Internet of Things (IoT) provides more and more adequate infrastructures for many applications and advanced services. This context promotes the ability to satisfy the growing demand for innovative measuring systems, increasingly popular with intelligent nodes, totally wireless, easy to install that require the least possible maintenance. This paper aims to contribute to the 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 Limit of Detection (LoD) threshold. The proposed system consists of a single photovoltaic transducer to harvest energy and simultaneously detect ambient light. 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 cm(2). Data communication is via Bluetooth Low Energy (BLE) and, the device can acquire energy and detect ambient light from 250 lux.