Capacitive Touch Switch Layout for Invisible Backlit Appliance Controls
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Solution Overview
Problem
Existing capacitive touch switches for domestic appliances face challenges such as increased physical dimensions and complexity due to opaque walls or light guides, high costs from transparent conductive electrodes, and complex mounting processes, which hinder a clean and modern design with invisible buttons.
Innovation Solution
A capacitive touch switch with an embedded planar light guide and non-conductive transparent paint under a transparent cover, using a single side PCB with capacitive electrodes and LEDs for feedback, reduces dimensions, simplifies mounting, and eliminates the need for transparent electrodes and mechanical supports, allowing for versatile and invisible button designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If opaque walls or light guide means are used to convey light flux from light source to touch sensitive switch surfaces, then optical interference between adjacent touch switches is avoided, but physical dimensions increase and mounting complexity increases
Solution Approach 1:
The patent merges the light guide function with the control board structure by integrating light guide channels directly into the PCB layers. The light guide means are formed as integral parts of the control board using transparent or translucent materials, eliminating the need for separate opaque walls and complex mounting structures. This integration maintains optical isolation while simplifying the overall device architecture.
Solution Approach 2:
The control board is designed to serve multiple functions simultaneously: it provides structural support, electrical connections through traces, and optical guidance through integrated light guide channels. The same PCB structure that routes electrical signals also guides light flux to the appropriate touch sensitive areas, reducing the need for additional dedicated components.
2Reliability
If transparent conductive material electrodes are used between light guide and transparent cover, then electrical connection is achieved, but overall cost of control panel increases
Solution Approach 1:
The patent replaces expensive transparent conductive materials like indium tin oxide with conventional, cost-effective conductive materials such as copper or aluminum traces deposited on the PCB. These standard conductive materials achieve the same electrical connection function without the high cost associated with transparent conductive coatings, making the control panel more economically viable.
Solution Approach 2:
The invention substitutes the need for separate mechanical electrode structures with integrated electrical traces on the PCB. Instead of using distinct conductive elements positioned between the light guide and cover, the electrical connections are achieved through the PCB's existing trace network, simplifying both manufacturing and assembly.
3Strength
If springs or conductive rubber elements are used to assure mechanical connection between touch switch and transparent cover, then mechanical contact is achieved, but overall cost and complexity of single touch switch increases
Solution Approach 1:
The patent combines the mechanical support function with the electrical connection function by using the PCB itself as both the structural support and the electrical conductor. The rigid PCB provides the necessary mechanical strength to maintain contact between the touch sensitive areas and the transparent cover, while simultaneously providing the electrical traces for signal transmission, eliminating the need for separate springs or conductive rubber elements.
Solution Approach 2:
The control board is designed to serve itself by providing both mechanical support and electrical connection through its own structure. The PCB's rigid nature and integrated trace network allow it to fulfill multiple functions that would traditionally require separate components, reducing overall touch switch complexity and improving reliability.
4Object-affected harmful factors
If support member carrying electronic components is separated from transparent cover by opaque septum-like partitions, then physically delimited illumination channels are created, but device becomes bulky and manufacturing becomes complex
Solution Approach 1:
The patent extracts the light guidance function from separate opaque partition structures and integrates it directly into the control board's internal layers. By removing the need for external septum-like partitions, the design achieves light isolation through the PCB's own structure, significantly reducing the overall device volume and simplifying manufacturing while maintaining effective illumination channel delimitation.
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 achieves a reduction in physical dimensions, improved sensitivity, and cost-effectiveness while providing direct user feedback and a clean, modern design for domestic appliances, including glass ceramic surfaces and integrated oven doors.
Implementation Method 1
a capacitive electrode (8) on the lower surface of the PCB (7)
Implementation Method 2
Light generated by led 9 is conveyed inside the light guide
Data Source
Figure 1~3
Figure 4~6
AI summary
A capacitive touch switch comprises a printed circuit board and capacitive electrode provided on a surface of the printed circuit board. The printed circuit board is interposed between a transparent planar light guide and the electrode, the planar light guide being attached to a first face of a transparent cover whose second face is adapted to be touched by the user, a light source being connected to the printed circuit board and being able to convey light to the planar light guide.