Electric field proximity keyboards and detection systems
First Claim
1. An electric field proximity keyboard on a substrate, comprising:
- a plurality of keypads each having an electrode radiating an electric field;
a circuit including as follows;
a high impedance circuit having a first node and a second node;
an AC signal source coupled to the first node;
an analog multiplexer having an output coupled to the second node, and having a plurality of inputs wherein each input is coupled to one electrode;
a detector circuit generating a DC output based on the voltage difference across the first node and the second node; and
a controller coupled to DC output and the analog multiplexer wherein the controller issues control commands to the analog multiplexer to selectively couple each electrode to the second node for a predetermined time period and to determine whether the DC output indicates a disturbance in the electric field from an object in close proximity or touching the keypad.
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Accused Products
Abstract
The invention is related to an electric field proximity detection system suitable for use as a touch sensitive keyboard or to be used in close proximity without direct contact. In an embodiment of a circuit useful in the system, an AC signal is coupled to a single electrode functioning as an antenna radiating an electric field through a high impedance circuit. A conductive object in close proximity disturbs the field causing a voltage change across nodes of the high impedance circuit that is compared by a detector circuit that generates a DC output indicating an object is close to the electrode. In another embodiment, the circuit couples to an analog multiplexer to control a plurality of electrodes. In another embodiment, a row and column address scheme coupling a plurality of electrodes and increases resolution without substantially increasing complexity. The circuits may be integrated in a semiconductor to reduce size and cost. The electric field proximity detection system extends to applications related to object detection such as remote sensing, motion detection and remote controls.
72 Citations
14 Claims
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1. An electric field proximity keyboard on a substrate, comprising:
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a plurality of keypads each having an electrode radiating an electric field;
a circuit including as follows;
a high impedance circuit having a first node and a second node;
an AC signal source coupled to the first node;
an analog multiplexer having an output coupled to the second node, and having a plurality of inputs wherein each input is coupled to one electrode;
a detector circuit generating a DC output based on the voltage difference across the first node and the second node; and
a controller coupled to DC output and the analog multiplexer wherein the controller issues control commands to the analog multiplexer to selectively couple each electrode to the second node for a predetermined time period and to determine whether the DC output indicates a disturbance in the electric field from an object in close proximity or touching the keypad. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An electric field proximity keyboard on a substrate, comprising:
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a keypad having an electrode radiating an electric field;
a circuit including as follows;
a high impedance circuit having a first node and a second node;
an AC signal source, wherein the AC signal source is coupled to the first node and the electrode is coupled to the second node;
a detector circuit generating a DC output based on the voltage difference across the first node and the second node; and
a controller coupled to DC output wherein the controller determines whether the DC output indicates a disturbance in the electric field from an object in close proximity or touching the keypad. - View Dependent Claims (12, 13, 14)
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Specification