Capacitive touch switch array

• US 4,233,522 A
• Filed: 10/30/1978
• Issued: 11/11/1980
• Est. Priority Date: 10/30/1978
• Status: Expired due to Term

• Current Assignee: General Dynamics Defense Systems Incorporated (General Dynamics Corporation)
• Original Assignee: General Electric Company
• Inventors: Hendriks, Hendrik B., Grummer, William L.
• Primary Examiner(s): Hix, L. T.
• Assistant Examiner(s): Brady, W. J.
• Application Number:
  US05/956,278
• Time in Patent Office: 743 Days
• Field of Search: 307/116, 200/DIG. 1, 340/365 C, 361/181, 361/280, 331/65
• US Class Current: 341/33
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2017/9613 using two electrodes per touch switch

Abstract

A capacitive touch panel comprising an array of touch sensitive switch cells, the panel including relatively small area touch switch elements located on closely spaced centers, that can be of transparent construction particularly suited for use with data processing equipment and electronic displays. Each switch cell includes a first and a second pair of series connected capacitors energized by a common signal source, the array of switch cells being arranged so that the first pair of capacitors are connected in first groups of switch cells, such as rows, to a corresponding first plurality of signal detectors, and the second pair of capacitors are connected in second groups of switch cells, such as columns, to a corresponding second plurality of signal detectors, the junctions of each pair of capacitors of a single switch cell being selectively coupled to ground by the body or other touch capacitive means for actuating a selected switch cell.

Claims

1. A capacitive touch switch array, comprising:

(a) an array of touch sensitive switch cells each including a first pair of series capacitors and a second pair of series capacitors,

(b) a signal source coupled to said first and second pair of series capacitors,

(c) first signal detection circuit means, said first pair of series capacitors coupling the signal from said signal source to said first signal detection circuit means,

(d) second signal detection circuit means, said second pair of series capacitors coupling the signal from said signal source to said second signal detection circuit means, and

(e) touch means associated with each switch cell for providing capacitive coupling of the junctions of each pair of series capacitors of a selected switch cell to ground for actuating said selected switch cell and varying the signal coupled by the first and second pair of series capacitors of said selected switch cell to said first and second signal detection circuits means.

2. A capacitive touch switch array as in claim 1 wherein the switch cells of said array are arranged in first and second groups that define a system of coordinates for specifying the location of each switch cell within said array, said first signal detection circuit means includes a first plurality of detection circuits and said second signal detection circuit means includes a second plurality of detection circuits, the first pairs of series capacitors in said switch cells are each connected to corresponding detection circuits within said first plurality of detection circuits in accordance with parameters of said system of coordinates established by said first groups of switch cells with each said first pair of series capacitors in said first group of said switch cells having the same address in the system of coordinates being connected to the same said detection circuit, and the second pairs of series capacitors in said switch cells are each connected to corresponding detection circuits within said second plurality of detection circuits in accordance with parameters of said system of coordinates established by said second groups of switch cells with each said second pair of series capacitors in said second group of said switch cells having the same address in the system of coordinates being connected to the same said detection circuit.

3. A capacitive touch switch array as in claim 2 wherein said signal source generates a signal that is commonly applied to each of the switch cells of said array.

4. A capacitive touch switch array as in claim 3 wherein said array further comprises means for addressing said first and second plurality of detection circuits in a predetermined manner for generating therefrom an output in accordance with the state of the detection circuits addressed.

5. A capacitive touch switch array as in claim 2 wherein said first and second pair of series capacitors and said touch means of each switch cell are integrally constructed in the form of a touch panel, said first pair of series capacitors of switch cells within each group of said first groups of switch cells are connected in parallel, and said second pair of series capacitors of switch cells within each group of said second groups of switch cells are connected in parallel, whereby the effective series capacitance of said first pair of series capacitors of each switch cell and the effective series capacitance of said second pair of series capacitors of each switch cell, respectively, are increased over that of an individually connected first and second pair of series capacitors by a multiple substantially equal to the number of switch cells within each group.

6. A capacitive touch switch array as in claim 5 wherein said touch panel comprises a dielectric layer having a first pattern of capacitor touch plates on one surface thereof and a second pattern of input capacitor plate means and output capacitor plates on an opposing surface thereof, each of said switch cells including first and second capacitor touch plates, input capacitor plate means coupled to said signal source, a first output capacitor plate coupled to said first plurality of detection circuits and a second output capacitor plate coupled to said second plurality of detection circuits, said first pair of capacitors of each switch cell being formed between said input capacitor plate means, a first capacitor touch plate and a first output capacitor plate, respectively, and said second pair of series capacitors of each switch cell being formed between said input capacitor plate means, a second capacitor touch plate and a second output capacitor plate, respectively.

7. A capacitive touch switch array as in claim 6 wherein said input capacitor plate means comprise a plurality of input capacitor plates that are each common to the first and second pair of series capacitors of at least a single switch cell.

8. A capacitive touch switch array as in claim 7 wherein said first groups of switch cells are rows, said second groups of switch cells are columns, said first plurality of detection circuits includes a row detection circuit corresponding to each row of switch cells and said second plurality of detection circuits includes a column detection circuit corresponding to each column of switch cells, within each row of switch cells said first capacitor touch plates being coupled together and said first output capacitor plates being coupled together and to a corresponding row detection circuit, within each column of switch cells said second capacitor touch plates being coupled together and said second output capacitor plates being coupled together and to a corresponding column detection circuit, and said input capacitor plates being coupled together within the entire array of switch cells.

9. A capacitive touch switch array as in claim 8 wherein said signal source generates a signal that is commonly applied to each input capacitor plate of the switch cells of said array.

10. A capacitive touch switch array as in claim 9 wherein said array further comprises means for scanning said first and second plurality of detection circuits for generating therefrom a sequential output.

11. A capacitive touch switch array as in claim 2 wherein said touch means of each switch cell comprise first and second touch elements that are integrally constructed in the form of a touch panel and said first and second pair of series capacitors are in an electrical circuit separate from said touch panel, said electrical circuit including a first pair of series capacitors corresponding to each group of said first groups of switch cells and to each detection circuit of said first plurality of detection circuits, and a second pair of series capacitors corresponding to each group of said second groups of switch cells and to each detection circuit of said second plurality of detection circuits, said first touch elements of switch cells in each group of said first groups of switch cells being coupled together and to the junctions of corresponding first pairs of series capacitors, and said second touch elements of switch cells in each group of said second groups of switch cells being coupled together and to the junctions of corresponding second pairs of series capacitors.

12. A capacitive touch switch array as in claim 11 wherein said signal source generates a signal that is commonly applied to the inputs of each of said first and second pair of series capacitors, the outputs of each of said first and second pair of series capacitors being coupled to their corresponding detection circuits.

13. A capacitive touch switch array as in claim 12 wherein said array further comprises means for scanning said first and second plurality of detection circuits for generating therefrom a sequential output.

14. A capacitive touch switch array as in claim 11 which includes a plurality of coupling capacitors integrally constructed on said touch panel and serving to couple said first touch elements of switch cells in each group of said first groups of switch cells to the junctions of corresponding first pairs of series capacitors.

15. A capacitive touch switch array as in claim 14 wherein said touch panel comprises a dielectric layer having a first pattern of said first and second touch elements on one surface thereof and a second pattern of capacitor plates on an opposing surface thereof, each of said switch cells further including a capacitor plate, said coupling capacitors being formed between said capacitor plates and said first touch elements.

16. A capacitive touch switch array as in claim 15 wherein said first groups of switch cells are rows, said second groups of switch cells are columns, said second touch elements within each column are coupled together and said capacitor plates within each row are coupled together.

17. A capacitor touch panel including an array of touch sensitive switch cells, said touch panel comprising:

(a) a dielectric layer,

(b) a first pattern of capacitor touch plates on one surface of said dielectric layer, each of said switch cells including first and second capacitor touch plates responsive to touch,

(c) a second pattern of input and output capacitor plates on the opposing surface of said dielectric layer, each of said switch cells further including an input capacitor plate responsive to an input signal source, a first output capacitor plate providing a first output signal and a second output capacitor plate providing a second output signal,

(d) a first pair of series capacitors for each switch cell being formed between said input capacitor plate, a first capacitor touch plate and a first output capacitor plate, respectively, and

(e) a second pair of series capacitors for each switch cell being formed between said input capacitor plate, a second capacitor touch plate and a second output capacitor plate, respectively.

18. A capacitive touch panel as in claim 17 wherein said switch cells are arranged in rows and columns, within each row of switch cells said first capacitor touch plates being coupled together and said first output capacitor plates being coupled together, within each column of switch cells said second capacitor touch plates being coupled together and said second output capacitor plates being coupled together, and said input capacitor plates being coupled together within the entire array of switch cells.

19. A panel including an array of cells arranged in first and second groups that define a system of coordinates for specifying the location of each cell within said array, which cells are individually accessible to external circuitry without a requirement for crossover conductors on said panel, comprising:

(a) a dielectric layer,

(b) a first pattern of first and second electrodes on one surface of said dielectric layer,

(c) a second pattern of third electrodes on an opposing surface of said dielectric layer, each of said cells including a first, second and third electrode, said first and third electrodes being capacitively coupled together through said dielectric layer,

(d) means for coupling said second electrodes together within each group of said second groups of cells and for providing first access means to said external circuitry, and

(e) means for coupling said third electrodes together within each group of said first groups of cells and for providing second access means to said external circuitry.

20. A panel as in claim 19 which includes means for coupling said first electrodes together at least in pairs within each group of said first groups of cells.

21. A capacitive touch switch array, comprising:

(a) an array of touch sensitive switch cells each including at least a pair of series capacitors,

(b) a signal source coupled to said pair of series capacitors,

(c) a signal detection circuit means having parasitic capacitance present between the input of said signal detection circuit means and ground, said parasitic capacitance having a fixed and a variable component,

(d) a discrete capacitor coupled between the input of said signal detection circuit means and ground in parallel with said parasitic capacitance, said discrete capacitor having a value of capacitance large enough to substantially mask the variable component of said parasitic capacitance,

(e) coupling means including said pair of series capacitors and said discrete capacitor for coupling the signal from said signal source to said signal detection circuit means as a voltage divided signal of a first voltage level, and

(f) touch means associated with each switch cell for providing capacitive coupling of the junction of each pair of series capacitors of a selected switch cell to ground for actuating said selected switch cell and further voltage dividing the signal coupled to said signal detection circuit means to a second voltage level, said discrete capacitor serving to stabilize said first and second voltage levels.

22. A capacitive touch switch array, comprising:

(a) an array of touch sensitive switch cells each including a first pair of series capacitors and a second pair of series capacitors,

(b) a signal source coupled to said first and second pair of series capacitors,

(c) first signal detection circuit means having parasitic capacitance between the input of said first signal detection circuit means and ground, said parasitic capacitance having a fixed and a variable component,

(d) a first discrete capacitor coupled between the input of said first signal detection circuit means and ground in parallel with said parasitic capacitance, said first discrete capacitor having a value of capacitance large enough to substantially mask the variable component of said parasitic capacitance,

(e) first coupling means including said first pair of series capacitors and said first discrete capacitor for coupling the signal source to the input of said first signal detection circuit means as a voltage divided signal of a first voltage level,

(f) second signal detection circuit means having said parasitic capacitance between the input of said second signal detection circuit means and ground,

(g) a second discrete capacitor coupled between the input of said second signal detection circuit means and ground in parallel with said parasitic capacitance, said second discrete capacitor having a value of capacitance large enough to substantially mask the variable component of said parasitic capacitance,

(h) second coupling means including said second pair of series capacitors and said second discrete capacitor for coupling the signal from said signal source to the input of said second signal detection circuit means as a voltage divided signal of said first voltage level, and

(i) touch means associated with each switch cell for providing capacitive coupling of the junctions of each pair of series capacitors of selected switch cell to ground for actuating said selected switch cell and further voltage dividing the signal coupled to said first and second signal detection means to a second voltage level, said first and second discrete capacitors serving to stabilize said first and second voltage levels.