Differential Sense Wire Layout for Capacitive Sensor Cross-Talk
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Solution Overview
Problem
Capacitive sensors in plumbing applications such as electronic faucets and toilets experience cross-talk and false readings due to nearby components, leading to unintended activation and inaccurate fluid control.
Innovation Solution
The implementation of a differential sensing system using a first and second sense wire configuration for capacitive sensors, where the controller processes a difference signal between the outputs from these wires to reduce cross-talk effects, allowing for accurate detection of user interactions and fluid levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive sensors are used in plumbing applications, then the sensors can detect user interactions and fluid levels, but cross-talk from nearby components and multiple sensors causes false readings and unintended activation
Solution Approach 1:
A differential amplifier is introduced as an intermediary component between the capacitive sensors and the control logic. The amplifier receives signals from multiple capacitive sensors and processes them differentially, subtracting common-mode signals (cross-talk) from the desired sensor signals. This intermediary device effectively filters out cross-talk interference while preserving genuine user interaction detections.
Solution Approach 2:
The sensing system is segmented into multiple independent capacitive sensor elements, each monitoring a specific zone. By segmenting the sensing function across multiple sensors with dedicated signal paths, the system can isolate and identify cross-talk sources more easily and apply differential processing to eliminate interference while maintaining accurate detection in each zone.
2Adaptability or versatility
If multiple capacitive sensors are coupled to the same controller, then comprehensive sensing coverage is achieved, but cross-talk between sensors causes false sensing events
Solution Approach 1:
Differential amplifiers serve as intermediary signal conditioning devices between multiple capacitive sensors and the controller. Each sensor signal path includes a differential amplifier that processes signals before they reach the controller, eliminating cross-talk at the signal level and preventing false activation while maintaining comprehensive sensing coverage.
Solution Approach 2:
Instead of trying to eliminate cross-talk by reducing sensor quantity or spacing, the system inverts the approach by using the cross-talk signals themselves as part of the differential measurement. By configuring sensors and amplifiers to detect differences between signals rather than absolute values, the system converts the harmful cross-talk into useful reference information that helps identify genuine events.
3Object-affected harmful factors
If software algorithms are used to reduce cross-talk effects, then some interference can be mitigated, but the system complexity increases
Solution Approach 1:
The patent replaces complex software-based cross-talk mitigation algorithms with a hardware-based differential amplification approach. The differential amplifiers perform cross-talk rejection through their inherent circuit architecture, eliminating the need for sophisticated software processing and reducing overall system complexity while maintaining effective cross-talk suppression.
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 effectively minimizes cross-talk interference, enhancing the accuracy of capacitive sensor readings and preventing false activations, thereby improving the reliability of electronic faucets, toilets, and soap dispensers.
Implementation Method 1
a first capacitive sensor coupled to a first component, and a second capacitive sensor coupled to a second component. The second capacitive sensor includes a sensing electrode, a first sense wire coupled to the electrode, and a second sense wire spaced apart from the electrode.
Implementation Method 2
The controller is programmed to determine a difference signal between first and second output signals received from the first and second sense wires of the second capacitive sensor, respectively, to reduce an effect of cross-talk from the first capacitive sensor on the second capacitive sensor.
Data Source
AI summary
An apparatus and method is provided to reduce cross-talk between multiple capacitive sensors used in an electronic toilet and between multiple capacitive sensors used in an electronic faucet and an electronic soap dispenser.