Smoke Sensor Dual Light Receivers Temperature Drift
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Solution Overview
Problem
Conventional smoke sensors face challenges in accurately detecting smoke density due to uncorrected errors caused by temperature changes and LED light emission variations, leading to incorrect smoke detection and increased complexity in correction methods.
Innovation Solution
A smoke sensor design featuring a light-emitting device, two light-receiving elements with one exposed to smoke and the other to zero smoke density, and a shared amplifier section to minimize output differences caused by temperature and LED variations, allowing for accurate correction of errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single light-receiving element is used to detect smoke, then the device complexity is low, but the measurement precision deteriorates due to uncorrected errors from temperature changes and LED variations
Solution Approach 1:
The detection function is segmented into two separate light-receiving elements: one exposed to smoke (first light-receiving element) and one shielded from smoke (second light-receiving element). This segmentation allows independent measurement of smoke-affected light and reference light, enabling error correction through comparison while maintaining relatively simple device architecture.
Solution Approach 2:
The second light-receiving element acts as an intermediary reference that measures the effects of temperature changes and LED variations without being affected by smoke. By introducing this reference element, the system can distinguish between errors caused by environmental factors and actual smoke density, thereby improving measurement precision.
2Measurement precision
If correction methods such as adding thermistors or multiple detectors are implemented, then the measurement precision improves, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the reference measurement function into the existing detection structure by using a second light-receiving element that shares the same optical path and electronic circuitry as the first element. This merging approach allows error correction without requiring separate correction circuits or additional temperature sensing components, thereby improving measurement precision while maintaining ease of manufacture.
Solution Approach 2:
The system uses its own second light-receiving element to automatically compensate for errors in the first light-receiving element's measurements. By comparing the outputs of both elements, the system self-corrects for temperature drift and LED variations without requiring external calibration or complex correction algorithms, thus improving precision while keeping manufacturing simple.
3Reliability
If conventional correction methods are used, then specific errors (temperature or LED deterioration) can be corrected, but errors for which no cause is identified cannot be corrected
Solution Approach 1:
The system implements feedback by continuously comparing the output of the second light-receiving element (reference) with the first light-receiving element (smoke detection). The difference between these signals provides real-time feedback about environmental variations, allowing the system to correct errors dynamically regardless of their specific cause, thereby improving reliability without requiring complex error identification logic.
Solution Approach 2:
The second light-receiving element serves multiple functions: it acts as a reference for temperature correction, LED deterioration compensation, and general environmental variation monitoring. This universal reference approach enables correction of various types of errors with a single simple mechanism, improving reliability while avoiding the need for separate correction systems for each error type.
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 enables precise smoke density detection by reducing output variations due to temperature and LED changes, improving detection accuracy and simplifying the sensor configuration, while reducing manufacturing costs.
Implementation Method 1
a light-emitting device emitting light
Implementation Method 2
a first light-receiving element receiving light which has traveled in the first chamber after being emitted from the light-emitting device directly to the first chamber or light which has traveled in the first chamber after being emitted from the light-emitting device and entering the first chamber through only a place having a density of smoke of zero
Data Source
AI summary
In a smoke sensor, a first light-receiving element which receives light from a light-emitting element and is disposed in a position where the quantity of received light changes according to a density of smoke and a second light-receiving element which monitors the quantity of light of the light-emitting element are arranged symmetrically with respect to the light-emitting element. Furthermore, a signal from the first light-receiving element and a signal from the second light-receiving element are amplified by an identical amplifier circuit. In a microcomputer, the density of smoke is computed based on a difference between an output obtained by amplifying an output of the first light-receiving element with the amplifier circuit and an output obtained by amplifying an output of the second light-receiving element with the amplifier circuit.