Solar Tracker parts for mini servos

thingiverse

Here are the pieces to make a Arduino solar tracker out of mini servos. Will point the gnomon to the brightest light. These servo holders where designed around the Tower Pro MG90S Servos, but sure will fit other mini servos. The gnomon is 3.150" tall, 1.100" square at base. Place (4) LDR's (light dependant resistors) in the Gnomon and control 2-axis servos by percentage of light each LDR receives. The gnomon shades the LDR's if not at the right angle. By reading the two axis (up-down and left-right) of the LDR's, make the servos move away from the LDR's with less light toward to LDR's with more light, until they all receive light equally. From the servo angles you can calculate the angle of the sun. If you wanted to get serious you could use Arduino board with GPS or Compass to get perfect angle and location on LCD. Following the sun at the proper angle makes solar panels much more efficient. Arduino board could run linier to control solar panel angles in real time. Instructions Instructables has wiring instructions and code for Arduino boards. But it was really easy to write my own code. ((Up Left + Up Right/2) - (Lower Left + LR/2)), absolute of answer is difference in angle between Up and Down. ((UL + LL/2) - (UR + LR/2)), absolute of answer is difference in angle between Left and Right. I found that the servos would keep moving around after you found the angle. I have not done it yet but wanted to write a bit of code to save the last few readings of LDR's and average them. If movement is more than set difference, then move the servos. That way you could limit servo movement until there was a difference you set in the value in the LDR's. This was a very cool project! Use small screws to mount servo arms to the servo mount and the gnomon arm. Holes will probably need drilled out to your size. Drill out holes for LDR leads to go through base. Push the LDR's into the holes made for them, hold with silicon if needed. Join one side of LDR's terminals together and the other side each with a single wire. That gives you one common hot wire and one wire from each of the LDR's. Bend wires at bottom of Gnomon giving room for the button in center of arm for gnomon mounting and slide wires through the holes in end of arm. I used shrink tubing to cover wires under gnomon. Use #4 screw to hold gnomon to arm through center.