Capacitively coupled keypad structure

• US 6,633,241 B2
• Filed: 12/21/2000
• Issued: 10/14/2003
• Est. Priority Date: 12/28/1999
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Salminen, Seppo, Svarfvar, Bror, Kaikuranta, Terho, Vuori, Petri
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): WONG, ALBERT KANG
• Application Number:
  US09/746,464
• Publication Number:
  US 20020093489A1
• Time in Patent Office: 1,027 Days
• Field of Search: 341/20, 341/22, 341/23, 379/433.06, 379/433.07, 379/368, 379/369, 379/370, 345/168, 345/172, 361/680, 455/90.3
• US Class Current: 341/33
• CPC Class Codes: H01H 13/702 with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
• CPC Class Codes: H01H 2239/006 Containing a capacitive switch or usable as such
• CPC Class Codes: H03K 17/98 having a plurality of control members, e.g. keyboard

Abstract

A keypad arrangement for an electronic device comprises a keypad comprising activatable keys. It comprises also input signal means (801, 802, 901, 1001, 1601) for bringing an electric input signal to the keypad, and signal conversion means (703, 705, 807, 808, 809, 810, 811, 812, 813, 818, 1208, 1206) for responding to a key activation by selectively converting the input signal into an electric output signal the value of which depends on the activated key. Additionally there are output signal detection means (902, 903, 904, 1002, 1602) for detecting the value of the electric output signal. The arrangement comprises a first electromagnetic coupling (706, 708, 709, 710, 803) between the input signal means and the signal conversion means, and a second electromagnetic coupling (707, 711, 804) between the signal conversion means and the output signal detection means.

Claims

1. A keypad arrangement for an electronic device, comprising:

a keypad comprising activatable keys,

input signal means for bringing an electric input signal to the keypad,

signal conversion means for responding to a key activation by selectively converting the input signal into an electric output signal the value of which depends on the activated key,

output signal detection means for detecting the value of the electric output signal,

a first capacitive coupling between the input signal means and the signal conversion means, and

a second capacitive coupling between the signal conversion means and the output signal detection means.

2. A keypad arrangement according to claim 1, wherein the signal conversion means comprise:

a resistive strip having a first end and a second end, which first end and second end are coupled to said first capacitive coupling, and comprising a multitude of coupling points at different positions between said first end and said second end, and

means for selectively coupling, as a response to a key action, one of said coupling points at a time to said second capacitive coupling.

3. A keypad arrangement according to claim 2, wherein each of said first end and second end constitutes a capacitive electrode in said first capacitive coupling.

4. A keypad arrangement according to claim 2, wherein said means for selectively coupling one of said coupling points at a time to said second capacitive coupling comprises a continuous conductive element that is located adjacent to said resistive strip and comprises a resilient conductive dome at the location of each coupling point in the resistive strip.

5. A keypad arrangement according to claim 4, wherein said continuous conductive element comprises an extending portion which constitutes a capacitive electrode in said second capacitive coupling.

6. A keypad arrangement according to claim 4, comprising a number of keydomes for providing a tactile surface for each conductive dome in said continuous conductive element.

7. An exchangeable cover for a mobile telecommunication device, comprising:

a keypad that comprises activatable keys,

first capacitive coupling means for capacitively obtaining an electric input signal to the keypad from an external input signal source,

second capacitive coupling means for capacitively providing an output signal from the keypad to an external signal detector, and

between said first capacitive coupling means and said second capacitive coupling means signal conversion means for responding to a key activation by selectively converting an electric input signal into an electric output signal the value of which depends on the activated key.

8. An exchangeable cover according to claim 7, comprising a first set of capacitive electrodes as said first capacitive coupling means and a second set of capacitive electrodes as said second capacitive coupling means, wherein the number of capacitive electrodes in each set is at least one.

9. An exchangeable cover according to claim 8, comprising:

a cover body with a number of holes therethrough, each hole defining a key location,

a resistive strip having a first end and a second end, which first end and second end are coupled to said first set of capacitive electrodes, and comprising a multitude of coupling points at certain positions between said first end and said second end that correspond to the locations of said holes in said cover body,

a continuous conductive element that is located between said resistive strip and said cover body and comprises a resilient conductive dome at the location of each coupling point in the resistive strip, and

a number of keydomes protruding through said holes for providing a tactile surface for each conductive dome in said continuous conductive element.

10. An exchangeable cover according to claim 7, comprising mechanical coupling means for providing a repeatedly disconnectable snap-on coupling between it and the mobile telecommunication device.

11. A set of exchangeable covers for a mobile telecommunication device, comprising:

a first cover and a second cover,

within each of said first and second covers means for mechanically attaching the cover to the same mobile telecommunication device,

within each of said first and second covers a keypad that comprises activatable keys,

within each of said first and second covers first capacitive coupling means for capacitively obtaining an electric input signal to the keypad from an external input signal source,

within each of said first and second covers second capacitive coupling means for capacitively providing an output signal from the keypad to an external signal detector,

within each of said first and second covers signal conversion means for responding to a key activation by selectively converting an electric input signal into an electric output signal the value of which depends on the activated key; and

wherein the first cover has the keys of the keypad at different locations than the second cover.

12. An electronic device, comprising:

a keypad that comprises activatable keys,

an outer cover part,

a printed circuit board,

input signal generating means for generating an input signal to the keypad,

signal conversion means for responding to a key activation by selectively converting the input signal into an output signal the value of which depends on the activated key, and

output signal detection means for detecting the value of the output signal;

wherein;

the input signal generating means and the output signal detection means are located within the printed circuit board,

the signal conversion means are attached to the outer cover part, and

the electronic device comprises a first capacitive coupling between the input signal generating means and the signal conversion means, and a second capacitive coupling between the signal conversion means and the output signal detection means.

13. An electronic device according to claim 12, comprising:

within the printed circuit board an AC voltage generator for generating an AC voltage signal as an input signal to the keypad,

within the printed circuit board a first set of capacitive electrodes as a part of said first capacitive coupling means, said first set of capacitive electrodes being coupled to said AC voltage generator,

within the signal conversion means a second set of capacitive electrodes as a part of said first capacitive coupling means,

within the signal conversion means and coupled to said second set of capacitive electrodes a resistive strip having a first end and a second end comprising a multitude of coupling points at different positions between said first end and said second end,

within the signal conversion means a third set of capacitive electrodes as a part of said second capacitive coupling means,

within the signal conversion means and coupled to said third set of capacitive electrodes means for selectively coupling, as a response to a key activation, one of said coupling points at a time to said third set of capacitive electrodes,

within the printed circuit board a fourth set of capacitive electrodes as a part of said second capacitive coupling means,

within the printed circuit board and coupled to said fourth set of capacitive electrodes a peak detector for detecting an extreme value of an output AC voltage signal; and

wherein the number of capacitive electrodes in each set of capacitive electrodes is at least one.

14. An electronic device according to claim 13, further comprising, between said AC voltage generator and said first set of capacitive electrodes, switching means for selectively coupling the AC voltage signal generated by said AC voltage generator to said first set of capacitive electrodes with different polarities.

15. An electronic device according to claim 14, further comprising, coupled to said peak detector, means for selectively storing at least two detected extreme values in synchronism with the operation of said switching means so that said two detected extreme values correspond to different polarities of the AC voltage signal generated by said AC voltage generator.

16. An electronic device according to claim 12, wherein the output signal detection means comprise a mean value storage and comparator for storing detected values associated with previous key activations and for comparing a detected output signal value against the stored values.