The small cell
provides power to the motor directly. If there is no sun, or night, the
motor is not going to work. The cardboard covers the cell to ensure the
motor will turn on ONLY when there is enough light to move the sun
The foil covers the
top and the left side of the small cell to provide shadow to it. When
the small cell is on the shadow, the Main solar cell is getting direct
sunlight. Those solar cells are installed in a 90 degrees direction.
If the sun moves to
the west, the small cell will get light and powers the motor until the
aluminium foil's shadow turns it off. In the evening, When the sun
hides, the sun tracker will not move, the main solar cell will be
facing west, the small solar cell will be facing north.
The next morning,
the sun will rise from the east side. The sunlight will be reflected by
the aluminium foil to the small cell, so the sun tracker will turn to
the other side; east. This cycle repeats again and again.
Let's say, there is a big cloud and there is no sun for some hours, What is going to happen?
When the sunlight comes back, it will be directly to the small solar
cell, so it will locate immediately the position of the sun.
What if there is no sunlight all day long?
It doesn't matter. The aluminium foil and the alignment of the solar
cells allows to turn it on even if the sun comes from the back of the
What if there is a tornado? Forget about the sun tracker! RUN! GET COVER!
What if I don't want to the sun tracker to rotate?
That can be solved using some pulleys and weights to make it turn back
when there is no sunlight. When there is light, the motor will pull the
pulleys and weights and hold it (with low current). If the sun hides,
it will face back east but I will locate the sun again as soon the
sunlight comes back. I didn't built this version yet. So try to imagine