· Solar Tracker System Based on a Digital Heuristic Controller on 2011 by D. Kang, E. A. Martínez. This project present paper proposes a detection, orientation and tracking method based on a Digital Heuristic Controller, which activates the tracking device with photovoltaic panels so as to optimize yield. There are several proposals aiming at the same target, nevertheless this work aims at building a prototype with rising movement (elevation) up to 90° and azimuth up to 180°, which enables this device to adjust to any location in the planet, no need to refer to information on solar position along the day. This would position the tracking device here presented as an elevation azimuthal portable device, which can also be built with a “sleeping” mode so as to protect the tracker from strong winds.
· Improved Structure of Solar Tracker with Microcontroller based Control on 2010 by M. Amir Abas. It uses pulley and chain to rotate and turn the Solar Panel facing to Sun. The structure is quite complicated and fragile since normal PVC was used for main weight and stand. Shadow concept is applied for Solar Sensor which implements two LDRs. This technique is significantly good but will face gray decision when both LDRs not able to detect Sun. As a result, the system may face confusion when the area is fully covered by clouds. Another drawback is the autonomous decision is not practical due to the process of changing is very repetitive.
· A Microcontroller Based Automatic Sun Tracker Combined with a New Solar Energy Conversion Unit on 1998 by F. Huang. The system is activated when the panel voltage is higher than 40 V. The time interval to rotate the solar panel can be set at a desired value, say, 5 or 10 minutes. At the beginning of each interval, the panel is rotated first to p, position, then to p2 position. If the panel voltage, Vp, at p2 is greater than that at p1, then the panel is advanced further. Until the position where the open circuit voltage of the panel is less than the one at the previous position. The sun tracking is completed by rotating one position back, p3.