases depending on the brightness of the surroundings which is measured by a phototransistor (pt):
- Above the brightness of the surroundings H (nighttime) The phototransistor controls the brightness of the display. The brightness of the display increases as the brightness of the surroundings increases, the dimmer setting has no influence.
- Below the brightness of the surroundings H ( nighttime) the brightness of the display depends on the brightness of the surroundings and the dimmer setting, the higher value applying.

The new brightness stage is always adjusted only after approx. 3 seconds.
The brightness of the display is independent of the vehicle lights.

Display activation
- The display is activated when terminal 15R is ON. It still remains active for approx. 30 seconds after terminal 15R is switched off.
- The display is activated when terminal 15R is OFF:
- by switching on the vehicle lights (terminal 58k ON). The display still remains active for approx. 30 seconds after terminal 58k is switched off.
- The display is activated for approx. 30 seconds or the active phase is extended for a further 30 seconds by opening the driver's door (closing the door contact). On models 202 and 210 the display is also active for approx. 30 seconds after the driver's door is closed.

Model 129 only
The display is activated for approx. 30 seconds or the active phase is extended for a further 30 seconds by pressing the left control button.

Models 140, 163, 168 and 170 only
The display is activated for approx. 30 seconds or the active phase is extended for a further 30 seconds by pressing one of the control buttons.

Models 202, 208 and 210 only
The display is activated for approx. 30 seconds or the active phase is extended for a further 30 seconds by pressing one of the control buttons "odometer reset", "clock setting in hours" or "clock setting in minutes"