Super Simple Sun Tracker.
Without using complex circuits and sensors, I was able to make my simple home-made Sun Tracker. This one only needs Solar cells, a motor and some gears. (11/20/2007)
I Got some solar cells since two months ago, but it wasn't until the last week I decided to put those solar cells to work. I really didn't have any good idea for it, I was thinking to use it to power toys or some homemade projects. Finally, I thought I can use those solar cells to charge rechargeable batteries.
Bad idea. Rechargeable batteries needs from 8 to 14 hours to get fully charged but using the solar cells in a fixed position, it only gets about 6 or 7 hours of direct sunlight. The solution: A sun tracker.
A sun tracker allows to get 9 to 12 hours of direct sunlight, enough to charge some batteries. I saw some sun tracker circuits long time ago but those are kinda complicated; sensors, fotoresistors, digital circuits, transistors, etc. As I just need something simple, I decided to build my own.
Here is how it works:
The sun appears every morning from the east. (Miracle!)
The sun dissapears every evening from the west.
So... the sun tracker should move from east to west, go back to east and move to west, again and again. That's all!
Here are the parts needed:
I did use some LEGO block and gears because it was handy. Any other pieces like meccano, knex or any other construction set works fine. This is only to give you an idea how I built my own.
There are two parts, the main base and the... the.. the other one that rotates. Call it whatever you want to call it.
The main gear is fixed to the base. It doesn't move.
The axle is also fixed to the gear. It provides support to... hmmm... to... that thing that rotates. Let's call it "the rotator".
This is my design of the mechanism. The speed of the rotation is reduced by the gears and slows the movement. We don't want the solar cell to fly away when the sun tracker rotates at 5,000RPM, right?
Now it's time to install the solar cells. The small one provides power to the motor. It is connected directly to the motor. No sensors, No transistors, no fancy circuits.
There is an aluminium foil covering one side and the top of the small solar cell (just 1 inch by 5/8"). It is installed almost vertically. I will explain the reason of it later.
The Main solar cell is the bigger one. I did install it in a 40 degree angle just as example. I think ideal angle is 60 degrees. Under that solar cell the rechargeable batteries will be installed (not showed in the photo). I guess is not a good idea to expose the batteries directly to the sunligh.
This is my sun tracker working. The sunlight was so bright that, actually, the motor was working without stop. As you can see on the photo, I did put a cardboard to cover the small solar cell and "calibrate" the light on the circuit.
Here is how it works:
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 tracker.
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 gets 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 solar tracker.
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 it.
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