Window Sensor With Accelerometer For Tamper Detection
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Solution Overview
Problem
Existing window sensing devices require precise alignment and multiple magnets, making them inefficient for detecting open window sashes and limiting the window's opening distance, as they fail to distinguish between partially open and fully closed positions.
Innovation Solution
A window sensing device comprising a housing with an accelerometer, magnetic sensor, and electronic controller that outputs a wireless signal indicating the window's state, eliminating the need for a second magnet by sensing movement and magnet presence, allowing for secure arming and alarm triggering without alignment issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two magnets are used to detect both closed and partially open window positions, then the sensing capability is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the movement detection function from the magnetic sensing system by adding an accelerometer. This allows the magnetic sensor to focus solely on detecting magnet presence/absence while the accelerometer independently detects window movement, eliminating the need for a second magnet while maintaining both detection capabilities
Solution Approach 2:
The accelerometer serves multiple functions: it detects window movement to distinguish between partially open and fully open states, and provides tamper detection capability. This multi-functionality replaces what would otherwise require additional magnetic sensors and magnets
2Measurement precision
If precise alignment between magnet and magnetic sensor is required, then detection accuracy is improved, but ease of installation deteriorates
Solution Approach 1:
The accelerometer enables the system to self-adapt to installation variations by detecting actual window movement patterns. Rather than requiring precise pre-alignment, the system uses movement detection to determine when the window is truly open versus merely misaligned, making the installation process more forgiving
Solution Approach 2:
The accelerometer acts as an intermediary that translates physical window movement into detection signals. This mediation allows the magnetic sensor to operate without precise alignment requirements, as the accelerometer compensates for positioning variations by detecting actual sash movement
3Reliability
If the window can only be opened a small amount to avoid triggering the alarm, then false alarms are reduced, but adaptability deteriorates
Solution Approach 1:
The system dynamically adjusts its detection behavior based on accelerometer data. When movement is detected, the system transitions from a static magnetic presence/absence detection to a dynamic movement-aware state, allowing the window to be opened further without triggering false alarms while maintaining security
4Measurement precision
If movement detection is added to distinguish open positions, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the movement detection function with the existing security sensing system by integrating an accelerometer into the window sensing device. This consolidation allows movement detection to be added without requiring a completely separate system, and the accelerometer also provides tamper detection as an added benefit
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
Enables reliable detection of window movement and tampering, providing accurate alarm states and reducing the complexity of installation by using a single magnet, allowing for greater window opening without triggering false alarms.
Implementation Method 1
a magnetic sensor configured to sense presence of a magnet
Implementation Method 2
an accelerometer configured to sense movement of a window sash in a given direction
Data Source
AI summary
A window sensing device with movement detection enables use of a window sensing arrangement to provide an indication even when a window sash that is open is moved, while an alarm system is armed. The window sensing device includes an accelerometer configured to sense movement of a window sash in a given direction. A magnetic sensor is configured to sense presence of a magnet when the window sash is in a closed position. An electronic controller outputs a normal state wireless signal when the magnetic sensor senses the magnet and outputs an alarm state wireless signal when the magnetic sensor does not sense the presence of the magnet. When the electronic controller is outputting an alarm state wireless signal and the accelerometer senses movement of a window sash, the electronic controller outputs an indication of movement of a window sash in a given direction.