Capacitive Pressure Sensing Pad Layout for Touch-Press Separation
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Solution Overview
Problem
Conventional capacitive keyboards face challenges in accurately distinguishing between touch and press events due to limited signal differentiation, leading to erroneous detection and noise interference.
Innovation Solution
A pressure sensing unit with a pressure sensing pad group including a first and second pressure sensing pad electrically shielded by a ground pad, combined with a floating conductive element that overlaps and moves relative to the pad group, enhances signal-to-noise ratio by measuring variations in equivalent capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitive sensing circuit with sensor electrodes is used, then the keyboard can detect touch events, but the capacitance value changes are too small to reliably distinguish between touch and press events
Solution Approach 1:
The sensing system is segmented into multiple independent sensing points, each with its own sensor electrode pair. This allows individual optimization of each sensing point and enables spatial differentiation of touch events across the keyboard surface, improving overall detection reliability
Solution Approach 2:
The patent transitions from detecting only capacitance value changes to detecting both capacitance changes and impedance changes. By adding the impedance detection dimension, the system can better distinguish between touch and press events, as impedance varies differently than capacitance during these events
2Device complexity
If the keyboard uses a simple capacitive sensing system, then the device complexity is low, but noise interference makes it difficult to determine whether a key is pressed or only touched
Solution Approach 1:
The patent introduces a chip as an intermediary component that receives sensing signals from multiple sensor electrodes, processes the capacitance and impedance data, and generates appropriate codes. This intermediary performs signal filtering, noise reduction, and event classification, significantly improving detection reliability without requiring complex hardware at the sensor level
Solution Approach 2:
The patent replaces traditional mechanical switch mechanisms with a capacitive sensing system that uses electrical field changes to detect key events. This substitution eliminates mechanical wear and noise while maintaining detection capability through electrical measurements of capacitance and impedance
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 improves the accuracy of press signal detection, reducing noise interference and preventing erroneous inputs by amplifying the press signal-to-noise ratio.
Implementation Method 1
one of the floating conductive element and the pressure sensing pad group is configured to be movable in a movement direction relative to another one of the floating conductive element and the pressure sensing pad group. The floating conductive element overlaps with the pressure sensing pad group in the movement direction.
Data Source
AI summary
A pressure sensing unit, a capacitive hybrid sensor device, and an input apparatus using the same are provided. The pressure sensing unit for detecting pressing events includes a pressure sensing pad group and a floating conductive element. The pressure sensing pad group includes a first pressure sensing pad, a second pressure sensing pad, and a ground pad that are spaced apart from one another. The first and second pressure sensing pads are electrically shielded from each other by the ground pad. One among the floating conductive element and the pressure sensing pad group is configured to be movable in a movement direction relative to another one among the floating conductive element and the pressure sensing pad group. The floating conductive element overlaps with the pressure sensing pad group in the movement direction. Therefore, a signal-to-noise ratio can be increased and an erroneous detection can be prevented.