Multi-Electrode Electrostatic Sensing for Wet Finger Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electrostatic detection sensors face challenges in detecting fingers accurately when exposed to water due to water interference and are prone to reduced detection precision from vibrations or thermal shocks, which alter the distance between electrodes.
Innovation Solution
The electrostatic detection sensor design includes a first electrode, a second electrode surrounding the first, and a third electrode with a predetermined angle, along with a controller that applies specific drive voltages to determine object approaches by computing temporal changes in capacitance intensities, and is supported by a substrate and fixing member to maintain electrode distances and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the electrostatic detection sensor is exposed to water during rainfall or vehicle wash, then the sensor can detect objects in outdoor environments, but water may flow on the sensor body and cause detection failure
Solution Approach 1:
The sensor body is divided into multiple electrodes (first electrode, second electrode, third electrode) with distinct functions. The first and second electrodes detect object approach, while the third electrode specifically detects water presence. This segmentation allows the sensor to differentiate between valid detection targets and water interference, maintaining reliability in outdoor environments.
Solution Approach 2:
The third electrode acts as an intermediary that specifically detects water presence and provides this information to the control unit. The control unit then uses this water detection information to adjust or inhibit the detection results from the first and second electrodes, effectively filtering out water-related false signals while preserving genuine object detection capability.
2Adaptability or versatility
If the touch electrode and touch electrode for difference correction are disposed to be mutually orthogonal, then both electrodes can be separately provided for comprehensive detection, but vibration or thermal shock changes the distance between electrodes and deteriorates detection precision
Solution Approach 1:
The first electrode and second electrode are positioned adjacent to each other in the same plane rather than being orthogonally separated. This merging of spatial arrangement allows both electrodes to function together for comprehensive detection while maintaining constant relative positioning, thereby preventing detection precision deterioration from vibration or thermal shock.
Solution Approach 2:
The sensor electrodes are formed on flexible printed substrates that can accommodate thermal expansion and vibration without changing the relative distances between electrodes. This flexible substrate approach maintains detection precision while allowing the sensor to cover comprehensive detection areas.
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 configuration enables high-precision detection of objects, such as fingers, even in wet conditions and maintains detection accuracy despite vibrations or thermal shocks, improving overall sensor reliability.
Implementation Method 1
a first intensity corresponding to capacitance between the first electrode and the second electrode by applying a first drive voltage to the first electrode and the second electrode
Implementation Method 2
a second intensity corresponding to capacitance of the first electrode by applying a second drive voltage to the first electrode while connecting the second electrode and the third electrode to a ground potential
Implementation Method 3
a third intensity corresponding to capacitance of the third electrode by applying a third drive voltage to the third electrode while connecting the first electrode to a ground potential
Data Source
AI summary
The electrostatic detection sensor has a first electrode, a second electrode, and a third electrode. A controller connects the first electrode and the second electrode, and applies a first drive voltage thereto to obtain a first intensity. The controller applies a second drive voltage to the first electrode while keeping the second electrode and the third electrode at a ground potential to obtain a second intensity. The controller applies a third drive voltage to the third electrode while grounding the first electrode to the ground potential and keeping the second electrode open to obtain a third intensity. Then, the controller determines whether an object is approaching based on first, second, and third computed values which are computed temporal changes in the first, second, and third intensities, respectively.