Capacitive Touch Circuit Underwater Mode Detection
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Solution Overview
Problem
Conventional capacitive touchpads are unable to effectively determine touch positions when operated underwater due to water interference, which causes false readings similar to an entire hand pressing on the pad.
Innovation Solution
The method involves an operating mode distinguishing technique that differentiates between normal and underwater modes based on self and mutual capacitance values, switching to an underwater mode when the mutual capacitance rising range exceeds a threshold, and using a common electrode to detect capacitance values between sensing electrodes and the common electrode, along with a position correcting correspondence table to accurately determine touch points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional capacitive touchpad is used, then it can detect touch positions in normal conditions, but it cannot effectively determine touch positions when operated underwater due to water interference
Solution Approach 1:
The touch control circuit dynamically switches between normal mode and underwater mode based on detected capacitance characteristics. The system adapts its operating parameters in real-time: in normal mode it uses conventional self-capacitance or mutual-capacitance detection, while in underwater mode it switches to a specialized detection algorithm that accounts for water's high dielectric constant, thereby maintaining reliable touch position detection across both environments
Solution Approach 2:
The invention changes the detection parameters based on the operating environment. When underwater operation is detected (through characteristic capacitance changes caused by water's dielectric properties), the system modifies its capacitance detection thresholds, scanning patterns, or calculation algorithms to compensate for the water interference, thus restoring accurate touch position determination
2Loss of information
If water covers the top of the substrate, then it causes an effect similar to an entire hand pressing upon the capacitive touchpad, but the invention can distinguish underwater mode from normal touch
Solution Approach 1:
The system continuously monitors capacitance values across the touchpad surface and uses this feedback to distinguish between water coverage and actual touch input. By analyzing the spatial distribution and magnitude of capacitance changes, the system can identify the characteristic pattern of water interference (affecting the entire surface uniformly) versus localized finger touch, thereby preventing false readings while maintaining sensitivity to genuine user input
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
Enables accurate touch point detection and positioning in underwater environments, overcoming the limitations of conventional capacitive touchpads by distinguishing operating modes and correcting for substrate deformation caused by water.
Implementation Method 1
obtaining a self capacitance value and a mutual capacitance value in the capacitive touch apparatus; entering a first operating mode when a change in the self capacitance value does not exceed a first threshold and a rising range of the mutual capacitance value is greater than a second threshold
Data Source
AI summary
An operating mode distinguishing method, a touch point determining method and a touch control circuit are provided. It is determined whether an underwater mode is entered according to a self capacitance value and a mutual capacitance value. In the underwater mode, a touch point position is determined according to deformation of a substrate.