The objective of this lab was to design, build and implement a solar cell array tracking system. Our system worked by using a photocell attached to a stepper motor to find the angle with the highest intensity of light. The stepper motor was programmed to step at a certain resolution and with each step it recorded a reading of the light intensity with the photo-resistor. After it had stepped through al angles that the solar cell could physically point towards, it output the stepper position where the max light intensity was found. This was then converted into an angle. The angle recorded from the orientation of the photo-resistor at the position of the limit switch, to wherever the maximum light is.

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     Once this angle was know we used a DC motor, that is attached to a potentiometer and a solar cell by a shaft, to move the solar cell to the angle with the highest light intensity. We were able to do this by pulsing the dc motor, and finding the output voltage of the potentiometer. This output voltage represented a certain angle, and the voltage was converted into this angle. The DC motor would continue to pulse and after each pulse, a new angle was read into the Arduino by the potentiometer. We did this until we were within a certain distance from the desired angle. Therefore, this apparatus was accurate up to 5 degrees. Once the desired angle was reached, the photo-resistor would scan the room again and update the new optimal angle to the DC motor apparatus. This closed control loop would work continuously until the apparatus is disconnected from power.

 

     All of these components were connected to an Arduino board with a motor shield attached to the top. We applied an Arduino code that allowed to us to find the angle with highest intensity and move the solar cell to this angle. A limit switch was also applied to the stepper motor part of the device, this limit switch was used to move the stepper motor all the way to the beginning of its cycle so that the motor could move through its cycle again.

 

     Our device worked very well, to the point that when a light most intense at a certain angle the photocell recorded this angle and moved the solar cell to the angle with highest light intensity. This process can be seen in the video below (this is at 4x speed)