Solar Tracking Device
With the current energy crisis, any idea that can make renewable energy more efficient is welcomed. Solar energy has become increasingly more viable with solar panels becoming more cheap to produce. But even with these advances, the most powerful panels still cost quite a bit of money. For this reason, most panels rotate to follow the sun and ensure the most energy absorption. While several DIY projects for this idea exist, many are jittery or require to much voltage to power. My goal was to create an effective light tracking device on which I could viably mount some small solar panels.
This project is fairly simple. All I need to sense sunlight are a few simple photocells. These are mounted on a platform. Using the Arduino Uno to interpret the voltages at the nodes between these cells, I can effectively see which part of the platform has the most light. After determining where the most light is, the Arduino will tell a pair of servos which direction to turn. This allows the platform to follow light and avoid shadows.
Parts and Prices:
-Arduino Uno : $35
-2 HS - 311 Standard Servos : $8 each
-2 packets of photocells : $3 each
-Wire : $5
-Circuit Board : $2
Materials for Aparatus:
-Wood : $10
-PVC : $1
-Epoxy and electrical tape : $4
-Hinge : $1
Total Price : $70
I found that the logic required to follow light was fairly simple. I had two sets of photo cells which were set in series, one set on each side of the platform. These were each attached to yet two more resistors set in the middle of the platform.
The Resistors on Their Platform
By using the Arduino to read the voltages from each node in the two simple circuits, I was able to tell how much light there was on each part of the platform and could move the servos accordingly. So that part of the project was relatively simple. The difficult part was constructing an apparatus that would allow me to rotate the platform effectively. I ended up using a PVC pipe as the vertical axis and used the platform as my horizontal axis. Moving these with the servos was the difficult part, because one of the servos would have to be able to move with the other servo's motion. This would prove to be difficult. I ended up using a swivel for the Arduino attached to the platform and made the servo itself the base (see pictures), making it so that the servo would be moving rather than its gear on the end meant that I needed to make the gear stay still somehow. I thought that I had the answer in my epoxy, which is supposed to be able to hold just about anything, but it turned out I was wrong. Getting the epoxy to set correctly proved to be difficult, and made my final product move in only one direction.
Pictures and Video
If I were to redo this project, I would definitely spend more time on the apparatus and less time fooling around with the logic. Soldering, nailing, taping and glueing everything together should have come first. That being said, the project did a very good job of sensing how much light there was across the platform. This project was successful in that the motion of the servos was fluid and responded quickly to changes in lighting. It was also fairly efficient, since it only needed the 5V from the Arduino. Many cheap solar cells will give off around 1.6-2.0 V and I designed the platform to hold 4 of these. If I had mounted them, I could have powered the device and still had some power left over. However, this setup would only become cost effective (the mass production cost would probably be around $40-45) if there was much more power involved. Since I only used 4 input pins and 2 output pins on the Arduino, I think it is safe to say that I could have used a less powerful microprocessor to equal effectiveness.