Smoke Detector Multi-Wavelength Particle Discrimination
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Solution Overview
Problem
Photo-electric smoke detectors fail to differentiate between large-size non-smoke particles and small-size non-smoke particles generated by cooking activities, leading to false alarms and non-compliance with UL 217-8 and 268-7 standards.
Innovation Solution
A photo-electric smoke detector with multiple light emitters and receivers, utilizing different wavelengths and angles of light emission to discriminate between particle sizes based on Rayleigh scattering principles, and a controller to process signals and determine whether to trigger an alarm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single light emitter and receiver are used in a photo-electric smoke detector, then the device structure is simple, but the device cannot discriminate between large-size non-smoke particles and small-size non-smoke particles generated by cooking activities
Solution Approach 1:
The patent divides the single light detection function into multiple light emitters and receivers, each configured at different angles. Specifically, it uses multiple light emitters (first, second, third light emitters) and multiple light receivers (first, second light receivers) arranged at different angles within the detection chamber, enabling the system to discriminate particle sizes by analyzing light scattering patterns from different directions
Solution Approach 2:
The patent introduces angular dimension to the light detection system by configuring light emitters and receivers at different angles (e.g., 30 degrees, 60 degrees, 90 degrees) relative to each other. This angular differentiation creates multiple detection dimensions, allowing the system to distinguish between particles of different sizes based on their scattering characteristics at various angles
2Reliability
If photo-electric smoke detector triggers alarm based on light reflection from particles, then fire detection sensitivity is high, but false alarms occur during cooking activities like broiling hamburgers
Solution Approach 1:
The patent implements feedback mechanisms where the controller receives signals from multiple light receivers, processes the light scattering data from different angles, and uses this feedback information to determine whether to trigger an alarm. The system continuously monitors light reflection patterns and adjusts its alarm decision based on the analyzed particle characteristics, preventing false alarms during cooking activities
Solution Approach 2:
The patent changes the detection parameters by using multiple light wavelengths and different detection angles. By analyzing light scattering at multiple angles (e.g., 30°, 60°, 90°) and comparing the results, the system can distinguish between fire particles and cooking-related particles, improving reliability without sacrificing detection 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
Effectively prevents false alarms during cooking scenarios, ensuring compliance with UL 217-8 and 268-7 standards by accurately distinguishing between real fires and nuisance particles like dust and steam.
Implementation Method 1
A photo-electric smoke detector works based on light reflection principals and generally includes a light emitter, a light receiver and an optic chamber
Implementation Method 2
when smoke is present in the optic chamber, the light receiver receives more light due to that light being reflected from the smoke particles
Implementation Method 3
utilizing different wavelengths and angles of light emission to discriminate between particle sizes based on Rayleigh scattering principles
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A smoke detector is provided and includes a housing defining a chamber receptive of ambient materials, one or more receivers disposed to receive light reflected from the chamber along one or more receiving axes, respectively, and multiple emitters disposed to emit light of multiple wavelengths, respectively, into the chamber at multiple angles relative to each of the one or more receiving axes, respectively, and a controller. The controller is configured to determine whether a current condition of the chamber should trigger an alarm based on output signals generated by the one or more receivers resulting from light emitted into the chamber by the multiple emitters being reflected toward the one or more receivers by the ambient materials.