HVAC AC Voltage Measurement Using Optical Pulse Conversion
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Solution Overview
Problem
Residential HVAC systems lack an effective and cost-efficient method to measure AC voltages due to the high cost and complexity of digital voltmeters, leading to inaccurate compressor starting and reliability issues.
Innovation Solution
A control system using a microprocessor and a circuit that converts sinusoidal AC voltage into a pulse voltage, measuring the pulse duration to determine the AC voltage, with calibration and optical isolation to ensure accuracy and safety, allowing for multiple voltage measurements without external voltmeters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital voltmeters or analog-to-digital converters are used to measure AC voltage, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces complex electronic measurement systems (digital voltmeters, analog-to-digital converters) with an optical-based measurement system. An optical coupler converts AC voltage into optical signals that are measured by a photodetector, substituting electronic measurement circuitry with optical signal transmission and detection. This reduces complexity while maintaining measurement capability.
Solution Approach 2:
The patent introduces an optical coupler as an intermediary between the AC voltage being measured and the measurement circuitry. The optical coupler converts electrical signals into optical signals, allowing the measurement system to indirectly observe voltage through optical intermediaries rather than direct electronic contact, thereby reducing system complexity and improving isolation.
2Ease of operation
If voltage sensing relay is used to detect compressor start, then ease of operation is improved, but measurement precision deteriorates due to fixed threshold and tolerance variations
Solution Approach 1:
The patent implements a feedback mechanism where the optical coupler continuously monitors the actual voltage across the start winding and provides this information back to the control system. The microprocessor uses this feedback to dynamically determine when the motor has started, adjusting the detection threshold based on actual measured voltage rather than relying on fixed relay thresholds. This feedback loop eliminates tolerance variations and environmental factors from affecting detection accuracy.
Solution Approach 2:
The patent transitions from static voltage threshold detection (fixed relay threshold) to dynamic voltage monitoring. The optical coupler system allows the control system to adaptively determine the start condition based on real-time voltage measurements, making the detection mechanism dynamic rather than fixed. This enables the system to handle voltage variations due to temperature, component tolerances, and other conditions.
3Device complexity
If voltage sensing relay is used for compressor start, then device complexity is reduced, but reliability deteriorates due to temperature variability and component tolerances
Solution Approach 1:
The patent replaces the mechanical/electromechanical voltage sensing relay with an optical-based measurement system. The optical coupler uses optical signals instead of electrical contacts to sense voltage, eliminating wear and improving reliability. The optical system is less sensitive to temperature variations and component tolerances, thereby improving the reliability of compressor starting detection while maintaining acceptable complexity levels.
Solution Approach 2:
The patent introduces an optical coupler as an intermediary that isolates the measurement circuitry from the high-voltage AC environment. This intermediary provides galvanic isolation while enabling voltage sensing, thereby improving reliability by preventing temperature and voltage spikes from affecting the control electronics. The optical intermediary is more stable and reliable than direct electrical sensing methods.
4Adaptability or versatility
If sophisticated controls with microprocessor are added to HVAC system, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent makes the optical coupler system serve multiple functions: it measures AC voltage, provides galvanic isolation, enables adaptive control, and supplies data to the microprocessor for intelligent control decisions. By making this single component multi-functional, the patent increases system adaptability without proportionally increasing complexity. The optical coupler becomes a universal interface between the electrical system and the microprocessor control system.
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 system provides accurate AC voltage measurement with high resolution and low cost, improving compressor starting reliability and system diagnostics, with calibration ensuring consistency across varying temperatures and component tolerances.
Implementation Method 1
an optical isolator having a diode portion and a transistor portion... with the optical isolator electrically isolating the first resistor network from the second network
Data Source
AI summary
A control system to measure a sinusoidal AC voltage in a heating, ventilation includes a controller and a circuit connected to the controller. The circuit generates a pulse voltage based upon the AC voltage. The pulse voltage has a pulse duration. The controller measures a measured pulse duration based on the pulse duration and determines the AC voltage based upon the measured pulse duration.