Force Sensing Switch With Strain Gauges On Deflectable Beam
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Solution Overview
Problem
Existing input devices, such as switches and buttons, provide only binary input options, failing to capture the varying levels of force applied by users, which limits the range of user interactions in electronic devices.
Innovation Solution
A force sensing switch is introduced, featuring a dome switch over a deflectable beam with strain gauges to measure beam strain, allowing the processing device to determine the amount of force applied, and optionally actuating the dome switch, enabling multiple input states based on force levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dome switch is used to detect input, then the device can register when a key is pressed, but it cannot differentiate between different force levels applied to the key
Solution Approach 1:
The patent combines a dome switch with strain gauges mounted on a deflectable beam to create a hybrid input device. The dome switch provides binary actuation detection while the strain gauges measure the magnitude of applied force, merging simple mechanical switching with precise force sensing in a single integrated structure.
Solution Approach 2:
The input device serves multiple functions simultaneously: it detects whether a key is pressed (dome switch function), measures the force applied (strain gauge function), and can potentially distinguish between different input intentions based on force magnitude. This multi-functionality allows a single device to replace what would otherwise require separate components.
2Adaptability or versatility
If only binary input devices are used, then the device structure remains simple, but the range of user interactions is limited
Solution Approach 1:
The patent transitions from binary input detection to continuous force magnitude measurement by incorporating strain gauges that output analog signals proportional to the applied force. This parameter change from discrete states to continuous measurement enables a wider range of user interactions while maintaining a relatively simple mechanical structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables electronic devices to register and differentiate various force levels applied to input surfaces, enhancing user interaction capabilities beyond traditional binary inputs by providing multiple output states.
Implementation Method 1
One or more strain gauges can also be disposed over one or more surfaces of the beam. For example, a strain gauge can be placed over the top surface and the bottom surface of the beam, or four strain gauges can be disposed over the top surface of the deflectable beam. When a force is applied to the input surface, the strain gauge or gauges can measure an amount of strain in the deflectable beam.
Implementation Method 2
A dome switch is typically constructed by placing a deformable dome over a conductive contact pad on a circuit board. When a user presses down on the key, the dome collapses such that a conductive surface of the dome contacts the conductive contact pad, thereby actuating the dome switch.
Data Source
AI summary
A force sensing switch for use in an electronic device can include one or more dome switches disposed over a top surface of a deflectable beam. One or more strain gauges can be disposed over at least one surface of the deflectable beam. An electronic device that includes at least one force sensing switch can further include a processing device operatively connected to the one or more strain gauges. Alternatively or additionally, an electrode can be disposed under a bottom surface of the deflectable beam and a capacitance measured between the bottom surface and the electrode.