Sang Hoon Lim

Development of an AVR MCU-based Solar Tracker

An embedded two-axis solar tracking system was developed by using AVR micro controller for enhancing solar energy utilization. The system consists of an Atmega128 micro controller, two step motors, two step drive modules, CdS sensors, GPS module and other accessories needed for functional stability. This system is controlled by both an astronomical method and an optical method. Initial operation is performed by the result from the astronomical method, which is followed by the fine controlled operation using the signals from Cds sensors. The GPS sensor generates UTC, longitude and latitude data where the solar tracker is installed. A database of solar altitude, azimuth, and sunrise and sunset times is provided by UART (Universal Asynchronous Receiver/Transmitter).

Transient and Synchronized Behaviors of Two Coupled Thermal Acoustic Converters

AbstractIntegration of multiple sound generators is essential to the development of large-scale, sono-assisted processes such as combustion, evaporation, or CO2 capture with acoustic excitations. In this work, the transient and synchronized behaviors of a thermal acoustic converter (TAC) pair were investigated experimentally for various crossing angles and different separation distances between the converters. The two TACs were acoustically coupled through the air mass between their openings, and the only mode-locking operation that could be achieved was the one that was nearly 180° out of phase. The time to achieve synchronization was found to be dependent upon the initial mistuning of the frequencies and the crossing angle between the converter axes. The synchronization process could also be accelerated by turning on the converter with the lower power input first. When the separation distance between the two converters exceeded a certain value, synchronization of the TAC pair could not be achieved. As t...