Capacitive Motion Sensor Bracket Layout to Block Water Noise
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Solution Overview
Problem
Conventional motion detection devices with capacitive sensor electrodes face challenges in distinguishing between human motion and noise, such as water entry, due to insufficient separation between sensor electrodes, leading to reduced detection accuracy.
Innovation Solution
The motion detection device incorporates a sensor bracket with a holding piece that elevates the sensor electrode at least 15 mm from the inner surface of the attached member, along with a U-shaped support block and drainage features to prevent water from reaching the sensor electrodes, thereby reducing noise detection from water ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensor electrodes are disposed close to the inner surface of the attached member, then the device complexity is reduced and ease of manufacture is improved, but water can easily reach the sensor electrodes causing noise detection and reduced measurement precision
Solution Approach 1:
The holding piece acts as an intermediary structure between the sensor electrode and the inner surface of the attached member. It extends from the inner surface to hold the sensor electrode at a separated position (15mm or more), preventing water that flows along the inner surface from directly reaching the sensor electrode while maintaining structural simplicity
Solution Approach 2:
The solution moves the sensor electrode separation problem from a two-dimensional plane (close to surface) into the third dimension (vertical separation). By extending the holding piece vertically from the inner surface to elevate the sensor electrode, the design creates spatial separation that prevents water contact while maintaining attachment simplicity
2Measurement precision
If the separation distance between sensor electrodes is increased to improve detection accuracy, then measurement precision is improved, but the device requires more space and may not fit within size constraints of the attached member
Solution Approach 1:
The holding piece creates a localized separation structure only where needed - at the sensor electrode attachment point. This allows the sensor electrode to be positioned 15mm or more from the inner surface for improved detection accuracy, while the rest of the attached member maintains its original compact dimensions and shape
3Ease of operation
If sensor electrodes are attached directly to the inner surface, then ease of operation and maintenance is improved, but water ingress detection accuracy is reduced due to noise from water contact
Solution Approach 1:
The holding piece serves as a simple intermediary that maintains sensor electrode attachment while preventing water contact. The sensor electrode is held by the holding piece rather than directly contacting the inner surface, keeping the system easy to operate and maintain while eliminating water-induced noise that reduces measurement precision
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 effectively suppresses noise detection from water entry, enhancing the accuracy of human motion detection while allowing for easy sensor electrode attachment and drainage of water, thus improving the overall performance of the motion detection system.
Implementation Method 1
a motion detection device equipped with a capacitive sensor electrode as a sensor that detects a motion of a person
Implementation Method 2
the holding piece holds the sensor electrode at a position at which an axis of the sensor electrode is separated from the inner surface by at least 15 mm or more
Data Source
AI summary
A motion detection device includes an attached member on a vehicle body side, a sensor electrode configured to detect capacitance, and a sensor bracket. The sensor bracket has a sensor holding portion holding the sensor electrode and is attached to an inner surface of the attached member. The sensor holding portion includes a holding piece that extends from a side away from an inner surface of the attached member to a side approaching the inner surface and holds the sensor electrode, and the holding piece holds the sensor electrode at a position at which an axis of the sensor electrode is separated from the inner surface of the attached member by at least 15 mm or more.