Electric field proximity keyboards and detection systems

An electric field proximity keyboard on a substrate, comprising:

• 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 the 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 and wherein the object in close proximity or touching the keypad disturbs the electric field attenuating the voltage at the second node and the voltage difference between the first and second nodes indicates the distance of the object to the keypad.

An electric field proximity keyboard on a substrate, comprising:

• a plurality of keypads each having as follows:
• 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;
• a detector circuit generating a DC output based on the voltage difference across the first node and the second 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;
• and
• a controller coupled to the DC output and the analog multiplexer, wherein the controller issues control commands to the analog multiplexer to selectively couple the 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, wherein the plurality of keypads is arranged in a m×n array with m rows and n columns, wherein each keypad include an electrode pair including a row electrode coupled to a row address and a column electrode coupled to a column address, wherein the quantity of keypads is increased by m×n while the I/O addresses are determined by m+n.