Flame Detector Using Silicon Photodiodes and Signal Processing

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Solution Overview

Problem

Existing flame detectors are costly and limited in their ability to distinguish fire from non-fire optical sources, often requiring specialized sensors and filters, and are not effective in sensing fires beyond burning hydrocarbons.

Innovation Solution

The use of low-cost nearband infrared and visible light photodiodes in conjunction with amplitude-based temporal signal processing algorithms to detect the presence of flames, allowing for reliable fire detection in indoor environments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If specialized sensors (lead-salt quantum sensors, thermopiles, pyroelectric sensors) and narrowband thin-film optical interference filters are used, then measurement precision and reliability of fire detection are improved, but device cost and complexity increase

Engineering Contradiction:

Improvefire detection precisionVSAvoidsensor and filter complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces expensive specialized sensors (lead-salt quantum sensors, thermopiles, pyroelectric sensors) with inexpensive silicon-based photodiodes. This substitution dramatically reduces device cost and complexity while maintaining adequate detection capability through software-based signal processing algorithms that compensate for the simpler sensor's limitations

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent replaces physical optical interference filters with software-based spectral analysis. Instead of using narrowband thin-film optical interference filters to separate wavelengths, the system uses digital signal processing on broadband photodiode output to identify fire signatures, eliminating complex optical filtering hardware

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If multi-sensor detectors with specialized sensors and filters are used, then reliability of distinguishing fire from non-fire sources is improved, but device cost increases

Engineering Contradiction:

Improvefire vs non-fire distinction reliabilityVSAvoidmulti-sensor system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes a single broadband photodiode perform multiple functions that previously required multiple specialized sensors. The photodiode detects multiple wavelengths simultaneously, and software algorithms process the broadband signal to identify different fire types and distinguish from non-fire sources, replacing multi-sensor configurations

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent changes the detection approach from using multiple sensors with fixed spectral responses to using a single sensor with software-based parameter analysis. The system varies and analyzes signal parameters (amplitude, frequency, temporal patterns) to achieve reliable fire detection and discrimination without additional hardware

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If specialized narrowband thin-film optical interference filters are used, then measurement precision for specific fire types is improved, but ease of manufacture and device cost worsen

Engineering Contradiction:

Improvespecific fire type detection precisionVSAvoiddetector manufacturing ease

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces expensive narrowband thin-film optical interference filters with inexpensive silicon photodiodes that have broad spectral response. The manufacturing process is simplified as photodiodes are standard semiconductor components, whereas narrowband filters require complex deposition processes and precise alignment

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent uses software algorithms to create virtual spectral filtering capabilities. Instead of physical filters that block certain wavelengths, the system digitally processes the broadband photodiode signal to extract fire-specific patterns, effectively copying the filter function in the digital domain

Inventive Principle:

Principle #26Copying

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

This solution provides a cost-effective and reliable method for detecting flames by using inexpensive silicon photodiodes and processing algorithms, effectively distinguishing fire conditions in controlled environments.

Implementation Method 1

visible light and near band infrared to provide prompt and reliable reporting of the presence of flames

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS9449485B2Flame detector having visible light related processing circuits and infrared related circuits respectively coupled to photodiodes to establish instantaneous dc related signal changes and peak-to-peak ac signals over a predetermined time interval

Publication Date: 2016.09.20 HONEYWELL INTERNATIONAL INC

AI summary

A flame detector incorporates visible and near infrared sensors in common with processing circuits to form processed instantaneous, dc type, signal values minus an average value and peak-to-peak ranges of values of ac-type signals over a measurement time interval on the order of three seconds. The resulting values are further processed to determine the presence of a fire condition by comparing them to a predetermined threshold.