Capacitive Door Sensor with Anisotropic Connection Member
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Solution Overview
Problem
Capacitive door sensors in electronic devices, such as refrigerators and ovens, malfunction due to parasitic capacitance when adjacent to other conductive devices, leading to unstable operation and incorrect touch signal detection.
Innovation Solution
A capacitive door sensor design with a connection member having electrically non-conductive surfaces in the width direction, reducing the influence of parasitic capacitance, and including a conductive land and sensor substrate with support members made of insulating materials to enhance stability, allowing for accurate touch input detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitive door sensor is used to detect touch input, then touch detection function is enabled, but parasitic capacitance from adjacent conductive devices causes malfunction and unstable operation
Solution Approach 1:
An insulating member is introduced as an intermediary between the touch key and the conductive housing. This insulating member blocks the parasitic capacitance coupling path from adjacent conductive devices to the sensor circuit, thereby eliminating the harmful interference while preserving the touch detection function
Solution Approach 2:
The housing is designed with differentiated electrical properties in different regions: the main body remains conductive for structural integrity and EMI shielding, while specific local regions (where the insulating member is positioned) have insulating characteristics to block parasitic capacitance. This localized modification targets the harmful effect without compromising overall device functionality
2Object-affected harmful factors
If the connection member has electrically non-conductive surfaces in the width direction, then parasitic capacitance is reduced, but manufacturing complexity increases
Solution Approach 1:
The connection member is designed with differentiated electrical properties in different directions: electrically non-conductive surfaces in the width direction to block parasitic capacitance, and electrically conductive surfaces in the thickness direction to maintain electrical connection. This anisotropic design targets parasitic capacitance reduction without requiring complete redesign of the connection member
Solution Approach 2:
The connection member exhibits asymmetric electrical conductivity: insulating in the width direction (perpendicular to door opening/closing) and conducting in the thickness direction (parallel to door opening/closing). This asymmetric design selectively blocks parasitic capacitance while preserving necessary electrical connections
3Reliability
If support members made of insulating materials are used, then operational stability is enhanced, but device complexity increases
Solution Approach 1:
Insulating support members are positioned as intermediaries between the sensor substrate and the housing. These support members provide mechanical support while electrically isolating the sensor circuit from the conductive housing, preventing parasitic capacitance formation and enhancing operational stability
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 significantly reduces the risk of malfunction caused by parasitic capacitance, improving the operational stability and accuracy of touch signal detection for capacitive door sensors in electronic devices.
Implementation Method 1
When a user's hand touches the touch key, capacitance changes. The sensor detects whether there is a touch based on a change in capacitance.
Implementation Method 2
Capacitive door sensors in electronic devices, such as refrigerators and ovens, malfunction due to parasitic capacitance when adjacent to other conductive devices
Data Source
AI summary
An electronic device including a main body having an opening, a door configured to open and close at least a part of the opening of the main body, and a door sensor, provided relative to an open-side edge of the door, to detect a touch input by using a capacitive method. The door sensor includes a touch key configured to receive the touch input, a sensor substrate comprising a conductive land; a connection member including a sensing surface contacting the touch key, and a connection surface contacting the conductive land so that the touch key is electrically connected with the conductive land through the connection member. Surfaces of the connection member along a thickness direction including the sensing surface and the connection surface and surfaces of the connection member along a longitudinal direction are electrically conductive surfaces. Surfaces of the connection member along a width direction are electrically non-conductive surfaces.