Capacitor touch activated switching system

• US 4,595,913 A
• Filed: 02/10/1983
• Issued: 06/17/1986
• Est. Priority Date: 02/10/1983
• Status: Expired due to Fees

• Current Assignee: PIE Associates
• Original Assignee: PIE Associates
• Inventors: Aubuchon, Vaughn F.
• Primary Examiner(s): Groody, James J.
• Application Number:
  US06/465,601
• Time in Patent Office: 1,223 Days
• Field of Search: 340/365 C, 340/365 S, 340/365 E, 340/712, 200/DIG. 1, 307/116, 400/479.1
• US Class Current: 341/33
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard

Abstract

A touch sensitive system comprising a clock (30) for generating a clocking signal supplied to a plurality of circuits each including one of the touch plates (12, 14, 15, 16, 17) for generating a varying capacitance value depending upon whether or not the plate is touched or untouched. The change in capacitance of each circuit varies the time duration of the generated output signal of that circuit. A flipflop (18, 19, 20, 21, 22) for each circuit receives a reference signal from a reference circuit (61) and the output signal from the associated circuit and supplies to an associated output terminal (24, 25, 26, 27, 28) a digital signal indicating which plate or plates are touched.

Claims

1. A switching mechanism for generating an output signal responsive to the touch of an operator, comprising:

a clocking signal generator;

a first circuit connected with said touch plate in a manner to effect a different time delay in the transmission of said clocking signal when said plate is touched and untouched;

means for conducting said clocking signal to said first circuit;

means for generating an output signal indicating the time delay effected on said clocking signal thereby to indicate whether the plate is touched or untouched;

said first circuit including an RC circuit with the touch plate forming at least a portion of the capacitive component of the RC circuit;

a NAND gate having first and second terminals with the first terminal connected to receive the output signal from said first circuit and the second terminal connected to receive said clocking signal with said means for generating an output signal receiving the output signal from said NAND gate;

a flip flop circuit having first and second input terminals;

means for transmitting the output signal from said NAND gate to said first terminal of said flip flop circuit;

a second circuit including an RC circuit;

means for transmitting the clocking signal to said second circuit; and

means for transmitting the output signal from said second circuit to the second input terminal of said flip flop whereby the flip flop will generate an output signal responsive to the relative duration of said output signals received at the first and second flip flop input terminals to indicate whether the touch plate is touched.

2. A switching mechanism for generating an output signal responsive to the touch of an operator, comprising:

a touch plate having a surface to be selectively touched by the operator;

a clocking signal generator;

a first one-shot connecting with said touch plate and connected to receive said clocking signal to generate an output signal having first and second time durations responsive to whether or not the touch plate is touched by the operator;

a variable capacitor;

a second one-shot connected to receive said clocking signal to generate an output signal having a time duration dependent on the capacitance of said variable capacitor;

a flip flop having input terminals connected to receive the output signals from said first and second one-shots and generating an output signal responsive to which of the one-shot signals has the longest time duration.