Capacitive Sensor Switch Using Optical Correlation Against False Triggers
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Solution Overview
Problem
Capacitive sensor switches face false triggering issues due to electrically conductive liquids, which are not distinguishable from human presence, leading to inaccurate detection.
Innovation Solution
Integration of a capacitive proximity sensor with an optical sensor and an evaluation circuit that correlates capacitive and optical signals to differentiate between human presence and conductive liquids, using a dynamic threshold to enhance detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor is used to detect human presence, then detection sensitivity is improved, but false triggering by conductive liquids occurs
Solution Approach 1:
The patent combines a capacitive sensor and an optical sensor into a single detection system. The capacitive sensor detects changes in capacitance caused by conductive objects (both human presence and conductive liquids), while the optical sensor detects light absorption properties. By merging these two sensors and evaluating their signals together, the system achieves both high detection sensitivity and immunity to false triggering from conductive liquids.
Solution Approach 2:
The optical sensor acts as an intermediary that provides additional information about the detected object. When the capacitive sensor detects a conductive object, the optical sensor measures whether the object absorbs light (indicating human presence) or transmits light (indicating conductive liquid). This intermediary measurement allows the system to distinguish between true targets and false triggers.
2Device complexity
If only capacitive sensing is used, then device complexity is reduced, but detection accuracy decreases due to inability to distinguish between human presence and conductive liquids
Solution Approach 1:
The patent merges a capacitive sensor and an optical sensor into an integrated detection system with a unified evaluation circuit. This combination maintains relatively simple device architecture while significantly improving detection accuracy by enabling the system to distinguish between human presence and conductive liquids through correlated signal analysis.
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 against false triggering by accurately distinguishing between human presence and conductive liquids, ensuring reliable detection even in the presence of water or other conductive substances.
Implementation Method 1
the capacitive proximity sensor comprises a sensor conductor or sensor electrode which normally is a plate or foil of an electrically conductive material forming the active sensor surface... the evaluation circuit for evaluation and/or measurement of the capacitance to ground
Implementation Method 2
The optical sensor comprises at least one photosensor, like a photodiode... the photodiode will detect ambient light which may vary depending on the environmental conditions
Data Source
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AI summary
A sensor switch with water suppression comprises a sensor electrode and a photodiode connected to an evaluation circuit. The evaluation circuit generates a capacitive sensor signal indicative of an electrically conductive object in the proximity of the sensor switch and an optical sensor signal indicative of an object impermeable to light in the proximity of the sensor switch. The capacitive sensor signal and the optical sensor signal are correlated to generate an output signal.