研究目的
To present a methodology for integrating a light sensing device inside a lamp, using low cost circuitry to mitigate interactions between high power LED sources and sensing photodiodes, and to allow visual light communication among sources.
研究成果
A methodology to allow simultaneous Ambient Light Sensing and Visual Light Communication inside a simple LED lamp has been presented. It is applicable independently of lamp power and type. The current solution demonstrates feasibility even in small spaces, with potential for further improvements in modulation techniques and integration of other kinds of sensors.
研究不足
The current solution is able to transmit 100 or 120 bit/s, depending on the frequency of main lines. Communication distance depends directly from the power of lamps. The introduction of more sophisticated modulation techniques could increase bandwidth and reliability of communication.
1：Experimental Design and Method Selection:
The methodology involves designing a control and sensing unit interposed between the Power Supply Unit (PSU) and the LEDs to allow accurate Ambient Light Sensing (ALS) and Visual Light Communication (VLC).
2：Sample Selection and Data Sources:
A photodiode with an integrated optical ?lter is used as the light sensor, which acts both as a sensor for ambient light and as a receiver for optical signals.
3：List of Experimental Equipment and Materials:
The setup includes a photodiode, transresistance ampli?er, instrumentation ampli?er, sample-and-hold, band-pass ?lter, microcontroller (MCU), and modulator block.
4：Experimental Procedures and Operational Workflow:
At each cycle of the AC line input, the LEDs are turned off for a short interval centered around the zero crossing of the sinusoidal input waveform. A sequence of samples is gathered and stored for further calculations.
5：Data Analysis Methods:
The actual value of measured luminance is obtained by averaging the samples acquired while LEDs are off. For VLC, a differential approach is used, comparing the amplitude of signals at the frequencies corresponding to '0' and '1'.
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