Capacitive touch sensor
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Solution Overview
Problem
Capacitive touch sensors face challenges in accurately detecting multiple touches due to 'ghosting' and misplaced location sensing, and struggle with high production costs and complexity, especially when implementing a wide sensing area.
Innovation Solution
A capacitive touch sensor utilizing a support layer with electrically resistive threadlike elements, such as woven or knitted fabric, where each element is connected to a detection device to evaluate capacitance changes, allowing for multi-touch detection without 'ghosting' and featuring a low-cost, versatile design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Mutual Capacitance Sensing technique is used to solve ghosting problem, then multi-touch detection accuracy is improved, but device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The capacitive sensing surface is divided into multiple independent sensing zones, each with its own readout circuit. This segmentation allows each zone to independently detect touches without interference from other zones, eliminating ghosting while reducing the complexity of any single sensing unit.
Solution Approach 2:
A shield layer is introduced as an intermediary between the sensing electrodes and the environment. This shield layer reduces parasitic capacitance and electromagnetic interference, enabling accurate multi-touch detection with simpler sensing circuits.
2Area of stationary object
If capacitive grid with great number of sensing wires is implemented to achieve wide sensing area, then sensing area is increased, but manufacturing challenge and cost increase
Solution Approach 1:
The large capacitive grid is divided into multiple smaller, independent sensing zones that can be manufactured separately and then assembled together. This reduces the manufacturing complexity of each individual zone while achieving a large total sensing area through modular assembly.
Solution Approach 2:
The sensing zones are designed with universal interfaces and standardized structures that can be replicated across multiple units. This universality enables efficient manufacturing through repetition and simplifies the assembly process for creating large-area sensors.
3Measurement precision
If Mutual Capacitance Sensing is implemented, then multi-touch detection capability is improved, but frequency clock requirements and measurement accuracy demands increase
Solution Approach 1:
By dividing the sensing area into independent zones with dedicated readout circuits, each zone can operate at lower frequencies while maintaining overall high measurement accuracy. This segmentation reduces the total bandwidth requirements and lowers clock frequency demands.
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 accurate multi-touch detection without 'ghosting' and misplaced location issues, while being cost-effective and suitable for integration into various support layers, including fabrics, with improved bio-compatibility and washability.
Implementation Method 1
the controller is configured to detect the change of value in the capacitance of each sensing wire due to the parasitic capacitance provided by an object (e.g. a finger) touching the sensing wire
Data Source
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AI summary
It is disclosed a capacitive touch sensor (10) comprising a support layer (1) having a plurality of sensing threadlike elements (2) coupled thereto and configured to be electrically connected to a detection device (5) for evaluating the capacitance value (C) of each sensing threadlike element (2) of said plurality of sensing threadlike elements, characterized in that said sensing threadlike elements (2) comprise a plurality of electrically resistive threadlike elements (2r), wherein the electrical resistance per unit of length of each electrically resistive threadlike element (2r) is comprised between 10 kQ/m and 10 MΩ/m. An article comprising the capacitive touch sensor (10) and a method for detecting a touch event on a support layer (1) are also disclosed.