Capacitive Appliance Touch Control With Adaptive Noise Frequency Selection
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Solution Overview
Problem
Existing capacitive touch sensor operating devices for appliances, such as cookers, face interference issues from electromagnetic signals, leading to unreliable touch detection and a less spontaneous response behavior, which can be unpleasant for users.
Innovation Solution
The operating device employs a controller to determine measuring noise at different frequencies, selectively changing the frequency of the control signal to minimize interference, allowing for quick response and effective touch detection by using a moving average method and signal-to-noise ratio assessment to switch between primary and secondary frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the frequency of the control signal is changed in accordance with a predetermined pattern, then interference suppression is improved, but the response behavior becomes less spontaneous
Solution Approach 1:
The patent applies dynamics by making the frequency selection adaptive rather than static. The controller dynamically adjusts the control signal frequency based on real-time noise measurements, switching between a first frequency and a second frequency depending on which exhibits lower noise levels. This dynamic adaptation resolves the contradiction by allowing the system to maintain fast response when conditions permit while suppressing interference when necessary.
Solution Approach 2:
The patent implements feedback through continuous noise level monitoring and measurement. The controller measures noise at both frequencies, compares the results, and uses this feedback information to determine which frequency to use for control signals. This closed-loop feedback mechanism enables the system to automatically optimize its performance by selecting the cleaner frequency, thereby achieving both fast response and interference suppression.
2Reliability
If a temporal average value of determined capacitances is used to detect a touch, then interference suppression is improved, but the response behavior becomes less spontaneous
Solution Approach 1:
The patent applies parameter changes by switching the frequency parameter of the control signal based on noise conditions rather than using temporal averaging. By changing the frequency parameter dynamically, the system achieves interference suppression without the time delay inherent in averaging methods. This allows immediate touch detection while maintaining robustness against electromagnetic interference.
3Measurement precision
If the frequency of the control signal is changed to minimize noise, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the frequency domain into distinct segments (first frequency and second frequency). Rather than continuously varying the frequency or implementing complex adaptive algorithms, the system segments the frequency space and selects between discrete options based on noise measurements. This segmentation simplifies the control logic while maintaining measurement precision.
Solution Approach 2:
The patent employs a simple, lightweight frequency selection mechanism that does not require complex hardware or algorithms. By using basic noise measurement and comparison logic to switch between two predefined frequencies, the system achieves high measurement precision with minimal added complexity. The solution is economically efficient and easy to implement.
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 approach combines quick response behavior with robust interference resistance, ensuring reliable touch detection and minimizing user dissatisfaction due to interference, by dynamically selecting the most advantageous frequency for signal determination.
Implementation Method 1
The operating device has an electrode, the touch of which by a user is determined by detecting how the capacitance of the electrode changes
Implementation Method 2
a high- or low-frequency electromagnetic signal can be coupled in a cable-bound or wireless manner
Data Source
AI summary
An operating device contains a sensor surface, a signal generator for providing a control signal with a predetermined frequency for the sensor surface, an evaluation device which is configured to provide a sensor signal which is dependent on the capacitance of the sensor surface, and a control facility. In this process, the control facility is configured to determine measuring noise on the evaluation device at different frequencies and to select the frequency of the control signal in order to determine the sensor signal as a function of the determined measuring noise.