Force sensor with compressible electrode

• US 8,621,942 B2
• Filed: 08/03/2009
• Issued: 01/07/2014
• Est. Priority Date: 08/03/2009
• Status: Active Grant

• Current Assignee: Neodrón Limited (Atlantic IP Services Limited)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Sleeman, Peter
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): DAVIS HOLLINGTON, OCTAVIA L
• Application Number:
  US12/534,753
• Publication Number:
  US 20110023631A1
• Time in Patent Office: 1,618 Days
• Field of Search: 738/626.26, 737/80, 738/626.8
• US Class Current: 73/862.626
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

A sensor includes a first electrode and a second, compressible electrode. A dielectric layer separates the first electrode from the second electrode. At least one of the first and second electrodes compress responsive to force, increasing capacitance between the first and second electrodes.

Claims

1. A sensor comprising:

a first sensor portion comprising;

a first portion, the first portion comprising a plurality of electrodes arranged along a first axis, the first portion configured to detect a location with respect to the first axis of a touch on part of the first portion;

a second portion distinct from the first portion, the second portion comprising a first electrode;

a second sensor portion comprising a second electrode;

a dielectric layer separating the first electrode from the second electrode, wherein the second electrode compresses responsive to force such that the second electrode increases in surface area relative to the first electrode, increasing capacitance between the first and second electrodes.

2. The sensor of claim 1 wherein the second electrode is formed as a compressible tube or cylinder.

3. The sensor of claim 1 wherein the second electrode is formed as a compressible element with a cross section that tapers to become narrower close to the first electrode.

4. The sensor of claim 3 wherein the compressible tube or cylinder is formed of carbon impregnated compressible material.

5. The sensor of claim 3 wherein the compressible tube or cylinder is formed of a metal loaded or metal coated compressible material.

6. The sensor of claim 5 wherein the compressible material is neoprene.

7. The sensor of claim 1 and further comprising:

a front panel disposed over the first electrode opposite the dielectric layer; and

a support layer disposed under the second electrode opposite the dielectric layer.

8. The sensor of claim 1 wherein the second electrode compresses responsive to force, such that portions of the second electrode move closer to the first electrode.

9. The sensor of claim 1 wherein the first electrode is a conductive plane to couple to a DC potential.

10. The sensor of claim 9 and further comprising a self capacitance sensing circuit coupled to the second electrode.

11. The sensor of claim 1 wherein the first electrode is a transmit electrode for coupling to a driver circuit, and the second electrode is a receive electrode for coupling to a capacitive measurement circuit.

12. A system comprising:

a sensor comprising;

a first portion, the first portion comprising a plurality of electrodes arranged along a first axis, the first portion configured to detect a location with respect to the first axis of a touch on part of the first portion;

a second portion distinct from the first portion, the second portion comprising a transmit electrode;

a driver circuit coupled to the transmit electrode;

a receive electrode;

a capacitive measurement circuit coupled to the receive electrode; and

a dielectric layer separating the transmit electrode from the receive electrode;

wherein the receive electrode compresses responsive to force such that the receive electrode increases in surface area relative to the transmit electrode, increasing capacitance between the transmit and receive electrodes.

13. The system of claim 12 wherein at least one of the transmit electrode and receive electrode is formed as a compressible tube or cylinder.

14. The system of claim 13 wherein the compressible tube or cylinder is formed of carbon.

15. The system of claim 13 wherein the compressible tube or cylinder is formed of a metal loaded or metal coated compressible material.

16. The system of claim 12 and further comprising:

a front panel disposed over the transmit electrode opposite the dielectric layer; and

a support layer disposed under the receive electrode opposite the dielectric layer.

17. The system of claim 12 wherein the receive electrode compresses responsive to force, such that portions of the receive electrode move closer to the transmit electrode.

18. A method comprising:

forming a sensor between a front panel and a substrate, the sensor comprising;

a first portion, the first portion comprising a plurality of electrodes arranged along a first axis, the first portion configured to detect a location with respect to the first axis of a touch on part of the first portion;

a second portion distinct from the first portion, the second portion comprising a first electrode;

forming a second electrode in capacitive relationship with the first electrode between the substrate and a support, wherein the second electrode is formed such that the second electrode compresses responsive to force and increases in surface area relative to the first electrode; and

wherein the capacitance between the first and second electrodes increases responsive to force applied to the front panel proximate the first and second electrodes.

19. The method of claim 18 wherein the second electrode is formed as a compressible tube.

20. The method of claim 18 and farther comprising:

providing a front panel disposed over the first electrode opposite the substrate; and

providing a support layer disposed under the second electrode opposite the substrate.

21. The method of claim 18 wherein the second electrode is formed such that it compresses responsive to force, and portions of the second electrode move closer to the first electrode.