Pressure Sensing Pad Layout for Accurate Key Press Detection
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Solution Overview
Problem
Conventional capacitive touch sensitive mechanical keyboards face challenges in accurately distinguishing between key press and touch events due to limited signal differentiation, leading to erroneous detection and noise interference.
Innovation Solution
A pressure sensing unit with a capacitive hybrid sensor device featuring a pressure sensing pad group including a first and second pressure sensing pad electrically shielded by a ground pad, and a floating conductive element that overlaps with the pad group, improving signal-to-noise ratio by varying the equivalent coupling 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 key presses and touches, but the capacitance values for touched and pressed states have small differences leading to erroneous detection
Solution Approach 1:
The sensing circuit is divided into two independent parts: a first sensing circuit with first sensor electrodes for detecting touched events, and a second sensing circuit with second sensor electrodes for detecting pressed events. This segmentation allows each circuit to be optimized for its specific detection task, improving the reliability of event classification by preventing erroneous detection between touch and press states.
Solution Approach 2:
Different sensing regions are designed with different electrode configurations and electrical characteristics. The first sensing circuit uses electrode arrangements optimized for detecting proximity touches, while the second sensing circuit uses configurations optimized for detecting actual key presses. This local differentiation enables accurate discrimination between touch and press events based on the specific electrical characteristics of each region.
2Device complexity
If a single capacitive sensing circuit is used for both touch and press detection, then the device structure remains simple, but noise interference increases and signal-to-noise ratio decreases
Solution Approach 1:
The single capacitive sensing circuit is segmented into two independent sensing circuits with separate sensor electrode pairs. This segmentation isolates the detection of touch events from press events, preventing noise and signal interference between the two types of detections. Each circuit can be independently optimized and calibrated, reducing overall system noise while maintaining structural simplicity.
3Length of moving object
If the pressed distance is limited, then the mechanical structure remains compact, but the difference between capacitance values in touched and pressed states becomes smaller
Solution Approach 1:
Different electrode configurations are used in the first and second sensing circuits to create distinct electrical characteristics for touch and press detection. The second sensing circuit is specifically designed with electrode parameters that maximize capacitance change for small press distances, enabling accurate press detection even when the mechanical pressed distance is limited to maintain compact form factor.
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 enhances the accuracy of press signal detection while reducing noise interference, preventing erroneous key event registration and improving overall input apparatus performance.
Implementation Method 1
a first pressure sensing pad, a second pressure sensing pad, and a ground pad that are spaced apart from one another, and the first pressure sensing pad and the second pressure sensing pad are electrically shielded from each other by the ground pad
Implementation Method 2
A pressure sensing unit with a capacitive hybrid sensor device featuring a pressure sensing pad group including a first and second pressure sensing pad electrically shielded by a ground pad, and a floating conductive element that overlaps with the pad group, improving signal-to-noise ratio by varying the equivalent coupling capacitance
Data Source
AI summary
A pressure sensing unit is provided. The pressure sensing unit includes a membrane and a pressure sensing pad group. The membrane has a first surface and a second surface. 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 ground pad and one among the first pressure sensing pad and the second pressure sensing pad are located at the first surface of the membrane, another one among the first pressure sensing pad and the second pressure sensing pad is located at the second surface of the membrane, and an orthographic projection of the ground pad projected onto a reference plane is located between orthographic projections of the first pressure sensing pad and the second pressure sensing pad that are projected onto the reference plane. Therefore, a signal-to-noise ratio can be increased and an erroneous detection can be prevented.