Capacitive Touch Sensor Assembly With Flexible Overlay for Wet Use
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Solution Overview
Problem
Capacitive touch sensors in harsh and wet environments tend to register false readings due to water contamination and can be overly sensitive, making them difficult for users to operate effectively, as they are calibrated to avoid false positives.
Innovation Solution
A capacitive touch sensor assembly with a flexible layer overlaying the sensor element, creating a pocket with a compressible medium, which allows for easier activation and maintains functionality even with water presence, using a control circuit responsive to capacitance changes between the sensor element and flexible layer to generate appropriate output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the capacitive sensor is calibrated to a more precise range of capacitance change to avoid false positives from water, then false sensor readings from water contamination are reduced, but the sensor becomes overly sensitive and some users cannot trigger the switch
Solution Approach 1:
A flexible overlay layer is introduced as an intermediary between the user's finger and the capacitive sensor. This layer physically separates the sensor from water contamination while still allowing capacitive coupling for user interaction. The overlay acts as a mediator that blocks water from reaching the sensor active region while maintaining the electrical field necessary for touch detection, thus resolving the contradiction between measurement precision and ease of operation.
2Ease of operation
If the capacitive sensor is placed in a wet environment for user accessibility, then user accessibility is improved, but water enters the active region causing false sensor readings
Solution Approach 1:
A flexible overlay layer (thin film) is placed over the capacitive sensor to protect it from water contamination. This flexible shell allows the sensor to remain accessible to users in wet environments while preventing water from directly contacting the sensor's active region. The flexible nature of the overlay maintains touch sensitivity while providing environmental protection.
3Reliability
If membrane switches are used in harsh environments, then durability is improved, but they are prone to degradation over time leading to product failure
Solution Approach 1:
The patent replaces mechanical membrane switches with capacitive sensors. Capacitive sensors have no moving parts or mechanical components that can wear out, unlike membrane switches that degrade over time due to physical stress and environmental exposure. This substitution eliminates the mechanical degradation issue while maintaining durability and reliability in harsh environments.
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 prevents false sensor readings from water contamination while allowing all users to operate the sensor assembly, regardless of their size or conductance, by reducing the required activation force and maintaining functionality in wet conditions.
Implementation Method 1
a sensor element that generates an electric field having an active region
Implementation Method 2
a pocket is established between the flexible layer and sensor element. This pocket, in turn, can include a compressible medium, such as air, to allow the flexible layer over the sensor element to be depressed by a user
Data Source
AI summary
A controller for use in a wet environment, such as a controller for a pool or spa, includes a sensor element that generates an electric field having an active region. For the controller, at least one flexible layer is positioned to overlay the sensor element and surround the active region. With this arrangement, a pocket is established between the flexible layer and sensor element. A control circuit that is responsive to the capacitance between the sensor element and the flexible layer is provided. When the flexible layer is deformed, the capacitance changes and the control circuit generates an output signal that corresponds to a particular switch state for a connected device (e.g. pump or heater). For the controller, the control circuit is designed and/or calibrated to maintain a current switch state output in response to the presence of water on the controller and near the active region.