Proximity control device and domestic electrical appliance equipped therewith
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Solution Overview
Problem
Domestic electrical appliances with metallic housings interfere with capacitive proximity sensors, causing false object detection due to capacitance changes from vibrations and metal presence, making reliable user control gestures difficult to detect.
Innovation Solution
A proximity control device with a pair of planar sensor electrodes and an electronic assembly that generates and correlates sensor signals to differentiate between user control gestures and interfering vibrations, using one electrode as a 'hand' sensor and the other as an 'appliance' sensor to distinguish between intentional and unintentional signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive proximity sensor is used in a domestic electrical appliance with metallic housing, then the sensor can detect user proximity gestures, but the metallic housing causes false detections due to capacitance changes from vibrations and metal presence
Solution Approach 1:
The sensor system is divided into two separate sensor electrodes instead of using a single sensor. Each electrode independently measures capacitance changes, allowing the system to distinguish between vibrations (affecting both electrodes similarly) and genuine user gestures (affecting one electrode more significantly). This segmentation enables differentiation between true signals and interference from the metallic housing.
Solution Approach 2:
The system monitors changes in capacitance parameters of two separate electrodes and compares their differential behavior. By analyzing how capacitance changes differ between the two electrodes rather than relying on absolute capacitance values, the system can identify genuine user gestures against the background of housing vibrations and metallic interference.
2Device complexity
If a single capacitive sensor electrode is used, then the device structure remains simple, but the system cannot distinguish between user gestures and vibrations of the housing walls
Solution Approach 1:
Instead of using a single sensor electrode, the system employs two separate sensor electrodes arranged on the housing surface. This segmentation allows the system to compare capacitance changes between the two electrodes, enabling distinction between housing vibrations (which affect both electrodes similarly) and genuine user proximity gestures (which create asymmetric capacitance changes).
Solution Approach 2:
The system combines the signals from two sensor electrodes through differential evaluation. By merging the measurement data from both electrodes and analyzing their relative differences, the system achieves enhanced gesture detection accuracy while filtering out common-mode vibrations affecting the housing structure.
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 reliable detection of user control gestures by distinguishing between signal patterns caused by user interaction and appliance vibrations, ensuring accurate operation of domestic appliances.
Implementation Method 1
Capacitive proximity sensors work by the principle that, by moving an object into the electric field of an (open) capacitor, the capacitance of the capacitor changes
Implementation Method 2
by moving an object into the electric field of an (open) capacitor, the capacitance of the capacitor changes
Implementation Method 3
each of the pair of sensor electrodes forms a capacitor electrode of a plate-type capacitor. For each of the two sensor electrodes, a sensor signal is generated by the electronic assembly, for example by means of a suitable oscillator circuit, which sensor signal represents capacitance changes of the plate-type capacitor in question
Data Source
AI summary
A capacitive proximity control device (28) for a domestic washing machine (10) or other domestic electrical appliance is proposed. In some embodiments, the proximity control device comprises two planar sensor electrodes (34, 36) arranged on a door (20) of the washing machine at a spatial distance from one another. An electronic assembly is connected to the two sensor electrodes, which electronic assembly is adapted to generate, in association with each of the two sensor electrodes, an electrical sensor signal which is representative of a change in a capacitance associated with the sensor electrode in question. By mutual correlation of the two sensor signals, the electronic assembly is able to determine a proximity operation of the control device. A shielding electrode can be arranged in the spatial region between the two sensor electrodes.