A Self-powered Ambient Light Power Measurement Platform with Time-domain Readout

Internet of Things (IoT) provides more and more adequate infrastructures for many applications and advanced services. This scenario promotes the ability to satisfy the growing demand for innovative measuring systems, increasingly popular consisting of intelligent nodes, totally wireless, easy to install, and that requires the least possible maintenance. In this context, this paper aims to contribute to state of the art with an energy-autonomous and battery-free measurement platform designed to measure the ambient light power when its level exceeds the sensitivity threshold. The measurement platform utilizes a single transducer to scavenge energy and concurrently measure the ambient light intensity. The result is a wireless measurement platform, which requires neither a battery nor a specific ambient light sensor, with the immediate advantage of achieving greater energy efficiency and using fewer components. The device implements off-the-shelf components on a printed circuit board (PCB) with a tag size of 2 x 2 cm2. Bluetooth Low Energy (BLE) implements radio implements device connectivity. Experimental data show that the device can acquire energy and detect ambient light with a limit of detection (LoD) of 250 lux and accuracy below 12%.