Capacitive Touch Switch Thresholding for Accurate Adjacent Key Detection
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Solution Overview
Problem
Conventional capacitance type touch switch apparatuses struggle to accurately determine which touch switch among multiple adjacent switches has been activated due to low threshold settings, leading to erroneous detection of touch operations on adjacent switches when wearing gloves or in cold climates.
Innovation Solution
A capacitance type input apparatus using a determining unit that employs multiple thresholds (at least three) to differentiate the capacitance levels among touch switches, allowing precise identification of the activated switch by comparing outputs against a first, second, and third threshold, thereby enhancing detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low threshold is set for touch detection, then the sensitivity to touch operations is improved, but false detection on adjacent touch switches occurs
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the threshold value based on the detection state. When no touch is detected, a first (lower) threshold is used for high sensitivity. When a touch is detected, a second (higher) threshold is applied to distinguish the touched switch from adjacent switches, preventing false detections while maintaining initial sensitivity.
Solution Approach 2:
The threshold value is made dynamic rather than static. The system transitions between two threshold states: a lower threshold for initial touch detection and a higher threshold for confirming the specific touched switch. This dynamic adjustment resolves the contradiction between sensitivity and accuracy by adapting the threshold to the detection phase.
2Reliability
If a high threshold is set for touch detection, then false detection on adjacent touch switches is reduced, but sensitivity to actual touch operations decreases
Solution Approach 1:
The system performs preliminary detection using a lower first threshold to identify when a touch operation has occurred. Only after this preliminary detection confirms a touch event does the system switch to the higher second threshold for precise switch identification. This preliminary action ensures no touch is missed while preparing for accurate localization.
Solution Approach 2:
The threshold transitions dynamically from a lower value for initial detection to a higher value for precise identification. This time-dependent threshold adjustment ensures high sensitivity during the initial detection phase and high accuracy during the identification phase, resolving the contradiction between sensitivity and reliability.
3Device complexity
If a single threshold is used for touch detection, then the device complexity is reduced, but the ability to distinguish adjacent touch switches deteriorates
Solution Approach 1:
Instead of using multiple static thresholds simultaneously, the patent employs a dynamic threshold that switches between two values based on the detection state. This approach maintains relatively simple device architecture while achieving the differentiation capability of multiple thresholds through time-dependent parameter adjustment.
Solution Approach 2:
The system changes the threshold parameter from a single static value to a dynamically adjustable value with two distinct states. This parameter change enables the system to achieve both simple device complexity and high touch switch differentiation capability by adapting the threshold value to the specific detection phase.
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
The use of multiple thresholds enables accurate determination of the touch switch being operated, reducing false positives and improving sensitivity, especially in conditions where capacitance values are low, such as when wearing gloves.
Implementation Method 1
capacitance type input apparatus including a plurality of touch switches... comparing a first threshold used for determining whether the touch operation has been performed, with each of the outputs of the plurality of touch switches
Data Source
AI summary
A capacitance type input apparatus includes a plurality of touch switches; and a determining unit configured to determine which one touch switch among the plurality of touch switches a touch operation is performed on, based on outputs of the plurality of touch switches. The determining unit performs a first comparison of comparing a first threshold used for determining whether the touch operation has been performed, with each of the outputs of the plurality of touch switches, performs a second comparison of comparing an output that is higher than the first threshold among the outputs of the plurality of touch switches, with a plurality of comparison thresholds that are greater than first threshold and that are different from each other, and determines which one touch switch among the plurality of touch switches the touch operation is performed on, based on a comparison result of the first or second comparison.