Capacitive Touch Switches with Environmental Compensation
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Solution Overview
Problem
Capacitive user-interface switches face challenges in accurately sensing capacitance changes, particularly in varying environmental conditions such as temperature and humidity, and in providing responsive switching functions for diverse electronic devices like point of sale devices, mobile telephones, and televisions.
Innovation Solution
The implementation of capacitance sensors with plated-through holes or vias adjacent to the edges of printed circuit boards, coupled with capacitance change responsive switching circuitry, including environmental compensation, to sense changes in capacitance and provide switching functions responsive to object engagement, such as human appendages, with integrated circuit solutions like AD7142 or CapSense, which include integrators and comparators for precise detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If capacitance sensors are placed at the edges of printed circuit boards to enable capacitive touch sensing, then the device can detect capacitance changes from user interaction, but the sensing accuracy deteriorates due to environmental factors such as temperature and humidity variations
Solution Approach 1:
The patent implements environmental compensation functionality that continuously monitors environmental conditions (temperature, humidity) and adjusts the capacitance sensing parameters accordingly. The switching circuitry receives feedback about environmental changes and compensates for their effect on capacitance measurements, maintaining accurate detection despite varying environmental conditions.
Solution Approach 2:
The patent changes the operating parameters of the capacitance sensor based on environmental conditions. The switching circuitry adjusts sensing thresholds, integration times, and reference capacitance values dynamically to compensate for temperature and humidity effects, thereby maintaining measurement precision across different environments.
2Measurement precision
If multiple plated-through holes are used as capacitance sensors to improve detection capability, then the sensing precision is improved, but the device complexity increases due to additional circuitry and voltage management
Solution Approach 1:
The patent combines multiple plated-through holes into a single capacitance sensor assembly that functions as one integrated sensing element. The switching circuitry manages multiple sensors through unified control logic and shared signal processing paths, reducing overall system complexity while maintaining the enhanced detection capability provided by multiple sensing points.
Solution Approach 2:
The switching circuitry is designed to handle multiple capacitance sensors with different voltage requirements through a single multi-functional control unit. The same circuitry can selectively activate and manage sensors at different voltages, eliminating the need for separate dedicated circuitry for each sensor and reducing overall device complexity.
3Reliability
If environmental compensation functionality is added to compensate for temperature and humidity changes, then the reliability is improved, but the device complexity increases due to additional compensation circuitry
Solution Approach 1:
The environmental compensation functionality is merged into the existing switching circuitry rather than being implemented as a separate subsystem. The same circuit components perform both switching control and environmental compensation functions, reducing overall device complexity while maintaining improved reliability under varying temperature and humidity 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 solution enhances the responsiveness and reliability of capacitive switches by accurately detecting capacitance changes and compensating for environmental factors, enabling effective switching functions in various devices, including precise location and speed sensing, and adaptable to different electronic applications.
Implementation Method 1
at least one capacitance sensor located at the at least one edge of the printed circuit board and being adapted to sense a change in capacitance at the at least one corresponding edge region resulting from engagement therewith by an object having predetermined capacitance characteristics
Data Source
AI summary
An electronic device including a housing having an outer surface, at least one printed circuit board located within the housing and having at least one edge located in propinquity to at least one corresponding edge region of the outer surface, at least one capacitance sensor located at the at least one edge of the printed circuit board and being adapted to sense a change in capacitance at the at least one corresponding edge region resulting from engagement therewith by an object having predetermined capacitance characteristics and capacitance change responsive switching circuitry located within the housing and coupled to the at least one capacitance sensor for providing a desired switching function responsive to the engagement.