LED Bulb Ambient Light Sensing via Periodic Cycling
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Solution Overview
Problem
Ambient light sensing systems in lighting control systems struggle to accurately measure ambient light levels due to the high frequency or constant DC voltage output from modern lighting electronics, particularly in LED-based bulbs, which overwhelms any light sensor incorporated into the bulb.
Innovation Solution
A method where a solid state light fixture drives its light source with a cyclical signal to repeatedly turn the light on and off, allowing a light sensor to measure ambient light during the 'off' periods, ensuring accurate measurement without saturation from the bulb's own light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light sensor is incorporated into the bulb to measure ambient light, then ambient light measurement capability is improved, but the light sensor becomes overwhelmed by the bulb's own light output and cannot accurately measure ambient light
Solution Approach 1:
The patent applies periodic action by cycling the LED light source on and off at a frequency above human perception (e.g., >100 Hz). During the off-periods, the light sensor can measure ambient light without being overwhelmed by the bulb's own output. This periodic switching resolves the contradiction by creating time windows where the harmful light output is absent, allowing accurate ambient light measurement while maintaining continuous illumination perception.
2Measurement precision
If the light source is turned off to allow ambient light measurement, then measurement accuracy is improved, but the light fixture appears to be off to users
Solution Approach 1:
The system uses periodic switching of the light source at frequencies above human visual perception threshold (e.g., >100 Hz or >200 Hz). This creates the perception of continuous illumination while actually providing periodic off-states for measurement. The high-frequency cycling resolves the contradiction by making the intermittent illumination imperceptible to humans while enabling accurate ambient light sensing during the brief off-periods.
Solution Approach 2:
The patent maintains continuous useful action by keeping the light source cycling on and off at high frequency, which creates the perception of continuous illumination. The measurement function is integrated into this continuous cycling operation, occurring during the off-periods without interrupting the overall illumination function. This resolves the contradiction by maintaining perceived continuity while enabling periodic measurement opportunities.
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
Enables accurate ambient light measurement by the light fixture, allowing for effective control of light sources based on ambient conditions, including natural and other external light sources, without the need for external communication links among bulbs.
Implementation Method 1
measuring, via a light sensor in or on the light fixture, ambient light during times when the light source is off
Data Source
AI summary
A method for a light bulb or fixture to emit light and measure ambient light. The method includes driving solid state light sources, such as LEDs, in the bulb with a cyclical signal to repeatedly turn them off and on, where the light sources are turned off and on at a rate sufficient for the bulb to appear on. The method also includes measuring ambient light via a light sensor in or on the bulb during at least some times when the light sources are off, and outputting a signal related to the measured ambient light. In some cases the light sensor saturates when the solid state light sources are active and measures the ambient light level when the solid state light sources are not active. The ambient light level signal can be used to control when the light bulb is on and an intensity of light output by the bulb.