Capacitive Touch Sensor Timing Against Cyclic Noise
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Solution Overview
Problem
Touch sensors often inaccurately determine touch events due to cyclic noise, leading to false positives or false negatives in periodic sensor readings.
Innovation Solution
A circuit incorporating a random number generator and timer to randomly space trigger events for touch sensor determination, using a hardware-based random number generator to vary the timing of timer signals and improve the accuracy of touch event detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If periodic sensor touch determinations are made, then the sensor can continuously monitor for touch events, but cyclic noise repeatedly occurs causing false touch determinations
Solution Approach 1:
The patent applies dynamics by transitioning from fixed periodic sampling to dynamic random sampling. The sampling intervals are made variable through random number generation, allowing the system to adapt timing dynamically and avoid predictable patterns that coincide with cyclic noise, thereby improving reliability while maintaining productivity
Solution Approach 2:
The patent changes the temporal parameter of sampling by using random intervals instead of fixed periodic intervals. This parameter change disrupts the correlation between sampling timing and cyclic noise patterns, reducing false determinations while maintaining continuous monitoring capability
2Reliability
If random timing is introduced to avoid noise, then touch detection accuracy improves, but the complexity of the sensor circuit increases
Solution Approach 1:
The patent introduces a random number generator as an intermediary component between the timer and sensor circuit. This intermediary generates random timing values that mediate between the fixed clock signal and the variable sampling requirements, achieving noise avoidance while maintaining circuit modularity and manageable complexity
Solution Approach 2:
The patent replaces the mechanical/regular periodic timing mechanism with a digital random number generation system. This substitution uses digital logic and algorithms to create irregular timing patterns, achieving the desired randomness without complex analog circuitry while maintaining digital circuit simplicity
Data Source
AI summary
A circuit includes a timer to count edges of a clock from an initial count value to a terminal count value and to output a timer signal responsive to the terminal count value being reached. A random number generator circuit generates a plurality of random number values. Each generated random number value is sequentially loaded into the timer as one of the initial count value or the terminal count value. A capacitive sensor circuit determines, responsive to receipt of a plurality of timer signals from the timer, a touch event of a capacitive touch sensor.