Setting pushbutton unit illumination, function

P54.30-8448-09

Data flow image for circuit 58d

A1 Instrument cluster

B38/2 Rain/light sensor

E17/11 Left front door inside handle illumination

E17/12 Right front door inside handle illumination

E17/13 Left rear door inside handle illumination

E17/14 Right rear door inside handle illumination

N10/8 Rear SAM control unit

N69/1 Door control unit front left

N69/2 Door control unit front right

N70 Overhead control panel control unit

N72/1 Upper control panel control unit

S1 Exterior lamp switch

Function requirements:

The switch and controls illumination is activated by the following components:

 Switch on the vehicle lighting (as long as the standing lamp is active);

 with automatic driving lights via the rain/light sensor.

When the standing lamp is switched on the position of the instrument and controls illumination button, dim (A1s5) of instrument and controls illumination button, bright (A1s4) is used as a controlled variable by the overhead control panel control unit. The rain/light sensor is not taken into account.
When automatic driving lights are on, the brightness of the switch and controls illumination is determined via the rain/light sensor.
Its signals are evaluated by the overhead control panel control unit and thus the brightness is regulated via the control unit.

Presentation of duty cycle

Time

Time

T

T 1

U58d

Duty cycle 80 %

T

T 1

U58d

Duty cycle 40 %

Terminal 58d on/off ratio

The lamps of the switch and controls illumination are actuated by means of a square-wave voltage U58d (see top illustration):

 The lamps are energized in the time t1, this is then followed by a break. The lamps are energized again after the break and so on.
The change occurs so quickly as to remain imperceptible to the human eye.

 The ratio of times t1 to T is called the duty cycle. where T is the constant cycle duration and t1 is the time during which power flows during a cycle.

 The greater the duty cycle (that is to say the power flow duration t1)), the greater the average power and therefore the brighter the lamps.

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The voltage curve U58d is sketched in the illustration as it is applied to the outputs "Circuit 58d" of the various control units. The upper sketch shows a duty cycle of 80 %, the lower a duty cycle of 40 %.
A duty cycle of 100 % corresponds to normal direct voltage. Power is not supplied when the duty cycle is 0 %.

Advantages of this type of illumination adjustment:

 Considerably more efficient,

 The brightness of the lamps remains independent of the number of lamps.

 Each control unit, which is connected to the interior CAN or engine compartment CAN, can actuate lamps with the brightness specified by the instrument cluster.

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 When the standing lamp is OFF, the instrument cluster sends the message "circuit 58d duty cycle = 0 %".

When the standing lamp is "ON" the transmitted duty cycle can be adjusted with the instrument and controls illumination button, dim or instrument and controls illumination button, bright from 12 % to 100 %.