Published: June 18, 2018
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By: Quyen Vong, Cal Poly Pomona
Category: Electrical Engineering
The purpose of this project is to create a low-power solar charging station for mobile devices in remote locations. The proposal of this project is to save energy by using renewable energy such as solar power, when available, or battery, to charge devices rather than relying on power from the electric grid. This charging station would potentially be offered in city parks, hiking trails, and other outdoor environments. It was discovered that to create such a station, the team had to develop the appropriate circuits to implement overall functionality of the project. The project utilizes an Arduino Uno Rev 3 microcontroller to manage main operations within the overall circuit. The microcontroller is used to display information on an LCD screen, to monitor the voltages of both power supplies, to control switching between solar and battery as the voltage source, and to decide when to charge the battery with solar power. The solar panel acts as the primary power source that supplies power to the load when needed, while also charging the secondary power source, the battery. The battery supplies power to the load whenever there is no solar power available such as at nighttime or cloudy days. By using sensing circuits that are monitored by the microcontroller, the charge controller will be turned on and provide enough current to charge the battery to 14.4V. The microcontroller activates MOSFETs within the circuit by using a PWM signals to open/close a circuit and provide a path for current to the load. In order to allow safe connection of low voltage devices, a buck converter is used to step down high voltages from the solar and battery source. The load dropout regulator (LDO) ensures that devices are provided with 5V for charging. With the use of a universal serial bus (USB) the charging port allows for compatibility with several devices. The goal of this project is to also design the charging station as efficiently as possible, at a low cost, and to be compatible with any device that will provide charge in a timely manner.