Battery-free visible light sensing

We present the design of the first Visible Light Sensing (VLS) system that consumes only tens of μWs of power to sense and communicate. Unlike most existing VLS systems, we require no modification to the existing light infrastructure since we use unmodulated light as a sensing medium. We achieve this by designing a novel mechanism that uses solar cells to achieve a sub-μW power consumption for sensing. Further, we devise an ultra-low power transmission mechanism that backscatters sensor readings and avoids the processing and computational overhead of existing sensor systems. Our initial results show the ability to detect and transmit hand gestures or presence of people up to distances of 330m, at a peak power of 20 μWs. Further, we demonstrate that our system can operate in diverse light conditions (100 lx to 80 klx) where existing VLS designs fail due to saturation of the transimpedance amplifier (TIA).