Capacitive Electrode Coupling for Contoured Housing Touch Sensing

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Attaching contoured capacitive touch surfaces to flat printed circuit boards (PCBs) is challenging due to ergonomic design and the introduction of parasitic capacitance from long cables, which can vary with mechanical stress and vibration.

Innovation Solution

The capacitive sensing electrode is integrated into the housing and capacitively coupled to a sensing circuit, eliminating direct electrical connections and reducing parasitic capacitance by using connecting electrodes within the housing, allowing for reliable capacitance measurement without conductive connections through deformable materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If contoured touch surfaces are directly attached to flat PCBs, then ergonomic design is improved, but manufacturing difficulty increases and parasitic capacitance is introduced

Engineering Contradiction:

Improveergonomic designVSAvoidattachment difficulty

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The system separates the sensing electrode from the PCB by introducing an intermediate coupling circuit board. The sensing electrode is attached to the contoured surface, while the coupling circuit board provides the electrical connection interface, dividing the attachment problem into manageable segments that can be independently optimized for ergonomics and manufacturing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A coupling circuit board acts as an intermediary component between the contoured sensing electrode and the flat PCB. This mediator enables the connection of non-planar surfaces while minimizing parasitic capacitance through direct mounting, solving both the ergonomic design requirement and the manufacturing challenge.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If long cables are used to connect sensing electrodes, then flexibility is improved, but parasitic capacitance increases and measurement precision deteriorates

Engineering Contradiction:

Improveconnection flexibilityVSAvoidcapacitance measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The harmful element (long cables with high parasitic capacitance) is extracted from the system. Instead of using cables to connect the sensing electrode to the PCB, the electrode is directly mounted on the coupling circuit board, eliminating the source of parasitic capacitance while maintaining connection flexibility through the board's design.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The coupling circuit board serves as an intermediary that provides electrical connection without requiring long cables. By mounting the sensing electrode directly on the board and using short traces for connection, the system achieves both flexibility and low parasitic capacitance, preserving measurement precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If sensing electrodes are galvanically connected to PCBs, then electrical connection is simplified, but parasitic capacitance from cables and connectors increases

Engineering Contradiction:

Improveconnection simplicityVSAvoidmeasurement consistency

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The parasitic capacitance introduced by cables and connectors is extracted from the signal path. The sensing electrode is connected directly to the coupling circuit board without intermediate cables or bulky connectors, removing the source of variable parasitic capacitance and improving measurement consistency.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The mechanical connection system (cables and connectors) is replaced with a direct mounting approach on the coupling circuit board. This substitution eliminates the mechanical interfaces that introduce parasitic capacitance, providing both simplicity and reliability in the electrical connection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution enables reliable and consistent capacitance measurement, reducing the impact of mechanical stress and vibration, and allows for the use of deformable materials in capacitive sensing applications, improving the accuracy and durability of capacitive touch systems.

Implementation Method 1

The capacitive sensing circuit is configured to determine a first capacitance between the first port and a ground. The first capacitance includes a variable capacitance between the connecting electrode and a person when the person is touching the housing.

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

Capacitive coupling for connection of remotely placed capacitive sensing electrodes

Methodology Applied

Scientific EffectCapacitive coupling:

Data Source

PatentUS11863173B2Capacitive coupling for connection of remotely placed capacitive sensing electrodes

Publication Date: 2024.01.02 TEXAS INSTRUMENTS INC

AI summary

A system includes a housing, a sensing electrode disposed within the housing, and a connecting electrode. The system also includes a capacitive sensing circuit galvanically connected to the connecting electrode at a first port, but not to the sensing electrode. The capacitive sensing circuit is configured to determine a first capacitance between the first port and a ground. The first capacitance includes a variable capacitance between the connecting electrode and a person when the person is touching the housing.