Method and apparatus for sensing the force with which a button is pressed

• US 20070227256A1
• Filed: 03/31/2006
• Published: 10/04/2007
• Est. Priority Date: 03/31/2006
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Wright, David
• Granted Patent: US 7,721,609 B2
• Time in Patent Office: Days
• US Class Current: 73/780
• CPC Class Codes: A63F 13/218 using pressure sensors, e.g. generating a signal proportional to the pressure applied by the player
• CPC Class Codes: A63F 13/24 Constructional details thereof, e.g. game controllers with detachable joystick handles
• CPC Class Codes: A63F 2300/1043 being characterized by constructional details
• CPC Class Codes: A63F 2300/1056 involving pressure sensitive buttons
• CPC Class Codes: G01L 1/142 using capacitors
• CPC Class Codes: G01L 5/223 to joystick controls
• CPC Class Codes: G05G 2009/04762 Force transducer, e.g. strain gauge
• CPC Class Codes: H03K 17/975 using a capacitive movable element

Abstract

Disclosed is an apparatus for sensing a force, comprising an actuator having a conductive deformable surface, a substrate having a first conductive trace and a second conductive trace, a housing coupled to the actuator and to the substrate, holding the actuator in proximity to the substrate, and a circuit for measuring a capacitance value.

Claims

1. An apparatus for sensing a force, comprising:

an actuator having a conductive deformable surface;

a substrate having a first conductive trace and a second conductive trace;

a housing coupled to the actuator and to the substrate, holding the actuator in proximity to the substrate; and

a circuit for measuring a capacitance value.

2. The apparatus of claim 1, wherein a force applied to the actuator moves the actuator in a perpendicular manner towards the conductive traces of the substrate, causing the deformable surface to deform and increase a surface area in proximity to the conductive trace on the substrate, where the capacitance between the actuator and one or both of the traces increases as increasing force is applied to the actuator.

3. The apparatus of claim 2, wherein the first conductive trace is located approximately below a center axis of the actuator, and the second conductive trace is located around the first capacitive trace.

4. The apparatus of claim 3, where the first conductive trace is coupled to ground, and the second conductive trace is covered with solder resist.

5. The apparatus of claim 2, wherein the first conductive trace and second conductive trace are both located approximately below a center axis of the actuator, and both the first and second conductive traces are covered by solder resist.

6. The apparatus of claim 5, wherein the first conductive trace is coupled to ground.

7. The apparatus of claim 2, wherein the first conductive trace and second conductive trace are both located approximately below a center axis of the actuator, and a third conductive trace is also located approximately below a center axis of the actuator.

8. The apparatus of claim 7, wherein the first conductive trace is covered by solder resist, the second conductive trace is coupled to a logic signal, and the third conductive trace is coupled to ground.

9. The apparatus of claim 1 wherein the actuating surface makes an electrical contact between a plurality of conductive traces, and forms a capacitor between those traces and other traces from which the actuating surface is electrically insulated.

10. The apparatus of claim 9 in which an electrical circuit is used to detect said electrical contact between said un-insulated circuit board traces.

11. The apparatus of claim 1 in which the circuit for measuring capacitance comprises a relaxation oscillator.

12. The apparatus of claim 1 further comprising a processing element configured to calculate the force of actuation from the magnitude of the capacitance measured.

13. The apparatus of claim 12 further comprising a communication means between the processing element and a computer system.

14. A method for determining the force with which an actuator is pressed comprising:

providing an actuator with a conductive actuating surface which deforms when pressed against a flat surface, where the area of the conductive surface in contact with the flat surface increases as the actuating force increases;

providing a circuit board with conductive traces having an insulating material over the traces, such that a capacitance is created between said traces that varies as the actuating surface is pressed against the insulator;

measuring a first capacitance value between the traces on the circuit board; and

providing the capacitance measurement to a processing element.

15. The method of claim 14, further comprising measuring a second capacitance value between the traces on the circuit board and computing a measure of the force of actuation from first and second capacitance values.

16. The method of claim 14, further comprising computing a measure of the force of actuation from the first capacitance values.

17. The method of claim 14 further comprising:

detecting whether the actuator is in contact with the flat surface; and

measuring the capacitance between the circuit board traces only when the actuator has been detected as being in contact with said surface.

18. The method of claim 14 further comprising communicating a measure of the force computed to a computer system.

19. The method of claim 18 further comprising:

when the actuator is detected as not being in contact with the surface, communicating this information to the computer; and

when the actuator is detected as being in contact with the surface communicating a measure of the force computed to the computer system.

20. A circuit for sensing an actuating force, comprising

a first conductive trace coupled to a reference voltage;

a second conductive trace electrically insulated from the first conductive trace, located proximate to the first conductive trace; and

a sensor having a sensing input coupled to the second conductive trace, and having an output.

21. The circuit of claim 20, wherein the output of the sensor indicates a measure of actuating force.

22. The circuit of claim 21, wherein the output of the sensor comprises one of a frequency, a voltage, a pulse width modulated signal, or a current.

23. An entertainment system, comprising:

an entertainment device configurable to provide multimedia output;

a handheld input device capable of providing user input to the console, wherein the input device is configurable to sense an actuating force using a capacitance measurement; and

a communication protocol operating between the input device and the entertainment console.

24. The system of claim 23, wherein the entertainment device is a games console.

25. The system of claim 24 wherein the communication protocol operating between the input device and the entertainment console is a wireless communication protocol.

26. The system of claim 24 wherein the communication protocol operating between the input device and the entertainment console is a wired communication protocol.

27. The system of claim 23 wherein the a handheld input device is a game controller.