This work presents a low-power small-size power-based solar tracking and energy harvesting system in cm-scale for solar-powered IoT devices. The proposed mini solar tracking system (mini-STS) uses a two-axis tracking mechanism with a hill-climbing power tracking algorithm to maximize the energy harvested. The boost converter is designed to convert the energy from solar source to charge batteries and achieve maximum power point tracking. Different from a large-scale STS, the mini-STS can significantly improve the collected power with reduced size and tracking accuracy, which is also good for low power design of the system. The mini-STS hardware demonstration verified the balance of the motor step sizes, wake-up intervals, power consumption and output power. Finally, the system prototype delivers approximately 40% output power improvement compared to fixed solar panels. By auto-fitting the data, it achieves a date error of 7 days and a latitude error of 3° for the prediction of the future sun trajectory.
