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E90 General Vehicle Electrical
With the aid of 3 sensors, the TAGE module detects the status of the outer door handle.
Each change in the status of the outer door handle module triggers on of the corre-
sponding functions:
• Trigger pulse when a hand is moved around the outer door handle; capacitive sensor
1
• Unlock request by pulling the outer door handle; Hall sensor
• Lock request by touching the recognition point/area on the outer door handle;
capacitive sensor 2
Sensors
To protect the battery, the TAGE module switches off the capacitive sensors for the dri-
ver's side after the vehicle has been at rest for 192 hours. The capacitive sensors on the
passenger's side are switched off after 72 hours.
Functional Principle of the Capacitive Sensor
The capacitive sensor consists of three capacitor plates (electrodes). The dielectric is the
air gap between the door handle and the body/door panel of the vehicle. One capacitor
plate is the car body including the surrounding vehicle. The other two capacitor plates
are located in the outer door handle.
The outer door handle is split in two parts with respect to the capacitor plates. One
capacitor plate is in the outer door handle. The other capacitor plate is contained in the
grooved area on the upper portion of the outer door handle. The functional principle of
the capacitive sensor is based on a change in the electrical field between the capacitor
plates, which results in a change in the capacitance of the capacitor. A change in capaci-
tance occurs (increase) whenever a hand is placed between the body and the outer door
handle (grabbing of the handle). The electronic circuitry in the outer door handle wakes
up based on a defined change in capacitance, which is referred to as triggering.
The capacitive sensor responds with a pulse only to fast changes in its capacitance.
Changes in its environment such as slow soiling of the outer door handle or rain therefore
have no influence on the function of the capacitive sensor.
When unlocking/locking the vehicle, the sensors are mutually blocked for a period of 2
sec., meaning that after locking, unlocking is inhibited for 2 sec and vice versa.
Capacitive Sensor 1
Capacitive Sensor 1 is responsible for initiating the Unlock request by generating pulse
when a hand is held between the "capacitor plates", door handle and door panel/body.
The pulse wakes up the electronic circuitry in the TAGE. If the vehicle is in sleep mode,
the TAGE will send a wake up request via K-Bus to the Comfort Access Module and
CAS2. CAS2 will request that a signal be sent from the external antenna to the ID
Transmitter asking for a validation signal. The Comfort Access module switches on the
remote control receiver in order to receive the validation signal sent from the ID transmit-
ter.
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