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Annular potentiometric touch sensor

  • US 7,554,531 B2
  • Filed: 12/02/2005
  • Issued: 06/30/2009
  • Est. Priority Date: 05/18/2004
  • Status: Active Grant
First Claim
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1. An annular touch sensor comprising:

  • a bottom substrate;

    an annular pattern of resistive material traversing a portion of a top surface of the bottom substrate;

    a plurality of conductive drive lines, each conductive drive line radially traversing the top surface of the bottom substrate so as to be electrically coupled with the annular pattern of resistive material;

    a plurality of fixed potential conductive traces, each fixed potential conductive trace radially traversing the top surface of the bottom substrate and electrically coupled with the annular pattern of resistive material;

    a conductive sense line having a plurality of conductive sense traces, each sense trace electrically decoupled from the annular pattern of resistive material, the fixed potential conductive traces, and the drive lines when the sensor is untouched, and each sense trace radially traversing the top surface of the bottom substrate;

    a top substrate spaced above the top surface of the bottom substrate;

    a conductive layer on a bottom surface of the top substrate, the conductive layer positioned above one or more of the annular pattern, the fixed potential conductive traces, and the conductive sense traces;

    wherein a pressure applied to at least one of the top substrate and the bottom substrate electrically couples a portion of one or more of the conductive sense traces to a portion of at least one of the annular pattern and one or more of the fixed potential conductive traces; and

    a processor in electrical communication with the conductive sense line and the plurality of conductive drive lines, the processor operative to;

    determine a conductive drive line closest to the applied pressure;

    apply a potential across a first remote conductive drive line and a second remote conductive drive line, wherein the first and second remote conductive drive lines are electronically distinct from the conductive drive line closest to the applied pressure;

    measure a sense voltage between the conductive sense line and one of the first and second remote conductive drive lines; and

    determine an angular position of the applied pressure about the touch sensor using the sense voltage.

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