Capacitive Touch Sensor Noise Synchronization
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Solution Overview
Problem
Touch sensors, particularly those using capacitive sensing, face challenges in reducing noise-induced interference from sources like LCD screens, which can lead to false object detection or failure to detect objects due to noise signals, especially in environments where physical shielding is undesirable due to size and cost considerations.
Innovation Solution
A sensor system that includes a capacitance measurement circuit and a controller circuit capable of detecting periodic noise signals and synchronizing measurement cycles with the noise signal's stable phases, thereby reducing noise interference and enhancing object detection accuracy without the need for additional shielding components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If physical shielding components are added to reduce noise interference, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces physical/mechanical shielding components with an electronic/software-based solution. The controller circuit detects periodic noise signals and synchronizes measurement cycles to perform measurements during stable phases of the noise signal, thereby eliminating the need for additional shielding hardware while maintaining measurement precision.
Solution Approach 2:
The patent changes the timing parameter of measurements by synchronizing them with the noise signal's periodic pattern. By adjusting when measurements are taken (during stable phases rather than during high-noise phases), the system achieves accurate detection without adding physical shielding components.
2Productivity
If measurement cycles are performed continuously, then productivity is improved, but measurement precision deteriorates due to noise interference
Solution Approach 1:
The patent implements periodic measurement cycles that are synchronized with the periodic noise signal. Instead of continuous measurements, the system performs measurements at specific intervals during the stable phases of the noise pattern, maintaining productivity while avoiding noise-induced errors.
Solution Approach 2:
The controller circuit performs preliminary detection of the noise signal's periodic pattern and identifies stable phases before executing measurement cycles. This preliminary action allows the system to schedule measurements optimally, ensuring both high productivity and precision by avoiding noisy periods.
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
The solution effectively reduces noise-induced errors in object detection, allowing for reliable operation of touch sensors in noisy environments without increasing device size or cost, and enables self-contained touch sensors that can be integrated with LCD screens without additional electrical coupling.
Implementation Method 1
sensor which is arranged to determine the presence of an object from a change in a capacitance of a sensing element
Implementation Method 2
When a pointing object for example a user's finger approaches the sensing electrode (plate), the pointing object appears to be a virtual ground. This serves to increase the measured capacitance of the sensing electrode to ground.
Data Source
AI summary
A sensor is arranged to determine the presence of an object from a change in a capacitance of a sensing element. The sensor includes a capacitance measurement circuit operable to perform measurement cycles to measure a capacitance of the sensing element, and a controller circuit. The control circuit is operable to detect a periodic noise signal induced on the sensing element, to determine a first part, of a repeating pattern of the periodic noise signal, which causes a change in an amount of charge present on the sensing element, which affects the measurement of the capacitance of the sensing element by the capacitance measurement circuit, to determine a second part of the repeating pattern of the periodic noise signal, which does not cause a change in the amount of charge present on the sensing element, and to control the measurement cycles of the capacitance measurement circuit to perform the measurement cycles during the second part of the periodic noise signal and not to perform the measurement cycles during the first part of the periodic noise signal.