Analog Hot Surface Re-ignition Controller for Gas Appliances
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Solution Overview
Problem
Existing hot surface igniter controllers are expensive and unreliable due to complex microcontroller-based circuits that struggle in environmentally challenging and noisy environments, particularly in detecting flame loss and restoring flames within the required 4-second standard.
Innovation Solution
A hot surface re-ignition controller designed with entirely analog components, utilizing a triac to switch power via an isolation transformer, with positive feedback for rapid switching and encapsulation in epoxy resin to protect against current leakage, comprising a power supply block, flame detector block, signal amplifier and delay block, and triac driver block.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If microcontroller-based circuits are used for controlling the hot surface igniter, then the controller can achieve required functionality, but the circuit becomes expensive and unreliable due to complexity and environmental challenges
Solution Approach 1:
The patent replaces the electronic microcontroller-based control system with a purely analog circuit system using operational amplifiers, comparators, and timing components. This substitution eliminates the reliability issues associated with microcontrollers in noisy environmental conditions while maintaining the required control functionality through analog signal processing and comparison.
Solution Approach 2:
The patent uses inexpensive analog components such as operational amplifiers, comparators, and timing circuits that are cheaper and more reliable than microcontrollers. These components are designed to be simple, robust analog devices that can withstand the harsh environmental conditions without the complexity and failure modes of integrated microcontroller systems.
2Difficulty of detecting and measuring
If microcontroller-based circuits are used for flame detection, then the controller can detect flame loss, but the detection is unreliable and restoration time exceeds 4 seconds
Solution Approach 1:
The patent replaces microcontroller-based flame detection with an analog flame sensing circuit that uses a flame sensor to generate a voltage signal proportional to flame presence. This analog signal is directly processed by comparators and timing circuits, eliminating the delays and processing errors associated with microcontroller sampling and digital processing, thereby achieving reliable flame loss detection within the required 4-second restoration time.
3Adaptability or versatility
If complex circuits are used to achieve required functionality, then the controller can control power switching, but the circuit becomes expensive to produce
Solution Approach 1:
The patent replaces expensive microcontroller-based control circuits with inexpensive analog components including operational amplifiers, comparators, and timing circuits. These analog components are simpler, cheaper to manufacture, and require less sophisticated production processes, thereby reducing the overall production cost while maintaining the required power switching control functionality.
Solution Approach 2:
The patent extracts and eliminates the expensive microcontroller component from the control circuit, replacing it with a simplified analog implementation. By removing the complex digital processing element and retaining only the essential analog signal processing functions, the design achieves the required control functionality at a lower cost.
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 analog controller provides reliable and efficient flame detection and restoration, maintaining power to the igniter until a stable flame is detected for at least 5 seconds, ensuring robust operation in adverse conditions without electrical noise interference.
Implementation Method 1
the controller uses a triac to switch power to the transformer and incorporates positive feedback for switching the triac between on and off states in less than 1 cycle of the AC mains supply
Implementation Method 2
a capacitor is used to provide positive feedback from the triac driver block to the signal amplifier and delay block
Implementation Method 3
the power to the igniter is supplied via an isolation transformer
Implementation Method 4
the controller switches power to the igniter in response to a flame sensing signal from the igniter
Data Source
AI summary
A hot surface re-ignition controller for use with a transformer for powering a hot surface igniter in a gas appliance. The design includes flame detection circuitry for interfacing with flame detecting electrodes and is completely implemented in analog circuitry to provide reliable operation in harsh environments.