PCB Touch Control Layout for Blind-Spot-Free Surface Sensing
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Solution Overview
Problem
Conventional touch-sensitive devices have 'blind spots' where touch input is not detected due to the absence of capacitive sensing elements, particularly at the perimeter and beyond the edges of the circuit board, limiting the responsive areas to only regions with installed sensors.
Innovation Solution
A touch-based control device that utilizes a structured printed circuit board with a sensing layer and control logic to detect touch inputs across the entire exterior panel, including regions without capacitive sensors, by selectively exposing the reference plane to enhance the electric field overlay and adjust sensitivity based on location, allowing for 'touch-anywhere' functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If capacitive sensing elements are distributed only over specific regions of the circuit board, then manufacturing complexity is reduced and sensor placement is simplified, but blind spots are created where touch input cannot be detected
Solution Approach 1:
The patent merges the reference plane (grounding layer) with the sensing function by exposing it in peripheral regions. This allows the reference plane to serve dual purposes: electrical grounding and touch sensing, eliminating blind spots without adding separate sensing elements. The exposed reference plane regions act as capacitive sensors that detect touch input in areas where traditional sensors were not placed.
Solution Approach 2:
The reference plane is given multi-functionality by exposing it in specific peripheral regions. It simultaneously serves as an electrical grounding layer and as a capacitive touch-sensing element. This universal use of the reference plane eliminates the need for additional sensing components in those regions, resolving the contradiction between manufacturing simplicity and detection coverage.
2Area of stationary object
If the sensing layer is made the same size as the reference plane, then full surface coverage is achieved, but blind spots remain in regions where no capacitive elements are present
Solution Approach 1:
The patent applies local quality by selectively exposing the reference plane only in specific peripheral regions rather than uniformly across the entire surface. Different regions have different functions: central regions have traditional capacitive sensors, while peripheral regions have exposed reference plane for sensing. This localized differentiation eliminates blind spots in critical areas without unnecessary sensing elements elsewhere.
3Ease of manufacture
If capacitive touch-sensing elements are placed only in regions with circuit board coverage, then manufacturing is simplified, but areas beyond the circuit board perimeter become non-responsive to touch
Solution Approach 1:
The patent merges the reference plane exposure with extended surface sensing capability. By exposing the reference plane at the periphery, the system combines the grounding function with touch sensing in regions that extend beyond the traditional circuit board sensing area, enabling touch detection at the very edges and corners of the device surface.
4Manufacturing precision
If sensing elements are distributed uniformly across the circuit board, then manufacturing precision requirements are reduced, but blind spots are created where antennas or other structures prevent sensor placement
Solution Approach 1:
The exposed reference plane acts as an intermediary sensing mechanism in regions where traditional capacitive sensors cannot be placed. Instead of requiring precise sensor placement in every region, the reference plane serves as a mediator that enables touch detection in antenna regions and other areas where sensor placement would interfere with other device functions.
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
Enables the detection and interpretation of touch inputs at any location on the exterior panel, including perimeter and corner regions, effectively eliminating blind spots and providing comprehensive touch sensitivity, allowing for seamless control of connected devices.
Implementation Method 1
The capacitive touch-sensing elements are reactive to changes in an electrical field that is generated over the respective element. Each sensing element of the sensing layer 510 is reactive to electric field variations that occur directly over the sensing element.
Implementation Method 2
The capacitive touch-sensing elements are reactive to changes in an electrical field that is generated over the respective element. The sensing logic can compare an input of the individual sensing elements with baseline values to detect the presence of human skin on or near the external surface 502.
Data Source
AI summary
A touch-based control device is operable to detect touch input over an entirety of the control device's exterior, including at regions of an exterior panel that (i) overlay portions of a circuit board where no touch sensors exist, and/or (ii) extend beyond a perimeter of a touch region or circuit board on which touch sensors are provided.