Capacitive Incremental Encoder for Direction and Step Detection

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Solution Overview

Problem

Existing capacitive incremental encoders are not cost-effective and lack efficient methods to determine actuation direction and number of steps without mechanical displacement, and are prone to incorrect operation due to contamination.

Innovation Solution

A capacitive incremental encoder design where each group of sensor surfaces is electrically conductively connected to a voltage source and an evaluation circuit, allowing for determination of actuation direction and number of steps through changes in output signals, with periodic signal threshold triggering and active shielding to minimize interference, and using a clock signal for efficient capacitance querying.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If capacitive sensors are arranged in groups with electrically insulating cover plates, then user safety and sensor protection are improved, but the complexity of determining actuation direction and step count increases

Engineering Contradiction:

Improveuser safety and sensor protectionVSAvoidcomplexity of determining actuation direction and step count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The sensor surface is divided into multiple sensor surfaces arranged in groups, where each group contains sensor surfaces that are electrically conductively connected. This segmentation allows the system to determine actuation direction and step count by evaluating which specific sensor surfaces within a group are activated, thereby reducing the complexity of the overall evaluation process while maintaining safety and protection benefits.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If multiple sensor surfaces are arranged in groups with conductive connections, then cost-effectiveness is improved, but the ability to determine actuation direction without mechanical displacement becomes more difficult

Engineering Contradiction:

Improvecost-effectivenessVSAvoiddifficulty of determining actuation direction

Core Design Contradiction:

Ease of manufactureVSDifficulty of detecting and measuring

Solution Approach 1:

The evaluation circuit analyzes the output signals from sensor surfaces in groups to determine actuation direction and step count. By providing feedback information about which sensor surfaces are activated and their spatial relationships, the system can determine direction without mechanical displacement while maintaining cost-effectiveness through the grouped conductive connection structure.

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If sensor surfaces are covered by insulating cover plates, then protection against contamination is improved, but the ability to distinguish valid actuation from contamination decreases

Engineering Contradiction:

Improveprotection against contaminationVSAvoidability to distinguish valid actuation from contamination

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The insulating cover plate is provided with localized touch-sensitive areas that correspond to the sensor surfaces. This local quality differentiation allows the system to distinguish between valid actuations (which occur at specific touch-sensitive areas) and contamination (which may occur elsewhere on the cover plate), thereby maintaining both protection and reliability.

Inventive Principle:

Principle #3Local quality

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 cost-effective incremental encoding without mechanical displacement, improves operational reliability by distinguishing valid actuation from contamination, and reduces component count through time-division multiplexing and integrated signal processing.

Implementation Method 1

parts of capacitors having a capacitance that can be changed by touching the cover plate

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

the capacitive coupling between the electrode of the first group and the adjacent electrodes of the other two groups changes

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Implementation Method 3

The sensor surfaces are covered by an electrically insulating cover plate

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Implementation Method 4

each group is connected to an evaluation circuit in such a way that an output signal can be evaluated for each group

Methodology Applied

Scientific EffectElectrical signal detection: Conduction (electrical)

Data Source

PatentEP1953915B1Capacitative incremental encoder and household device with such an encoder

Publication Date: 2016.04.13 BSH HAUSGERATE GMBH

Figure 1
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Figure 3A~3B

AI summary

The invention relates to a capacitive incremental encoder with at least three groups (7i) of individual sensor surfaces (7ij), all sensor surfaces (7ij) of the same group (7i) being electrically conductively connected to one another, the sensor surfaces (7ij) covered by an electrically insulating cover plate (2) are covered and are parts of capacitors with a capacity that can be changed by touching the cover plate (2), with one sensor surface (7kj, 7mj) from each of the other groups (7i) between two sensor surfaces (7ij+1) of the same group (7i). 7k, 7m). Each group (71, 72, 73) is connected to a voltage source (25) so that each group (71, 72, 73) can be supplied with a voltage input signal, and each group (71, 72, 73) is connected to a Evaluation circuit (14) connected, so that for each group (71, 72, 73) a respective output signal (S) can be evaluated.