Optically Powered Battery-Free Portable Microsystem for WSN and IoT Applications

This paper presents an ultra low power all-optical portable battery-free embedded microsystem that can be powered and controlled by a smart mobile phone. The microsystem contains an ultra-low voltage microcontroller as the processing unit; and, it receives power via a mini-solar cell. The optically powered microcontroller reads the local sensor data and transmits it to the mobile phone via modulating the light of an LED. A custom optical communication protocol that is based on Pulse Period Modulation is designed for the system. An image processing based mobile application utilizing the built-in flash of the phone is also programmed for controlling the microsystem. The mobile phone application using the built-in rear-facing camera analyzes the modulated optical signal from the LED on the microsystem and extracts the transmitted data. Experimental results of various local temperature measurements are also given.