研究目的
Investigating the use of commercially off-the-shelf LEDs, illuminated by the flashlight of a smartphone, as a contactless wake-up system for microcontrollers in sleep mode.
研究成果
The study demonstrates that commercially available LEDs can be used as photodiodes for a contactless wake-up system for microcontrollers. By adding a resistor in parallel with the LED, a better discrimination between the voltages corresponding to the signal of interest (flashlight) and the interfering lights is achieved. Red LEDs are more suitable for outdoor applications, while blue LEDs are better for indoor applications.
研究不足
The study is limited by the lack of information from LED manufacturers about the response of LEDs to light. Additionally, the dynamic characterization of the LEDs operating as photodiodes is still in progress.
1：Experimental Design and Method Selection:
The study involves the current-voltage (I-V) characterization of different kinds of LEDs for two scenarios: outdoors and indoors. The LEDs are illuminated by the flashlight of a smartphone, and the generated LED voltage is proposed as the wake-up signal.
2：Sample Selection and Data Sources:
Selected LEDs include 2 red, 2 blue, 1 green, and 1 white, with some chosen for higher emitting power levels. All LEDs have colorless-clear lenses and flat top lens style.
3：List of Experimental Equipment and Materials:
A precision source/measure unit (SMU B2901A, Keysight) was used for measuring the LED current while performing a LED voltage sweep. A smartphone (Motorola Moto X Style XT1572) was used as the reference for the flashlight.
4：Experimental Procedures and Operational Workflow:
The LED terminals were connected to the SMU, and for each LED and light source, the LED current was measured while performing a LED voltage sweep in steps of 100 mV. Additional characterizations were performed in darkness.
5：Data Analysis Methods:
The open-circuit voltage (Voc) and the short-circuit current (Isc) were calculated. The effect of placing a resistor in parallel with the LED was analyzed to increase the voltage difference between the flashlight and interfering lights.
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