Touch sensor and control circuit therefor

• US 5,594,222 A
• Filed: 10/25/1994
• Issued: 01/14/1997
• Est. Priority Date: 10/25/1994
• Status: Expired due to Term

• Current Assignee: Touchsensor Technologies LLC (Methode Electronics Incorporated)
• Original Assignee: Integrated Controls
• Inventors: Caldwell, David W.
• Primary Examiner(s): Scott, J. R.
• Application Number:
  US08/328,852
• Time in Patent Office: 812 Days
• Field of Search: 200/5 A, 200/600, 361/278, 361/280, 307/116, 307/99, 341/22, 341/33, 341/26, 341/24, 345/173, 345/174, 400/479.1
• US Class Current: 200/600
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/94026 Automatic threshold calibration; e.g. threshold automatically adapts to ambient conditions or follows variation of input
• CPC Class Codes: H03K 2217/94031 Calibration involving digital processing
• CPC Class Codes: H03K 2217/960775 Emitter-receiver or "fringe" type detection, i.e. one or more field emitting electrodes and corresponding one or more receiving electrodes

Abstract

A low impedance touch sensor detects manual contact of a dielectric substrate by a human user. The touch sensor includes a first conductive electrode pad having a closed, continuous geometric form and a second conductive electrode which substantially co-planarly surrounds the first electrode and is spaced from the first electrode by a channel. The first and second electrodes are disposed on the same surface of the substrate. An active electrical component, such as a transistor is located on the substrate proximate the first and second electrodes, and is electrically coupled to the first and second electrodes.

Claims

1. A low impedance touch sensor apparatus for detecting manual contact by a human user and capable of activating a controlled device, said touch sensor apparatus comprising:

a dielectric substrate of substantially uniform thickness having first and second opposite surfaces;

a first thin, conductive electrode pad disposed on said first surface of said substrate in a closed, continuous geometric form having an area which affords substantial coverage by a human appendage;

a second thin, conductive electrode disposed on said first surface of said substrate in a spaced, coplanar and substantially surrounding relationship to said first electrode pad; and

an active electrical component disposed on said substrate proximate said first and second electrodes and electrically coupled to said first and second electrodes, such that human contact of said substrate activates the controlled device.

2. The apparatus of claim 1 wherein a strobe line is disposed on said first surface of said substrate and electrically coupled to said second electrode.

3. The apparatus of claim 2 wherein a strobe signal is applied to said strobe line, said strobe signal creating an electric field between said first and second electrodes.

4. The apparatus of claim 3 wherein said electric field has an arc-shaped path originating at said second electrode and terminating at said first electrode.

5. The apparatus of claim 1 further including a sense line disposed on said first surface of said substrate proximate said first and second electrodes.

6. The apparatus of claim 5 wherein said touch sensor generates a detection signal on said sense line indicating the status of said touch sensor.

7. The apparatus of claim 6 wherein said detection signal is received by a detection circuit, said detection circuit including a peak detector.

8. The apparatus of claim 6 wherein the level of said detection signal is altered when said substrate is touched by said appendage of said user.

9. The apparatus of claim 1 wherein said first surface of said substrate is a non-touched surface, and said second surface of said substrate is a touched surface.

10. The apparatus of claim 1 wherein said substrate is glass.

11. The apparatus of claim 1 wherein said substrate is plastic.

12. The apparatus of claim 1 wherein a channel is located between said first and second electrodes, said channel having a generally uniform width.

13. The apparatus of claim 1 wherein a plurality of said touch sensors are disposed on said first surface of said substrate.

14. The apparatus of claim 1 wherein a plurality of said touch sensors are disposed on said first surface of said substrate and arranged in a matrix of rows and columns.

15. The apparatus of claim 14 wherein a common strobe line is electrically coupled to said column of touch sensors and a common sense line is electrically coupled to said row of touch sensors.

16. A low impedance touch sensor apparatus for detecting manual contact by a human user and capable of activating a controlled device, said touch sensor apparatus comprising:

a dielectric carrier;

a first thin, conductive electrode pad disposed on said carrier in a closed, continuous geometric form having an area which affords substantial coverage by a human appendage;

a second thin, conductive electrode disposed on said carrier in a spaced and substantially surrounding relationship to said first electrode;

an active electrical component disposed on said carrier proximate said first and second electrodes and electrically coupled to said first and second electrodes; and

a dielectric substrate having first and second opposite surfaces, said dielectric carrier disposed on said first surface of said dielectric substrate, such that human contact of said substrate activates the controlled device.

17. The apparatus of claim 16 wherein said first surface of said substrate is a non-touched surface and said second surface of said substrate is a touched surface.

18. A low impedance touch sensor apparatus for detecting manual contact by a human user and capable of activating a controlled device, said touch sensor apparatus comprising:

a dielectric substrate of substantially uniform thickness having first and second opposite surfaces;

a first thin, conductive electrode pad disposed on said first surface of said substrate in a closed, continuous geometric form having an area which affords substantial coverage by a human appendage;

a second thin, conductive electrode disposed on said first surface of said substrate in a spaced, coplanar and substantially surrounding relationship to said first electrode pad; and

a transistor disposed on said first surface of said substrate proximate said first and second electrodes and electrically coupled to said first and second electrodes, such that human contact of said substrate activates the controlled device.

19. The apparatus of claim 18 wherein said transistor is a PNP transistor.

20. The apparatus of claim 18 further including a resistor disposed on said first surface of said substrate and electrically coupled between said first and second electrodes.

21. The apparatus of claim 18 further including a sense line disposed on said first surface of said substrate proximate said first and second electrodes.

22. The apparatus of claim 18 wherein said transistor has a base, a collector and an emitter, said transistor base is connected to said first electrode, said transistor collector is connected to said sense line, and said transistor emitter is connected to said second electrode.

23. The apparatus of claim 18 wherein a plurality of said touch sensors are disposed on said first surface of said substrate.

24. The apparatus of claim 21 wherein said touch sensor generates a detection signal on said sense line indicating the status of said touch sensor.

25. The apparatus of claim 24 wherein a signal level of said detection signal is altered when said substrate is touched by said appendage of said user.

26. A touch sensor apparatus including a plurality of touch pads each detecting manual contact by a human user and capable of activating a controlled device, each touch pad comprising:

a dielectric substrate of substantially uniform thickness and having first and second opposite surfaces;

a first thin, conductive electrode pad having a peripheral edge and disposed on said first surface of said substrate in a closed, continuous geometric form having an area which affords substantial coverage by a human appendage; and

a second thin, conductive electrode disposed on said first surface fo said substrate in a spaced relationship to said first electrode, said second electrode surrounding said first electrode on peripheral edges having an adjacent touch pad.

27. The apparatus of claim 26 further including a strobe line disposed on said first surface of said substrate and electrically coupled to said second electrode.

28. The apparatus of claim 27 wherein a strobe signal is applied to said strobe line to create an electric field between said first and second electrodes.

29. The apparatus of claim 28 wherein said electric field is in opposition to electric fields created by adjacent touch pads.

30. The apparatus of claim 26 further including a sense line disposed on said first surface of said substrate proximate said first and second electrodes, said touch sensor generating a detection signal on said sense line.

31. The apparatus of claim 26 wherein said first surface of said substrate is a non-touched surface and said second surface of said substrate is a touched surface.

32. A plurality of touch pads for detecting manual contact by a human user and capable of activating a controlled device, each touch pad comprising:

a dielectric carrier;

a first thin, conductive electrode pad having a peripheral edge and disposed on said carrier in a closed, continuous geometric form having an area which affords substantial coverage by a human appendage;

a second thin, conductive electrode disposed on said carrier in a spaced relationship to said first electrode, said second electrode surrounding said first electrode on peripheral edges having an adjacent touch pad; and

a dielectric substrate having first and second opposite surfaces, said carrier disposed on said first surface of said substrate, such that human contact of said substrate activates the controlled device.