SUNFLOWER Personal SOLAR CHARGER
By kyle gilbert
The Sunflower Solar Charger is a personal solar power station. It has a solar panel that is built to follow the sun, much like a sunflower. Simply place the unit in a sunny spot, and the unit is designed to track the sun, giving you the most efficient utilization of power.
The way this unit works is it tracks the sun all day long and charges an internal battery bank. The stored energy can be utilized to power a variety of USB devices.
For a brief presentation about this product click the video to the right.
introduction
block diagram
Here is a system diagram, showing the basic components for how the system will work.
Time management
This is a Gantt Chart that shows when I plan to work on different aspects of the project.
Critical Components
At the heart of this project, lies the LTC3129, a boost/buck voltage regulating chip. This chip will take the voltage from the solar panel, that can range from 3 to 8V and convert it to 5V for the purposes of charging the Li-Ion battery cell. The following is a link to view the specifications on their product.
http://www.linear.com/product/LTC3129
This is a schematic of how the LTC3129 will be wired
My approach for this project addresses professional, ethical and social concerns mostly in the areas of environmental conservation. This product will harness free energy and produce very little waste. In fact, the only waste created by this product will be when the NiCd batteries wear out, which can typically last 2,000 cycles.
This product can also offer free power to users. Energy costs are on the rise, and fossil fuels growing more rare, having the ability to utilize solar energy becomes more and more important to society.
Professional, ethical, social concerns and respect for diversity
The Arduino Uno is What was chosen to control the position of the solar panel. From an H-bridge that utilizes photo-sensitive resistors, it can determine where the sun is, and it drives a motor to point the panel at the sun.
The solar panel used for this project is a compact model capable of producing about 700mW of power. It is lightweight and easily packed away.
When in direct sunlight, this panel has been measured and produces 9V when pointed directly at the sun, which is what the Sunflower will provide for this panel, allowing for a lot of efficiency in a small package.
In order for the micro controller to determine the position of the sun, 2 photo resistors are placed in an H-bridge configuration with 2 large resistors to keep the current low. The photo resistors will be attached to the panel. When the panel is not directly facing the sun, it will create a difference in voltage between the two outputs. The arduino will take that information and position the panel so it is facing the sun.