Photocontroller Ambient Light Detection Without Flicker
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Solution Overview
Problem
Conventional photocontrollers for outdoor luminaires struggle to accurately detect ambient light levels due to interference from the luminaire's own light output, leading to flickering and improper on/off switching during dusk and dawn periods, and require an external window for daylight detection.
Innovation Solution
A photocontroller with a photosensor, such as a photodiode or phototransistor, positioned inside the luminaire to measure external ambient light levels without interference from the luminaire's light, using an optical filter to absorb or reflect shorter wavelengths and a microcontroller to determine the light level signal and control the luminaire's operation, including recalibrating a real-time clock for accurate day/night control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional photocontroller uses an external window to detect ambient daylight, then the luminaire can be turned off during the day, but the luminaire's own light reflects off the window and interferes with accurate ambient light detection during dusk and dawn
Solution Approach 1:
The patent divides the detection function into two separate photosensors: one positioned to detect ambient light through the light output window (affected by luminaire light), and another positioned to detect ambient light without being affected by luminaire light reflections. This segmentation allows the system to use the appropriate sensor depending on operating conditions, resolving the contradiction between needing ambient light detection and avoiding light reflection interference.
Solution Approach 2:
The patent introduces an intermediary component (the second photosensor positioned at a specific location) that mediates the detection of ambient light without being subject to the harmful reflection effect. This intermediary sensor provides a clean ambient light signal that is not contaminated by luminaire light reflections, solving the measurement accuracy problem.
2Ease of operation
If the photocontroller relies on ambient light levels during dusk and dawn, then the luminaire can automatically switch on and off, but fluctuating light levels cause the luminaire to flicker and repeatedly turn on and off
Solution Approach 1:
The patent implements feedback control by continuously monitoring ambient light levels with the second photosensor (which is not affected by luminaire light) and using this stable feedback signal to control the luminaire switching. The microcontroller processes this reliable feedback to determine when to switch the luminaire on or off, preventing the flickering that occurs with unstable light level readings during twilight periods.
Solution Approach 2:
The patent changes the detection parameter by using a photosensor that detects ambient light at wavelengths where the luminaire does not emit light, or by using an optical filter to block luminaire wavelengths. This parameter change (detecting at different wavelengths) allows the system to maintain reliable automatic control without being affected by luminaire light, thereby eliminating flickering during twilight.
3Device complexity
If the photosensor is positioned to detect light through the light output window, then the structure is simple, but the luminaire light reflects off the window and prevents accurate detection of low ambient light levels
Solution Approach 1:
The patent segments the photosensor positioning into two configurations: a first photosensor positioned to detect light through the light output window (simple structure but affected by reflections), and a second photosensor positioned at a different location (more complex structure but immune to reflections). The system can select or combine these configurations based on the specific application requirements, resolving the contradiction between structural simplicity and measurement precision.
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 solution enables stable day/night control without external windows, prevents flickering, and maintains accurate light output control by detecting ambient light levels independently of the luminaire's light, ensuring proper operation during fluctuating light conditions and power failures.
Implementation Method 1
using an optical filter to absorb or reflect shorter wavelengths
Implementation Method 2
A photodiode, phototransistor, photo-integrated circuit, or other photosensor, is positioned such that light from outside of the luminaire falls upon a sensitive area of the photosensor
Data Source
AI summary
A system to control solid state light sources, including a photosensor responsive primarily to wavelengths of light outside the emitted light band of wavelengths that the solid state light sources emit when the solid state light sources are in the ON state, and which produces a light level signal representative of a level of sensed light primarily for wavelengths outside of the emitted light band of wavelengths. A set of circuitry receives the light level signal representative of the sensed level of light from the photosensor, determines a contribution by the solid state light sources to the sensed level of light, and uses a compensated light level or a compensated threshold in assessing a dusk condition or a dawn condition when the solid state light sources are in the ON state to compensate for the contribution by the solid state light sources to the sensed level of light.