LED Retrofit Diagnostic System for Variable Message Signs
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Solution Overview
Problem
Existing Variable Message Signs (VMS) systems with halogen lamps face challenges in upgrading to LED lamps due to compatibility issues and the inability of retrofitted LED lamps to communicate failure statuses to the control side equipment, leading to potential sensing failures and increased maintenance costs.
Innovation Solution
A diagnostic system is installed between the control wiring and LED lamps, featuring a power supply and control circuit, LED driver circuit, and failure detection circuit, which generates a compensating load to mimic halogen lamp operation, detects anomalies, and isolates the diagnostic system from the controller upon failure detection, allowing the control side to register faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LED lamps are retrofitted into halogen lamp-based VMS systems, then energy consumption is reduced and lifespan is extended, but compatibility issues arise and failure status cannot be communicated to control equipment
Solution Approach 1:
A diagnostic system is introduced as an intermediary component between the LED lamps and the existing control equipment. This diagnostic system includes a power supply and control circuit that receives voltage from the control equipment, an LED driver circuit that powers the LED lamp, and a failure detection circuit that monitors system status. The diagnostic system translates LED lamp operations and failure states into signals compatible with the original halogen lamp control interface, enabling seamless retrofitting without modifying the control equipment.
2Ease of manufacture
If conventional LED lamps are used for retrofitting, then initial cost is reduced, but operating current is insufficient leading to sensing failures
Solution Approach 1:
The diagnostic system actively manages electrical parameters to ensure reliable operation. The power supply and control circuit receives voltage levels from the control equipment and transforms them into appropriate voltage and current levels for the LED driver circuit. The LED driver circuit then supplies the correct operating current to the LED lamp, ensuring it operates within specified parameters for both reliable illumination and accurate sensing by the control equipment.
3Reliability
If major components in LED driver circuit fail, then system reliability decreases, but automatic failure communication to control side is lost
Solution Approach 1:
The diagnostic system incorporates a failure detection circuit that continuously monitors the operation of the power supply and control circuit, LED driver circuit, and LED lamp. When a failure or anomaly is detected, the failure detection circuit generates a failure status signal that is communicated back to the control equipment through the existing control interface. This feedback mechanism ensures that control equipment is immediately notified of failures, enabling timely maintenance and reducing downtime.
Data Source
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AI summary
A system for diagnosing a fault in a halogen lamp-based variable message sign retrofitted with LED lamps is disclosed. The system comprises a power supply and control circuit, a LED driver circuit, and a failure detection circuit for detecting anomalies in voltage and/or current being supplied to the LED driver circuit. The system generates a compensating load such that current drawn by the diagnostic system and the LED lamp is within one or more limits predetermined by the external controller for maintaining operation of the variable message sign. The system is further provided with a controlled link connected to the power supply and control circuit. Upon an anomaly is detected by the failure detection circuit, the power supply and control circuit breaks the controlled link to isolate the compensating load from the external controller, thereby allowing the external controller to register a failure.