The Mechanism we have made have two rollers one is driving roller & another is driven roller. Driving roller is located on upper side of a solar panel structure along with motor attached to it.
Driven roller is located on lower side of solar panel structure along with breaking pad attached to it. Both the rollers are connected to each other via belt pulley mechanism. Cleaning tank is provided before the driving roller on upper side. Cleaning tank consist of two slits & supporting roller & water. The plastic sheet is passed through this driving, driven & supporting roller in the tank.When initially driving roller rotates it windup the plastic sheet passing through cleaning tank. As it covers the length equal to length of solar panel with some clearance the motor will stop & it will start rotating in opposite direction. Through the belt pulley drive lower roller will wind up the sheet to its initial position & then motor will automatically stop.