Dual-Electrode Capacitive Switch for Water-Insensitive Touch Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive sensor switches for touch-sensitive applications, such as cooktops, face issues with false triggering due to conductive liquids, which can lead to incorrect detection of object proximity.
Innovation Solution
A capacitive sensor switch design featuring two sensor electrodes with separate signal generators and an evaluation circuit that differentiates between signal attenuation and cross-coupling effects, allowing for precise detection of object proximity while minimizing false triggers from conductive liquids, by using high coupling impedance and alternating signal generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single sensor electrode with AC signal is used to detect object proximity, then the detection function is simple, but conductive liquid causes false triggering
Solution Approach 1:
The sensor electrode is segmented into a first sensor electrode and a second sensor electrode, each independently coupled to signal generators. This segmentation allows the system to distinguish between genuine touch signals and false triggers from conductive liquids by comparing signals from multiple electrodes, thereby improving reliability while maintaining manageable complexity.
Solution Approach 2:
The patent introduces a spatial dimension by arranging sensor electrodes in specific geometric patterns (e.g., concentric circles, intersecting lines). This dimensional arrangement enables the system to detect the spatial distribution of capacitive effects, allowing differentiation between localized finger touches and widespread water contamination.
2Reliability
If multiple sensor electrodes with separate signal generators are used, then immunity to conductive liquid is improved, but device complexity increases
Solution Approach 1:
The patent merges the functionality of multiple signal generators into a single integrated signal generator that can output multiple signals simultaneously or sequentially. This consolidation reduces the number of discrete components and simplifies the overall device architecture while maintaining the reliability benefits of multiple independently driven sensor electrodes.
Solution Approach 2:
The signal generator employs periodic alternation between driving different sensor electrodes with AC signals. By sequentially activating different electrode pairs and analyzing the responses, the system achieves water-insensitivity through time-multiplexed measurement, reducing hardware complexity while maintaining high reliability.
3Measurement precision
If high coupling impedance is used between signal generator and sensor electrode, then object detection precision is improved, but signal attenuation increases
Solution Approach 1:
The evaluation circuit incorporates feedback mechanisms that continuously monitor the AC signals from sensor electrodes and adjust measurement parameters in real-time. This feedback allows the system to compensate for signal attenuation caused by high coupling impedance, maintaining measurement precision by dynamically optimizing signal levels and detection thresholds based on actual electrode responses.
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 solution provides high immunity to false triggering from conductive liquids, enabling accurate detection of object proximity and reducing errors in sensor switch operations.
Implementation Method 1
a first signal generator capacitively coupled to the first sensor electrode, and a second signal generator capacitively coupled to the second sensor electrode. The capacitive coupling of the signal generator(s) provides a comparatively high coupling impedance between each signal generator and the associated sensor electrode
Implementation Method 2
An object approaching the first sensor electrode and the second sensor electrode at the same time may in addition to an attenuation produce a cross-coupling of the signals between the first and the second sensor electrode
Data Source
AI summary
A sensor switch including a first sensor electrode and a second sensor electrode at least partially surrounding the first sensor electrode. An evaluation and control circuit of the sensor switch is configured to generate a switch output signal if a first sensor electrode attenuation signal indicates a high signal attenuation, a second sensor electrode attenuation signal indicates a low signal attenuation, and a cross-coupling signal from the first to the second electrode indicates a low cross-coupling.