Here is a solar tracker system that tracks the sun’s movement across the sky and tries to maintain the solar panel perpendicular to the sun’s rays, ensuring that the maximum amount of sunlight is incident on the panel throughout the day. The solar tracking system starts following the sun right from dawn, throughout the day till evening, and starts all over again from the dawn next day.
 
Refer Blog for more details. https://www.dofbot.com/post/arduino-based-2-axis-solar-tracking-using-ldr 
 
 
Demo video:
https://www.youtube.com/watch?v=VFZ_wsTKK-s