PULSED ANTENNA CAPACITIVE TOUCH SWITCH
First Claim
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1. A capacitive touch switch comprising:
- an electrically insulating touch surface providing touch area for activation of the touch switch;
a sense electrode positioned behind the touch surface at the touch area;
an antenna electrode positioned behind the touch surface proximate to the sense electrode;
a reference electrode positioned behind the touch surface proximate to the antenna electrode but removed from the touch area relative to the sense electrode;
a detector circuit monitoring the capacitive coupling between the antenna electrode and each of the sense electrode and reference electrode to provide a switch output based on a comparison of the capacitive coupling between the antenna electrode and the sense electrode compared to a threshold that is a function of the capacitive coupling between the antenna electrode and the reference electrode;
whereby effects of capacitive coupling to surface contamination on the touch surface may be minimized.
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Abstract
A capacitive touch switch suitable for use in areas with high environmental and electrical contamination employs a complex excitation signal that is demodulated to better distinguish it from environmental effects. Improved discrimination allows these sensed signals to be offset against a signal developed by a reference electrode to allow the system to operate robustly with contamination on the electrodes that would otherwise trigger or obscure pulses.
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Citations
14 Claims
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1. A capacitive touch switch comprising:
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an electrically insulating touch surface providing touch area for activation of the touch switch; a sense electrode positioned behind the touch surface at the touch area; an antenna electrode positioned behind the touch surface proximate to the sense electrode; a reference electrode positioned behind the touch surface proximate to the antenna electrode but removed from the touch area relative to the sense electrode; a detector circuit monitoring the capacitive coupling between the antenna electrode and each of the sense electrode and reference electrode to provide a switch output based on a comparison of the capacitive coupling between the antenna electrode and the sense electrode compared to a threshold that is a function of the capacitive coupling between the antenna electrode and the reference electrode; whereby effects of capacitive coupling to surface contamination on the touch surface may be minimized. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification