Trw Automotive Electronics & Components Gmbh

Wulf Reise

Ulrich Backes

A pushbutton switch has a pressure switching function to recognize a key actuation and a capacitive sensor function to recognize a key touch. It has an at least partly electrically conductive key () and a printed circuit board () which includes at least one electrical contact () that is activated by depressing the key () via a switching mat () arranged between the key () and the printed circuit board (). The printed circuit board () also has at least one capacitive sensor surface () located opposite to and at a distance from the key (), with a capacitive coupling existing between the key () and the sensor surface ().

Push-button switch having capacitive and mechanical functionality

In a method of determining a position of a touch on a capacitive sensor field having a grid of a plurality of discrete electrodes (), contacted electrodes are determined by measuring a capacitance value for each of the electrodes and by checking for each of the electrodes for the measured capacitance value whether this value is above a predefined threshold value. A rough touch position (B) is calculated by weighting the electrode position with the measured capacitance value. A touch diameter () is calculated from the measured capacitance values, and a final touch position (B) is calculated from the rough touch position (B) and the calculated touch diameter () using a value table in which correction values that were determined empirically or by means of simulation are stored for possible rough touch positions (B) and given touch diameters ().

Method for determining a position of a contact on a capacitive sensor field

A capacitive rotary encoder has a stator and a rotor as well as stator electrodes firmly arranged at the stator on an encoding path coaxial to the rotor axis, and coupling electrodes arranged at the rotor. The coupling electrodes are guided over the stator electrodes at a small axial distance from the encoding path by rotation of the rotor, wherein they each cover stator electrodes adjacent in the peripheral direction and connect the latter capacitively to each other. Interrogation electronics detects for each of the stator electrodes a capacitive coupling with an adjacent stator electrode caused by a coupling electrode of the rotor. This permits the reliable detection of the angular position of the rotor both statically and dynamically.

Growing community of inventors

Constance, Germany

Wulf Reise