Touch Sensitive Controls With Weakly Conductive Touch Surfaces

• US 20090290742A1
• Filed: 05/22/2008
• Published: 11/26/2009
• Est. Priority Date: 05/22/2008
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Plantronics, Inc. (HP Inc.)
• Inventors: Rosener, Douglas K.
• Granted Patent: US 9,280,239 B2
• Time in Patent Office: Days
• US Class Current: 381/375
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/960755 Constructional details of capacitive touch and proximity switches

Abstract

A touch activated control useful for incorporation into, e.g., a DON/DOFF sensor of a communications headset or a touch pad for a cell phone, includes a weakly conductive electrode and a sensor coupled to the electrode and operative to detect a change in parasitic capacitance caused by a change in the proximity of a body to the electrode. The electrode may include a covering made of a weakly conductive material. The weakly conductive property of the electrode enables the prevention of undesirable electrostatic discharge (ESD), user skin irritation and electrode corrosion caused by direct contact between the electrode and the user'"'"'s skin and also exhibit'"'"'s a substantially higher sensitivity than electrodes covered with an insulative material.

Claims

1. A touch-activated apparatus, comprising:

an electrode;

a sensor coupled to the electrode and operative to detect a change in parasitic capacitance caused by a change in the proximity of a body to the electrode; and

,

a weakly conductive covering disposed over the electrode and arranged to be contacted by the body.

2. The apparatus of claim 1, wherein the weakly conductive covering comprises an electrostatic charge dissipative material.

3. The apparatus of claim 1, wherein the weakly conductive covering comprises a thermoplastic polyolefin elastomer (TEO) having a volume resistivity of from about 1.0E3 to about 9.9E9 ohm.cm.

4. The apparatus of claim 1, wherein the weakly conductive covering comprises an elastomer containing particles of an electrically conductive material.

5. The apparatus of claim 1, wherein:

the electrode comprises an earpiece of a communications headset; and

,

the apparatus comprises a DON/DOFF sensor of the headset.

6. A touch pad incorporating the apparatus of claim 1.

7. A touch activated apparatus, comprising:

an electrode;

a sensor coupled to the electrode and operative to detect a change in parasitic capacitance caused by a change in proximity of a body to the electrode; and

wherein a weakly conductive material interposed between the electrode and the body.

8. The apparatus of claim 7, wherein:

the electrode comprises an earpiece of a communications headset; and

,

the apparatus comprises a DON/DOFF sensor of the headset.

9. A touch pad incorporating the apparatus of claim 7.

10. A method for improving the sensitivity of a touch activated control of a type that includes an electrode and a sensor coupled to the electrode and operative to detect a change in parasitic capacitance caused by a change in the proximity of a body to the electrode, the method comprising disposing a layer of a weakly conductive material between the electrode and the body, the layer being arranged so as to be contacted by the body.

11. A communications headset having a DON/DOFF sensor, comprising:

an earpiece comprising an electrode;

a sensor coupled to the earpiece and operative to detect a change in parasitic capacitance caused by a change in the proximity of a wearer'"'"'s ear to the earpiece; and

,

a weakly conductive covering disposed over the surface of the earpiece and arranged so as to be contacted by the wearer'"'"'s ear when the headset is donned.

12. The headset of claim 11, further comprising:

a microphone; and

,

means for holding the headset on the wearer'"'"'s head such that the earpiece is disposed in contact with the wearer'"'"'s ear and the microphone is disposed so as to receive sound from the user'"'"'s mouth.

13. The headset of claim 11, further comprising:

means for activating a circuit in response to a detection of the headset being donned; and

,

means for deactivating the circuit in response to a detection of the headset being doffed.

14. The headset of claim 11, wherein the weakly conductive covering comprises an electrostatic charge dissipative material.

15. The headset of claim 11, wherein the weakly conductive covering comprises a thermoplastic polyolefin elastomer (TEO) having a volume resistivity of from about 1.0E3 to about 9.9E9 ohm.cm.

16. The headset of claim 11, wherein the weakly conductive covering comprises an elastomer containing particles of an electrically conductive material.

17. A touch activated control, comprising:

a pad made of a weakly conductive material

an electrode disposed on a lower surface of the pad;

a sensor coupled to the electrode and operative to detect a change in parasitic capacitance caused by a change in the proximity of a body to the electrode; and

,

means for activating a circuit in response to an upper surface of the pad being contacted by the body.

18. The control of claim 17, further comprising means for deactivating the circuit in response to a loss of contact between the upper surface of the pad and the body.

19. The control of claim 18, wherein the electrode covering comprises an electrostatic charge dissipative material, a thermoplastic polyolefin elastomer (TEO) having a volume resistivity of from about 1.0E3 to about 9.9E9 ohm.cm, or an elastomer containing particles of an electrically conductive material.

20. The control of claim 17, wherein the apparatus comprises a DON/DOFF sensor of a communications headset.