Capacitive Touch Frequency Selection for EMI-Resistant Response
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Solution Overview
Problem
Existing capacitive touch sensors for controlling devices, such as household appliances, face interference from electromagnetic signals, leading to unreliable determinations and a less spontaneous response, which can be uncomfortable for users.
Innovation Solution
The solution involves a sensor system with a signal generator providing a drive signal at a predetermined frequency, an evaluation device determining measurement noise at different frequencies, and a controller that adapts the frequency based on noise levels to optimize sensor signal determination, ensuring fast response and interference immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the frequency of the drive signal is changed according to a predetermined pattern to suppress interference, then interference immunity is improved, but response speed deteriorates
Solution Approach 1:
The patent applies dynamics by making the drive signal frequency adjustable and adaptive rather than fixed. The control device dynamically selects between a first frequency and a second frequency based on real-time assessment of electromagnetic interference conditions, allowing the system to optimize between interference immunity and response speed according to actual operating conditions.
Solution Approach 2:
The patent implements parameter changes by varying the drive signal frequency as a controllable parameter. The control device changes the frequency parameter of the drive signal based on detected interference levels, transitioning between different frequency states to maintain optimal performance in varying electromagnetic environments.
2Reliability
If a time average of capacitances is used to detect touch, then interference suppression is improved, but response spontaneity deteriorates
Solution Approach 1:
The patent applies dynamics by enabling the system to adaptively switch between different detection approaches based on interference conditions. Rather than always using time averaging, the system can dynamically select between frequency-based differentiation methods and traditional detection, maintaining both interference suppression and spontaneous response characteristics.
Solution Approach 2:
The patent implements parameter changes by adjusting the detection parameters (such as frequency differentiation thresholds and time constants) based on the electromagnetic environment. This allows the system to optimize the balance between interference suppression and response spontaneity by changing detection parameters rather than using a fixed averaging approach in all conditions.
3Speed
If a fixed frequency drive signal is used, then response speed is maintained, but reliability deteriorates due to electromagnetic interference
Solution Approach 1:
The patent applies dynamics by implementing a dynamic frequency selection mechanism that monitors electromagnetic interference conditions and adjusts the drive signal frequency accordingly. This dynamic adaptation maintains determination reliability by avoiding frequencies that are susceptible to interference while preserving fast response characteristics.
Solution Approach 2:
The patent implements parameter changes by varying the drive signal frequency parameter based on detected interference conditions. The control device changes the frequency parameter to values that are less susceptible to electromagnetic interference, thereby maintaining both fast response and high reliability in varying environmental conditions.
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 allows for a fast and reliable touch detection with improved interference immunity, maintaining a quick response while minimizing noise interference, ensuring accurate control of devices.
Implementation Method 1
The operating device comprises an electrode whose touch by a user is determined by detecting how the capacitance of the electrode changes
Implementation Method 2
a signal generator for providing a drive signal with a predetermined frequency for the sensor surface
Data Source
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AI summary
An operating device comprises a sensor area; a signal generator for providing a control signal with a predetermined frequency to the sensor area; an evaluation device configured to provide a sensor signal dependent on the capacitance of the sensor area; and a control unit. The control unit is configured to determine measurement noise at the evaluation device at various frequencies and to select the frequency of the control signal for determining the sensor signal as a function of the determined measurement noise.