Charge rate, capacitive switch system
First Claim
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1. A capacitive switch system comprising:
- a plurality of conductor means;
a plurality of capacitive switches;
each said capacitive switch coupled between a unique pair of said conductor means;
means for sequentially interrogating each said conductor means;
a reference capacitance; and
a capacitor detector for simultaneously comparing the capacitance associated with a said interrogated conductor means with said reference capacitance;
said sequential interrogating means including switching means coupled to said conductor means and said detector for coupling each said interrogated conductor means to said detecting means for simultaneously charging and discharging said reference capacitance and the capacitance associated with an interrogated said conductor means.
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Abstract
A plurality of capacitive switches, which are actuated by the touch of a user, are coupled to unique pairs of conductors. The conductors are sequentially actuated, or interrogated, and simultaneously coupled to a charge rate detector that compares the capacitance associated with each conductor to a reference capacitor. Storage means coupled to the output of the charge rate detector stores an indication of whether the capacitance associated with each conductor is greater or less than the reference capacitor such that the stored indications constitute a two of N code that identifies an actuated capacitive switch.
49 Citations
23 Claims
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1. A capacitive switch system comprising:
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a plurality of conductor means; a plurality of capacitive switches; each said capacitive switch coupled between a unique pair of said conductor means; means for sequentially interrogating each said conductor means; a reference capacitance; and a capacitor detector for simultaneously comparing the capacitance associated with a said interrogated conductor means with said reference capacitance; said sequential interrogating means including switching means coupled to said conductor means and said detector for coupling each said interrogated conductor means to said detecting means for simultaneously charging and discharging said reference capacitance and the capacitance associated with an interrogated said conductor means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 23)
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10. A capacitive switch system comprising:
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a plurality of conducting means; a capacitive switch coupled between at least a pair of said conducting means; scanning means for sequentially interrogating the conducting means; a capacitance detector sequentially coupled to said conducting means in synchronism with said scanning means for detecting capacitance associated with each said conducting means and a reference capacitor coupled to said detector; and
means coupled to said detector for simultaneously charging and discharging said reference capacitor and the capacitance associated with an interrogated conductor for enabling said detector means to simultaneously compare the charge rate of said reference capacitor with the charge rate of the capacitance associated with an interrogated conducting means. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. The method of determining whether any of a plurality of capacitive switches are actuated when each of the plurality of capacitive switches are coupled to a pair of unique conductors with each conductor being coupled to more than one capacitive switch, comprising the steps of:
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sequentially coupling each of the conductors to a single capacitive detector that includes a reference capacitor, simultaneously charging and discharging the reference capacitor and the capacitance of a conductor coupled to the detector with the capacitance of the conductor being greater than the reference capacitance when a switch coupled thereto is actuated and with the capacitance of the conductor being less than the reference capacitance when none of the switches coupled thereto are actuated; and comparing the charge rate of the reference capacitor with the charge rate of the capacitance associated with the conductor coupled to the detector to determine whether the capacitance of the conductor coupled to the detector is greater or less than the reference capacitor. - View Dependent Claims (19, 20, 21, 22)
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Specification