Capacitive Button Sense Element Configuration for Touch Differentiation
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Solution Overview
Problem
Conventional capacitive sensing systems struggle to effectively differentiate between touches from different size conductive objects, such as human fingers and stylus, leading to false touches and reduced immunity to external noises due to the need for high sensitivity settings.
Innovation Solution
The implementation of a capacitive button with a dual or triple sense element configuration, where the inner perimeter of one sense element surrounds the outer perimeter of another, allowing for dynamic adjustment of sensing parameters to distinguish between larger and smaller conductive objects by measuring self-capacitance or mutual capacitance, thereby avoiding excessive sensitivity and false touches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high sensitivity settings are used to detect small conductive objects like stylus, then detection capability for small objects is improved, but false touches from large objects like fingers increase
Solution Approach 1:
The capacitive button is divided into multiple sense elements with different sensing parameters. The first sense element has parameters optimized for detecting small conductive objects (stylus), while the second sense element has parameters optimized for detecting large conductive objects (fingers). This segmentation allows each sense element to specialize in detecting a specific object size, resolving the contradiction between detecting small objects without causing false touches from large objects.
Solution Approach 2:
Different regions of the capacitive button have different sensing characteristics. The first sense element is configured with high sensitivity for small objects, while the second sense element is configured with lower sensitivity but larger detection area for small objects. This local quality differentiation allows the system to optimize detection for different object types in different spatial zones, eliminating the need for uniform high sensitivity that causes false touches.
2Adaptability or versatility
If single sense element configuration is used, then device complexity is reduced, but ability to differentiate object sizes is lost
Solution Approach 1:
The sense elements are arranged in a nested configuration where the second sense element is positioned within or around the first sense element. This nested structure allows both sense elements to coexist in a compact arrangement, providing multi-size object differentiation capability without significantly increasing the overall device footprint or complexity.
Solution Approach 2:
The capacitive button with multiple sense elements serves multiple functions: it can detect both small and large conductive objects, differentiate between object sizes, and provide comprehensive coverage for various touch scenarios. This multi-functionality is achieved through a relatively simple dual sense element configuration, making the system versatile without proportionally increasing complexity.
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
This configuration enables accurate detection and differentiation of touches from various sizes of fingers and stylus without making the sense element overly sensitive, reducing false touches and improving immunity to external noise, while maintaining seamless user interface performance.
Implementation Method 1
capacitance sensing circuits operative to measure signals from a first sense element and a second sense element of a capacitive button... The signals correspond to capacitances of the first sense element and second sense element
Data Source
AI summary
Apparatuses and methods of distinguishing between a finger and stylus proximate to a touch surface are described. One apparatus includes a first circuit to obtain capacitance measurements of sense elements when a conductive object is proximate to a touch surface. The apparatus also includes a second circuit coupled to the first circuit. The second circuit is operable to detect whether the conductive object activates the first sense element, second sense element, or both, in view of the capacitance measurements. To distinguish between a stylus and a finger as the conductive object, the second circuit determines the conductive object as being the stylus when the second sense element is activated and the first sense element is not activated and determines the conductive object as being the finger when the first sense element and the second sense element are activated.