Although using sun-trackers are not mandatory in PV systems, their application improves the efficiency and maximizes daily collected energy. To maximize collected energy from an on-board PV array, on a solar assist plug-in hybrid electric tractor (SAPHT) a sun-tracking system was designed and installed. Considering the mobile structure above the SAPHT, designing a time and date independent sun-tracker was desirable. Using four light dependent resistive sensors a sun-tracking system on a mobile structure was constructed and evaluated. Using the designed sun-tracking system, the experimental tests illustrated that 30% more energy was collected in comparison to that of the horizontally fixed mode. Only 1.8% of all maximized energy is consumed by actuators of the designed tracking system. However, the developed sun-tracking system is robust and inexpensive and showed acceptable performance during experimental tests.