Capacitive Sensor Array Group Scanning for Sensitivity
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Solution Overview
Problem
Capacitive sense user interfaces face reduced sensitivity due to shrinking sensor size, which affects user experience, and thicker dielectric materials used in durable consumer products further impair sensitivity.
Innovation Solution
The implementation of a capacitive sense user interface that groups capacitive sensors into arrays, allowing for quick discrete scans to approximate interaction location and more precise group scans to increase sensitivity, using a capacitance sensor circuit with driver circuitry and a relaxation oscillator to measure capacitance changes, and configuring I/O interfaces to couple sensors individually or in groups for optimal scanning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of capacitive sensors is reduced to shrink the user interface, then the device size is reduced, but the sensitivity of the sensors deteriorates
Solution Approach 1:
The patent segments the sensor array into multiple groups that can be scanned sequentially. By dividing the sensing area into discrete groups and scanning them in sequence, the system maintains high sensitivity for each individual sensor element while achieving comprehensive coverage of the entire interface area, thus resolving the contradiction between small device size and sensor sensitivity.
Solution Approach 2:
The patent implements periodic scanning of sensor groups where each group is scanned for a predetermined time period, then the next group is scanned. This periodic action allows each small sensor to be monitored with sufficient sampling time to maintain sensitivity, while the overall interface remains compact due to the sequential scanning approach.
2Measurement precision
If the sampling time of capacitive sensors is increased to compensate for decreased sensitivity, then the sensitivity is improved, but the response time of the user interface deteriorates
Solution Approach 1:
By segmenting the sensor array into multiple groups and scanning each group sequentially, the system can allocate adequate sampling time to each group (improving sensitivity) while maintaining fast overall response through efficient sequential scanning. This segmentation allows the interface to respond quickly to user interactions without sacrificing the sampling time needed for sensitive detection.
Solution Approach 2:
The patent dynamically adjusts the scanning process by identifying which sensor group contains the user interaction and concentrating scanning resources on that group. This dynamic approach ensures that sufficient sampling time is devoted to the relevant sensors for accurate detection, while minimizing the total scanning time to maintain fast response to user input.
3Reliability
If thicker dielectric materials are used to protect capacitive sensors in harsh environments, then the durability is improved, but the sensitivity of the capacitive sense interface deteriorates
Solution Approach 1:
The patent segments the sensing interface into multiple sensor groups that can be scanned sequentially. This segmentation compensates for the reduced sensitivity caused by thicker dielectric materials by allowing longer sampling times for each group, thereby maintaining detection accuracy while using protective thicker dielectric layers for durability in harsh environments.
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 enhances the signal-to-noise ratio and sensitivity of capacitive sense interfaces, enabling effective operation in smaller devices and harsh environments while maintaining user experience.
Implementation Method 1
capacitance sensor circuit 305 measures a value indicative of a combined capacitance or a combined capacitance change
Implementation Method 2
capacitance sensor circuit with driver circuitry and a relaxation oscillator to measure capacitance changes
Data Source
AI summary
A technique for operating a capacitive sensor array is described. The technique includes measuring a first capacitance of a first set of electrodes at a first time, measuring a second capacitance of a second set of electrodes at a second time, and calculating a position of a conductive object based on a relative magnitude of the first capacitance and the second capacitance. The first set and the second set includes at least one electrode in common and at least one electrode that is not in common.