Capacitive and Inductive Touch Sensing for Sealed Wearable Switches
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Solution Overview
Problem
Existing wearable devices face challenges with mechanical switches due to size constraints, untidy design, risk of electric shock, and difficulty in implementing dustproofing and waterproofing, as well as distinguishing multiple touch locations on metal cases.
Innovation Solution
A touch sensing device with a cover and frame structure incorporating a touch sensing unit with a sensing electrode and inductor, and a force sensing unit with a sensing coil, which detects capacitance and inductance changes to identify touch and force inputs, allowing for seamless integration and improved safety and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mechanical switches are used in wearable devices, then switching function is achieved, but device size increases and design becomes untidy
Solution Approach 1:
The patent replaces mechanical switches with a touch sensing device that uses capacitive sensing to detect finger touches. The sensing electrode detects changes in capacitance when a finger approaches or touches the surface, eliminating the need for mechanical moving parts while maintaining the switching function. This substitution directly resolves the contradiction by removing the mechanical components that occupied space while preserving the operational capability.
2Ease of operation
If mechanical switches are used, then switching function is provided, but risk of electric shock increases
Solution Approach 1:
The touch sensing device uses capacitive coupling to detect touches without requiring direct electrical contact between the user and the switching mechanism. The sensing electrode detects capacitance changes through the insulating cover, creating an electrically isolated interface that eliminates the risk of electric shock while maintaining switching functionality.
3Ease of operation
If mechanical switches are used, then switching function is achieved, but dustproofing and waterproofing become difficult
Solution Approach 1:
The patent replaces mechanical switches with a touch-sensitive interface where the cover itself serves as the interaction surface. Since there are no mechanical moving parts, openings, or gaps required for traditional switches, the housing can be fully sealed to achieve complete dustproofing and waterproofing ratings while maintaining full switching functionality through capacitive touch detection.
4Adaptability or versatility
If multiple touch switches are disposed on metal case, then multiple touch locations are provided, but difficulty in distinguishing and recognizing locations increases
Solution Approach 1:
The patent implements multiple touch switches with distinct local characteristics by varying the sensing electrode patterns, positions, and electrical properties at different locations on the metal case. Each touch switch location has unique capacitive coupling characteristics that allow the control circuit to distinguish between different touch locations even on a conductive surface, resolving the identification difficulty while maintaining multiple functional touch points.
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
The solution enables thin, clean, and durable wearable devices with enhanced touch and force sensing capabilities, addressing size, safety, and waterproofing issues while simplifying the identification of multiple touch points.
Implementation Method 1
capacitance of the first touch sensing unit varies depending on parasitic capacitance formed between the first sensing electrode and a human body according to a contact of the human body applied through the first touch member
Implementation Method 2
inductance of the first force sensing unit varies depending on a change in distance between the first sensing coil and the frame according to a pressing touch applied through the first force member
Data Source
AI summary
A touch sensing device includes: a first touch sensing unit including a first sensing electrode and a first sensing inductor electrically connected to each other, wherein capacitance of the first touch sensing unit varies depending on parasitic capacitance formed between the first sensing electrode and a human body according to a contact of the human body; a first force sensing unit including a first sensing coil spaced apart from an internal side surface of a frame, wherein inductance of the first force sensing unit varies depending on a change in distance between the first sensing coil and the frame according to a pressing touch; and a circuit unit configured to detect whether a touch of the human body is input, based on variations in the capacitance of the first touch sensing unit and variations in the inductance with the force sensing unit.