Schematic of the Arduino Solar Tracker Circuit. As you can see in the schematic all that you need to make the electrical part is the board, one servo, 2 LDRs and 2 x 10K resistors. Usually the servo ...

Of course the Arduino and motordriver dont find place in the standard housing they are glued in a box on the side of the servo. B.T.W you just dont tell it to go to zero after a 10 hour print :-).

This is what that control circuit measures in order to judge the position of the servo horn. He’s using 1.6k Ohm resistors in this demonstration. But he didn’t just drop them in willy-nilly.