Compact Reed-Switch Fall Sensor for Omnidirectional Detection
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Solution Overview
Problem
Conventional fall detection sensors using reed switches are limited in size due to vertical orientation and have dead regions where inclinations orthogonal to the reed switch cannot be detected, leading to unstable on/off states and sensitivity to external magnetic fields and vibrations.
Innovation Solution
A compact fall detection sensor design featuring a non-magnetic case with a recessed curved surface, a magnet with magnetic poles aligned parallel to the reed switch, and magnetic fluid for smooth magnet movement, ensuring stable on/off states and detection in all directions by positioning magnetic poles to magnetize reeds differently based on inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reed switch is arranged vertically in the upright state, then the sensor can detect inclination, but the size of the sensor becomes large in the vertical direction
Solution Approach 1:
The reed switch is inverted from vertical arrangement to horizontal arrangement in the upright state. This inversion allows the sensor to maintain inclination detection capability while reducing the vertical size, as the reed switch now extends horizontally rather than vertically.
Solution Approach 2:
The reed switch is reoriented from a vertical dimension to a horizontal dimension. By changing the orientation dimension, the sensor achieves the same detection function while occupying less vertical space, effectively trading vertical extent for horizontal placement.
2Device complexity
If the permanent magnet is placed at the center of the bottom face, then the sensor structure is simple, but the on state is not maintained stably when the magnet deviates with inclination
Solution Approach 1:
An auxiliary magnet is introduced as an intermediary element to work together with the permanent magnet. The auxiliary magnet, positioned near the reed switch, ensures stable magnetization of the reed switch contacts during inclination, maintaining reliable on/off states even when the permanent magnet deviates from the center position.
3Volume of moving object
If the reed switch is placed horizontally in the upright state, then the sensor becomes compact, but dead regions exist where inclination orthogonal to the reed switch cannot be detected
Solution Approach 1:
The combination of the permanent magnet and auxiliary magnet creates a multi-functional magnetic field system that provides both compact housing and omnidirectional detection capability. The auxiliary magnet extends the detection sensitivity to include directions orthogonal to the reed switch, making the sensor universally responsive to inclination from any direction while maintaining a compact form factor.
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 sensor effectively detects inclinations and falls in all directions, maintaining stable on/off states and resisting external effects like magnetic fields and vibrations, while maintaining a compact size.
Implementation Method 1
magnetic fluid which is sealed in the hollow portion and is magnetically attached to at least both ends of the magnetic poles of the magnet
Implementation Method 2
each magnetic pole of the magnet respectively magnetizes a corresponding reed of the reed switch positioned immediately below the magnet, thus allowing one of the reeds of the reed switch to be magnetized to N pole, whereas the other reed to be magnetized to S pole, to attract each other
Implementation Method 3
allowing only one of the magnetic poles of the magnet to be positioned around the central axis, and thus the magnetic poles magnetize each reed of the reed switch to the same pole, turning off the reed switch
Implementation Method 4
when the object inclines from the upright state, the magnet slides along the curved surface of the case, deviating from the central axis of the case
Data Source
AI summary
A compact fall detection sensor includes a case. A magnet is housed in the case. A reed switch with a pair of reeds are integrally positioned around the central axis of the case at the bottom of the case. In an upright state, the magnet is gravitationally positioned in the longitudinal direction of the reed switch around the central axis of the curved surface of the case, each magnetic pole magnetizing the corresponding reed of the reed switch, allowing one of the reeds to be magnetized to N pole and the other reed to S pole to turn on the switch. When inclined from the upright state, the magnet slides along the curved surface of the case and deviates from the central axis, to position only one of the magnetic poles of the magnet around the central axis to turn off the reed switch.