Patent ID: 6954867

Claim:
A capacitive sensing system for sensing the presence of an object or body portion in contact with or close proximity to another object, comprising: a first conductor capacitively coupled to a ground to thereby form a scoop capacitor having a capacitance which varies in relation to the proximity of said object or body portion to said conductor; a pair of second and third conductors forming a bucket capacitor having a capacitance which is larger than a maximum capacitance of said scoop capacitor; an input threshold switch; charge setting means for setting a charge of said bucket capacitor at a repeatable non-zero reference level; switching means for selectively: connecting at least one of said scoop capacitor and bucket capacitor to a voltage source to charge said at least one capacitor, connecting said charge setting means to said bucket capacitor to set the charge of the bucket capacitor to said repeatable non-zero reference level, varying the charge of said bucket capacitor from the reference level set by said charge setting means, in relation to a relative size of said scoop capacitor, and applying a voltage of said bucket capacitor to said input threshold switch; detector means for detecting an input state of said input threshold switch; determining means for determining a value (TouchVal) relating to a number of cycles of said varying of the bucket capacitor charge, corresponding to a detection of a transition of said input threshold switch by said detector means; and signal generating means for generating, based upon TouchVal, a signal indicative of an ON state wherein said object or body portion is in contact with or close proximity to said another object, and an OFF state wherein said object or body portion is not in contact with or close proximity to said another object.