Particulate Detector Using Dual-Waveband LED Pulsing
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Solution Overview
Problem
Existing particulate detectors in smoke and fire alarms cannot distinguish between smoke and other airborne particulates like steam or dust, leading to false alarms.
Innovation Solution
A particulate detector using a radiation source that emits radiation in two predetermined wavebands with temporary overlap, allowing for the determination of particulate characteristics such as size, shape, density, and mass by analyzing the relative contributions of radiation in each waveband, and a processor to calculate amplitude ratios for identifying the particulates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single waveband radiation source is used, then the detector structure is simple, but the ability to distinguish between different types of particulates is lost
Solution Approach 1:
The patent combines multiple radiation sources emitting at different wavebands (e.g., visible and infrared LEDs) into a single integrated radiation source assembly. This merging approach enables the detector to distinguish between different particulate types by analyzing their scattering characteristics across multiple wavebands, while maintaining a compact and manageable structure through unified optical design and shared detection electronics.
2Measurement precision
If multiple radiation sources are used simultaneously, then particulate characteristics can be determined, but the emissions may overlap in time and frequency
Solution Approach 1:
The patent employs periodic pulsing of individual radiation sources in sequence rather than simultaneous continuous emission. Each radiation source is activated in turn for a predetermined period, allowing the detection element to capture scattering signals from each waveband separately. This time-division multiplexing approach enables precise measurement of particulate characteristics across multiple wavebands while avoiding signal overlap and simplifying the measurement and processing requirements.
3Quantity of substance
If radiation sources emit continuously, then sufficient radiation is available for detection, but the temporal overlap of emissions makes particulate identification difficult
Solution Approach 1:
The patent replaces continuous emission with periodic pulsing of radiation sources in sequential order. Each radiation source is activated for a predetermined time period, ensuring sufficient radiation intensity for detection during each pulse while maintaining temporal separation between different wavebands. This allows the detection element to capture adequate signal strength for accurate measurement while preserving the ability to differentiate waveband contributions through time-division multiplexing.
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 accurate differentiation between various particulates, reducing false alarms by determining the specific nature of airborne particles, thereby improving the reliability of smoke and fire detection systems.
Implementation Method 1
the radiation source comprises a light emitting diode for emitting radiation in the first predetermined waveband
Implementation Method 2
a detection element arranged to detect radiation from the sampling region at least first and second instances
Implementation Method 3
Detectors of this type rely on the concept of Mie theory, which can be used to explain radiation scattering by an isotropic sphere embedded in a homogeneous medium. For a particular wavelength of radiation, the angle of scattering is proportional to the size of the particulate from which the radiation is scattered.
Implementation Method 4
the radiation source further comprises a phosphor layer arranged to absorb at least some of the radiation in the first predetermined waveband, and to emit radiation in the second predetermined waveband
Data Source
AI summary
A particulate detector (10) comprises a radiation source (12) arranged to emit radiation in at least first and second predetermined wavebands towards a sampling region (18) suspected of containing particulates, and a detection element (14), shielded from the radiation source (12), and arranged to detect radiation from the sampling region (18) at least first and second instances. The radiation source (12) is such that the emissions in the wavebands temporarily overlap. The detector is such that, at the instances at which the radiation is detected, the relative contributions from the emissions in each predetermined waveband are distinguishable, thereby allowing characteristics of the particulates to be determined. The radiation source (12) may comprise a light emitting diode (24).