Multi-Controller Capacitive Sensing With Synchronized Shielding
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Solution Overview
Problem
Large capacitive sensing devices face challenges in control due to the finite number of connections a device controller has to signal lines, leading to difficulties in maintaining sensitivity and reducing noise from cross-coupling effects.
Innovation Solution
Implementing multiple device controllers connected to different portions of the capacitive sensors, with each controller including switching devices to control charging and discharging of drive and sense lines, and a common node or shield, synchronized to prevent overlapping charging and discharging events, and using shared reference capacitive sensors for capacitance comparison.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single device controller is used to control a large capacitive sensing device, then the device complexity is reduced, but the measurement precision and sensitivity deteriorate due to the finite number of connections available to signal lines
Solution Approach 1:
The capacitive sensing device is divided into multiple zones, with each zone controlled by a separate device controller. Each controller manages a specific portion of the sensing device, allowing for more connections and signal lines per controller, thereby maintaining high measurement precision and sensitivity even in large-scale devices.
2Measurement precision
If multiple device controllers are used to control different portions of capacitive sensors, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
Multiple device controllers are designed with identical or similar functional capabilities, each capable of controlling a zone of the capacitive sensing device independently. This multi-functionality allows the system to maintain high measurement precision across the entire device while managing complexity through standardized controller designs that can be replicated and coordinated.
3Measurement precision
If drive and sense lines are densely connected to maintain sensitivity in large devices, then the measurement precision is improved, but the object-generated harmful factors increase due to cross-coupling noise
Solution Approach 1:
The sensing device is segmented into multiple zones, each with its own drive and sense lines managed by a dedicated controller. This segmentation reduces the total number of lines interconnected within each zone, thereby reducing cross-coupling noise while maintaining sufficient connection density for high measurement precision in each local region.
Solution Approach 2:
Device controllers act as intermediaries between the drive lines, sense lines, and the processing system. Each controller manages the signaling within its zone, isolating the drive and sense lines from direct interaction with lines in other zones. This intermediary function reduces cross-coupling noise while maintaining the necessary signal integrity for precise measurement.
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 allows for scalable capacitive sensing systems, maintaining sensitivity and reducing noise, enabling effective force detection and touch interaction across larger surfaces while minimizing undesirable effects like cross-coupling noise.
Implementation Method 1
a capacitive sensing device capable of detecting changes in capacitance in response to an applied force
Implementation Method 2
detecting changes in capacitance in response to an applied force
Data Source
AI summary
A capacitive sensing device can include multiple capacitive sensors. A first device controller is operatively connected to a portion of the capacitive sensors, while a second device controller is operatively connected to another portion of capacitive sensors. A common node or shield can be connected between the first device controller and the second device controller. Charging and discharging events of selected drive lines in the capacitive sensing device and/or of the common node or shield can be synchronized to reduce undesirable effects such as noise and/or to prevent the charging events and the discharging events from overlapping with each other. One or more reference capacitive sensors can be shared by the multiple device controllers.