Capacitance Sensor Rainwater Detection Threshold
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Solution Overview
Problem
Existing key-less entry systems using electrostatic capacitance type touch sensors face erroneous detection due to rainwater accumulation, leading to increased floating capacitance and incorrect user contact detection, which complicates sensor electrode and housing designs, reducing productivity.
Innovation Solution
A capacitance type detection device with a sensor unit that measures the time rate-of-change of floating capacitance to differentiate between the approach of the detection object and other objects, using a threshold table and judgment unit to accurately detect the detection object, while maintaining a simple configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact detection sensitivity of the sensor electrode at a portion near to the door panel is made lower than the contact detection sensitivity of the sensor electrode at a portion far from the door panel, then erroneous detection caused by rainwater accumulation is prevented, but the shape of the sensor electrode becomes complicated and/or the constitution of the housing of the door handle becomes complicated, which causes the productivity of the products to lower
Solution Approach 1:
The patent divides the sensor electrode into multiple regions with different detection thresholds. The first region (near door panel) uses a higher threshold to prevent false detection from rainwater, while the second region (far from door panel) uses a lower threshold for normal contact detection. This local differentiation of detection characteristics resolves the contradiction by applying different quality parameters to different parts of the same component.
Solution Approach 2:
The patent changes the detection parameter (threshold value) based on the spatial position of the sensor electrode. By setting different threshold values for different regions, the system adapts the detection sensitivity to local conditions, preventing rainwater-induced false detection while maintaining normal contact detection capability without complicating the physical structure.
2Reliability
If the contact detection sensitivity of the sensor electrode at a portion near to the door panel is made lower than the contact detection sensitivity of the sensor electrode at a portion far from the door panel, then erroneous detection caused by rainwater accumulation is prevented, but the constitution of the housing of the door handle becomes complicated, which causes the productivity of the products to lower
Solution Approach 1:
The patent introduces a dielectric member with different dielectric constants in different regions of the housing. The first dielectric member (near door panel) has a lower dielectric constant to reduce capacitance change from rainwater, while the second dielectric member (far from door panel) has a higher dielectric constant to enhance normal contact detection. This local differentiation resolves the contradiction without complicating the overall housing structure.
Solution Approach 2:
The patent uses composite dielectric members with different material properties in different regions of the housing. By combining materials with different dielectric constants in a structured arrangement, the system achieves region-specific detection characteristics while maintaining a unified housing structure, thus improving reliability without significantly increasing device complexity.
3Reliability
If a notch portion is formed at a portion of the sensor electrode near to the door panel, then the floating capacitance increase due to rainwater accumulation is reduced, but the shape of the sensor electrode becomes complicated, reducing product productivity
Solution Approach 1:
Instead of changing the physical shape of the sensor electrode (which would complicate manufacturing), the patent changes the electrical parameter (threshold value) for different regions. This parameter-based solution achieves the same functional effect of reducing rainwater-induced false detection while maintaining a simple, easy-to-manufacture electrode structure.
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 prevents erroneous detection of waterdrops or water currents, ensuring accurate detection of the detection object without complicating the sensor or housing design, thus maintaining high product productivity.
Implementation Method 1
a sensor electrode forming a capacitor with respect to a peripheral conductor; a measurement unit configured to measure the floating capacitance of the sensor electrode
Implementation Method 2
an antenna unit configured to carry out transmission and reception of a radio signal
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Disclosed are a device and a method for accurately detecting an approach of an object to be detected. Specifically, a measurement unit (210) measures the stray capacitances of first and second sensor electrodes (120, 133), and a determining unit (220) calculates average rates of change of the measured stray capacitances with respect to time during a period having a predetermined time length on the basis of the measured stray capacitances. Subsequently, the determining unit (220) determines whether or not an approach detection condition is satisfied, the condition including a predetermined relationship between the magnitude of a predetermined time rate-of-change with respect to time determined in accordance with a combination of the object to be detected and another object that should be discriminated from the object to be detected and the magnitude of the calculated average rates of change with respect to time. The determining unit (220) determines that the object to be detected has approached when the approach detection condition is satisfied.