LightLink: Enhancing Smartwatch Sensing and Actuation Through Visible Light Communication
summary
System uses a smartwatch's ambient light sensor as a receiver and the screen as a transmitter, locating the ALS 9.5 mm from top edge and forcing responses by amplitude‑modulating a white LED between sensor and reference currents while keeping screen brightness low. A 30‑mA battery powers a watch case with connectors and charging contacts (30‑mA battery). Implementations include forehead body‑temp and breathalyzer sensors, button and tilt sensors, a color sensor for strips, plus an IR remote, 4×4 LED strap and vibration band; most expensive add-on $12. Hardware and toolkit are open source.
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