Capacitive Sensor Oscillation Control for Design Flexibility
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Solution Overview
Problem
Multi-channel capacitive proximity or touch sensors face limitations due to the need for uniform static or parasitic capacitance among sensing capacitors, restricting flexibility in design and accuracy, as well as the ability to improve spatial resolution, due to the use of a single processor for detecting changes in oscillation frequencies.
Innovation Solution
The solution involves a configurable capacitive sensor system with a controller that adjusts the oscillation period and gating duration for each sensing region, allowing for different capacitance values and enabling accurate detection of touch or proximity by determining the number of oscillation periods over a controlled gating duration, and a calibration method to optimize these parameters for each sensing region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single processor is used to detect changes in capacitance of multiple sensing capacitors, then costs are lowered, but the sensing capacitors must have the same or similar static capacitance which limits design flexibility and spatial resolution
Solution Approach 1:
The system dynamically adjusts the oscillation period for each sensing capacitor based on its individual capacitance characteristics. The controller modifies the oscillation period adaptively, allowing each sensing capacitor to operate optimally regardless of its static capacitance value, thereby enabling design flexibility while using a single processor.
Solution Approach 2:
The system changes the oscillation period parameter for each sensing capacitor according to its capacitance value. By adjusting this parameter, the system compensates for variations in static capacitance among different sensing capacitors, enabling accurate touch detection across multiple channels with different capacitance values.
2Manufacturing precision
If sensing capacitors have different capacitance values, then design flexibility and spatial resolution can be improved, but the oscillation frequencies will vary widely making accurate detection difficult with a single processor
Solution Approach 1:
The system dynamically adjusts the oscillation period for each sensing capacitor based on its individual capacitance characteristics. The controller modifies the oscillation period adaptively, allowing each sensing capacitor to operate optimally regardless of its static capacitance value, thereby enabling design flexibility while using a single processor.
Solution Approach 2:
The system performs preliminary calibration to determine the capacitance value of each sensing capacitor before actual touch detection. This preliminary action allows the system to pre-adjust the oscillation period for each capacitor, ensuring accurate detection during normal operation without being affected by capacitance variations.
3Device complexity
If the oscillation period is fixed for all sensing capacitors, then the system is simpler to control, but capacitors with different capacitance values cannot be used effectively
Solution Approach 1:
The system dynamically adjusts the oscillation period for each sensing capacitor based on its individual capacitance characteristics. The controller modifies the oscillation period adaptively, allowing each sensing capacitor to operate optimally regardless of its static capacitance value, thereby enabling design flexibility while using a single processor.
Solution Approach 2:
The controller is designed to universally handle multiple sensing capacitors with different capacitance values. By implementing adaptive oscillation period adjustment, the single controller can effectively manage diverse sensing capacitors, achieving multi-functionality and broad capacitor compatibility without increasing system complexity significantly.
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 flexible design and improved accuracy in multi-channel sensors by maintaining a consistent ratio of oscillation periods, enabling accurate detection of touch or proximity across sensing regions with varying capacitance, while also ensuring efficient scanning and electromagnetic compatibility.
Implementation Method 1
A proximity or touch sensor may function by detecting a change in capacitance of a sensing capacitor of the sensor due to contact or proximity of the object
Implementation Method 2
The change in capacitance may in turn be detected by detecting a change in frequency of an oscillating signal generated by an oscillator circuit comprising that sensing capacitor
Data Source
AI summary
A sensor for sensing proximity or touch of an object includes a sensing region, an oscillating signal generator for generating an oscillating signal having an oscillation period, a gating signal generator for generating a gating signal having a gating duration, a controller for controlling the oscillation period or the gating duration and a processor for determining a number N of oscillation periods over the gating duration. The number N is indicative of the object's contact with, or proximity to, the sensing region. The sensor is calibrated by determining an optimal value for the oscillation period or gating duration such that an optimal number N over the gating duration is expected.