Capacitive Keypad Sensing Using Crosstalk-Triggered Electrode Scanning
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Solution Overview
Problem
Conventional capacitive touch button keypad systems face challenges in accurately and efficiently capturing keypad inputs due to high computational requirements and power consumption, especially when dealing with multiple capacitor electrodes, which introduces measurement inaccuracies due to fabrication and environmental variations.
Innovation Solution
The implementation of a global sense electrode that is periodically scanned to detect touch events, initiating sequential scanning of keypad electrodes only when a touch is detected, and collecting baseline reference voltages to improve accuracy and reduce power consumption by eliminating the need to scan all electrodes at every interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all keypad electrodes are scanned at every periodic interval to ensure accurate touch detection, then measurement precision is improved, but power consumption and computational requirements increase significantly
Solution Approach 1:
The patent segments the electrode scanning process into two distinct modes: a first sensing cycle that scans a subset of electrodes (including the global sense electrode) at periodic intervals, and a second sensing cycle that scans remaining electrodes only when triggered. This segmentation allows the system to reduce power consumption by scanning fewer electrodes at full frequency while maintaining detection accuracy through selective triggering of comprehensive scans.
Solution Approach 2:
The patent implements periodic scanning with variable intensity by alternating between a first sensing cycle (scanning subset of electrodes) and a second sensing cycle (scanning all electrodes). The system periodically switches between these modes based on trigger conditions, creating a periodic action pattern that optimizes both power consumption and detection accuracy by adjusting scan frequency dynamically.
2Measurement precision
If all keypad electrodes are scanned at every periodic interval to ensure accurate touch detection, then measurement precision is improved, but computational requirements increase significantly
Solution Approach 1:
The patent segments the computational workload by dividing electrode scanning into two phases: light scanning of a subset of electrodes during the first sensing cycle, and intensive scanning of all electrodes only during the second sensing cycle when triggered. This segmentation reduces overall computational requirements by avoiding redundant full-scans while maintaining detection capability through selective triggering.
Solution Approach 2:
The patent applies partial action by scanning only a subset of electrodes (including the global sense electrode) during the first sensing cycle rather than scanning all electrodes continuously. This partial scanning approach reduces computational requirements while maintaining adequate detection performance, with full scanning reserved for triggered events when accuracy is critically needed.
3Adaptability or versatility
If multiple capacitor electrodes are used to capture keypad inputs, then sensing capability is improved, but measurement accuracy deteriorates due to fabrication and environmental variations
Solution Approach 1:
The patent introduces a global sense electrode as an intermediary element that surrounds multiple keypad electrodes. This global sense electrode acts as a mediator to detect touch events by sensing changes in the electrical field caused by finger proximity or contact, thereby providing a reference measurement that helps compensate for fabrication variations and environmental factors affecting individual electrode measurements.
Solution Approach 2:
The global sense electrode serves multiple functions: it detects touch events across the entire keypad area, provides a reference for comparing individual electrode measurements, and triggers comprehensive scanning when needed. This multi-functional approach allows the system to maintain measurement accuracy across multiple electrodes while compensating for variations through the universal reference provided by the global sense electrode.
4Speed
If continuous scanning of all electrodes is performed to detect touch events promptly, then response speed is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic scanning with variable intensity by alternating between a first sensing cycle (scanning subset of electrodes) and a second sensing cycle (scanning all electrodes). The system periodically switches between these modes based on trigger conditions, creating a periodic action pattern that optimizes both response speed and power consumption by adjusting scan frequency dynamically.
Solution Approach 2:
The patent applies preliminary action by continuously monitoring a subset of electrodes (including the global sense electrode) at periodic intervals to detect touch events before initiating comprehensive scanning. This preliminary monitoring allows the system to maintain prompt response capability for touch detection while consuming less power, with full scanning activated only when a touch event is detected or suspected.
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 approach reduces power consumption and computational resources by 5-10 times compared to conventional systems, while enhancing the accuracy of keypad touch event detection and reducing the impact of environmental conditions on sensor performance.
Implementation Method 1
capacitive keypads in which each keypad is configured as an electrode which functions as a capacitor plate to interact with a second 'plate' formed by the human touch or other input device to measure a touch voltage
Implementation Method 2
In operation, an electric field that is applied to electrodes below the touch panel is changed or altered in the vicinity of a detected touch because the touch capacitively couples with the electrode(s)
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A touch sensitive capacitive keypad system (300) is provided with a keypad sensing electrode (304) disposed within sensing proximity of multiple electrodes (E0-E9) and formed under a keypad touch panel having defined key areas, where the electrodes are respectively aligned with the defined key areas to facilitate touch detection at the keypad touch panel with a controller (310) that is configured to determine which of the plurality of defined key areas is being touched by detecting a predetermined signal characteristic at the keypad sensing electrode (304) before sequential scanning the plurality of capacitive key electrodes to identify which capacitive key electrode is aligned with a defined key area being touched.