IR LED Emitter for Traffic Preemption with Current Control
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Solution Overview
Problem
Conventional traffic control preemption systems using strobe tube emitters are power-intensive, generate unnecessary light outside the infrared spectrum, and degrade over time, reducing their effectiveness and increasing the risk of emergency vehicles not clearing intersections promptly.
Innovation Solution
The use of infrared (IR) LEDs with a controller to maintain consistent IR radiant power through individual current control, reducing power consumption and enhancing reliability, while allowing for precise control of light pulses to activate traffic control preemption systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional strobe tube emitters are used to activate traffic control preemption systems, then sufficient radiant power can be generated to be detected from over 2500 feet away, but the system consumes excessive power and generates broad spectrum light including unnecessary visible light
Solution Approach 1:
The patent changes the fundamental operating parameters by switching from visible spectrum strobe tubes to infrared LEDs operating at wavelengths of 850nm or 940nm. This parameter change allows the system to emit light in the infrared spectrum that matches the sensitivity peak of the photodetector, eliminating the need for broad spectrum emission and reducing power consumption while maintaining detection effectiveness
Solution Approach 2:
The patent applies local quality by using an optical bandpass filter centered at 940nm with a 50nm bandwidth in front of the photodetector. This filter selectively transmits only the specific infrared wavelength emitted by the LEDs while blocking other wavelengths, ensuring that the detector responds only to the intended signal and rejecting background light interference
2Illumination intensity
If conventional strobe tube emitters are used, then high radiant power is achieved, but the emitters degrade over time reducing effectiveness
Solution Approach 1:
The patent replaces the expensive, short-lived strobe tube emitters with inexpensive, long-lived infrared LEDs. The LEDs have significantly longer operational lifetimes and maintain consistent output characteristics over time, eliminating the degradation problems associated with strobe tubes while reducing system cost
Solution Approach 2:
The patent incorporates a feedback mechanism using a photodetector to monitor the light signal from the LEDs. The system counts light pulses and can adjust or replace LEDs when output degradation is detected, ensuring consistent system performance over the operational lifetime and maintaining reliability
3Reliability
If optical filters are used to restrict detector sensitivity to near infrared spectrum, then interference from other light sources is minimized, but the system becomes more complex
Solution Approach 1:
The patent achieves multi-functionality by selecting infrared LEDs that naturally emit at wavelengths (850nm or 940nm) where background light interference is minimal. This allows the system to achieve wavelength-selective operation through the LED emission characteristics alone, making the optical filter optional or simplifying its requirements while maintaining interference rejection capability
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 IR LED solution provides consistent and reliable activation of traffic control preemption systems, reducing power consumption and maintaining effectiveness over time, ensuring timely clearance of intersections for emergency vehicles without the drawbacks of traditional strobe tube emitters.
Implementation Method 1
a light emitter includes a plurality of groups of infrared (IR) LEDs
Implementation Method 2
The controller is configured to trigger an IR light pulse pattern from the groups of LEDs
Data Source
AI summary
A light emitter for a traffic control preemption system. The emitter includes a plurality of groups of infrared (IR) LEDs and a power source coupled to the groups of LEDs. A plurality of controlled current sources is coupled to the plurality of groups of LEDs, respectively. A controller is configured to trigger an IR light pulse pattern from the groups of LEDs and maintain a first level of IR radiant power from the groups of LEDs using individual control of respective current levels to the groups of LEDs in response to current sense levels from the groups of LEDs. The pulse pattern and first level of IR radiant power activate preemption in the traffic control preemption system.