Capacitive transducer apparatus and method of manufacture thereof for computer display user interface

Abstract

A capacitive transducer apparatus converts mechanical force to electrical signal parameters by change of spacing between plates of a plurality of capacitors. The apparatus has two mechanical components. The first component includes an articulating member such as a post surrounded by a first capacitive plate. Means are provided for causing the articulating member to articulate responsive to user manipulation thereof, and thereafter, to return to a quiescent position. The second component includes a second capacitive plate made up of a plurality of printed metalized members disposed about the articulating member substantially parallel to the first capacitive plate. A circuit is provided for detecting respective signals from a plurality of capacitors formed by the plates, the respective signals varying in value depending on articulation of the articulating member which alters the capacitance of the respective capacitors depending on the direction and magnitude of an applied force. The capacitors preferably include flat, electrically conductive members on a planar substrate, such as etched conductive regions on a printed circuit board, and the articulating member includes an electrically conductive member whose varying proximity to the conductive region, due to the manipulation by the user, produces a correspondingly varying capacitance value. The magnitude of the capacitance is determined by a data acquisition system, preferably including RC oscillators and a microcontroller.