Flat, rectangular panels can only be arranged in so many ways and always look industrial, boring, and out of place. So I decided to build a functional, but more aesthetically pleasing version of a USB solar charger.
I call my creation the "Solar Shrub". It's designed to resemble a round-leafed plant in a flower pot, but unlike a real plant, this one can charge my iPod, iPhone, and any other USB chargeable device!
I used eight 1.5 Volt round solar cells (leaves) attached to shrink-wrapped wires and clothes hangers (stems) to create an array capable of producing 5 Volts at about 300mA. I wired two sets of four cells in series (to get the voltage) and then wired the two arrays together in parallel (to get the current). I stabilized the power by building a 5 Volt Regulator circuit, then added an on/off switch, power LED, and female USB connector.
Now you can build one too! Just follow these instructions, then put it in sunlight, flip the toggle switch, and plug in your favorite USB device!
Step 1: Materials and Tools Used
1 - 7805 Voltage Regulator (Radio Shack #276-1770)
1 - Heat sink for the 7805 (Radio Shack #276-1368)
1 - Hea sink mounting hardware(Radio Shack #276-1373)
1 - Red LED(Radio Shack #276-041)
1 - SPST mini toggle switch(Radio Shack #275-0324)
1 - 22uf capacitor(Radio Shack #272-1026)
1 - .01uf capacitor(Radio Shack #272-1065)
1 - 220 ohm resistor(Radio Shack #271-1313)
1 - 4.7k ohm resistor(Radio Shack #271-1124)
1 - 3.3k ohm resistor(Radio Shack #271-1122)
1 - USB extension cable (Male to Female)
1 - Blocking Diode (1N4001)(Radio Shack #276-1101)
1 - Round Proto Board (Radio Shack #276-004)
Materials for Leaves and Stems:
8 - Round solar cells (hacked from solar garden lights) (Lowe's #379421)
8 - Wire clothes hangers
1 - Roll each of red and black 22 AWG wire (Radio Shack #278-1224)
2 - Pkgs of assorted shrink wrap (Radio Shack #278-1610)
10 - Small wire ties
1 - Can green spray paint
1 - 6" Clay Plastic Self-Watering flower pot (Lowe's #285869)
2 - Metal angle brackets
1 - CD
2 - Plastic standoffs(Radio Shack #276-1381)
Step 2: Building the Power Circuit
I used a round proto board to go with the round theme of the project, but you can just as easily use a square, boring board. I also decided to use jumper wires for the switch and LED so I could easily disconnect them from the circuit board after they were mounted to the flower pot. (What a strange sounding sentence.) You could just as easily hard-wire them to the board.
The circuit is a simple one based on the 7805 5 Volt Regulator with supporting components and a voltage divider to supply the 2 Volts mentioned above.
1. Solder the red wire (this will eventually connect to the positive terminal of the cell array) to the circuit board and to one side of a double-pin plug (for the power switch).
2. Solder in another double-pin plug for the LED and attach it to the open pin of the first plug.
3. Solder in the 220 ohm resistor, which connects the LED plug to ground.
4. Solder in the two capacitors. C1 is polarized so be sure to configure it correctly.
5. Solder in the voltage regulator.
6. Solder in the two resistors, which make up the voltage divider circuit.
7. Cut the USB cable about 6-8 inches from the female end and strip away the insulation and shielding
8. Attach the four wires of the USB cable to the circuit board.
9. Attach the black (GND) wire and create a "ground bus" across the back of the circuit board to link all components.
10. Solder jumper wires w/ female connectors to the switch and LED. Remember to slide some shrink wrap onto the wires before soldering. I've found it's really hard to get it on there afterward!
11. Test the circuit. I like to test things as I go along instead of waiting until the thing is all together. So I attached a 9 Volt battery to the red and black wires and tested the circuit with my iPod. Success!!!
Step 3: Assembling the Base
I wanted the electronics to be somewhat protected from the elements so I decided to use a CD as kind of a false floor. I mounted the circuit board (upside down) to the bottom of the CD using plastic standoffs. The red and black wire that connect the circuit board to the solar array pass through the center hole of the CD. I also added felt strips around the base to support the CD.
I drilled two more holes in the CD so I could later mount the leaves and stems to the top of it.
Step 4: Hacking the Garden Lights
They were pretty easy to disassemble:
1. Remove the battery
2. Take out three screws
3. Cut a few wires
4. Pry the cells loose from underneath.
I did this 8 times, of course.
I tested each cell under load to make sure it provided approximately 1.5 Volts.
Step 5: Building the Leaves and Stems
Step 6: Attaching Stems to the Base
After I had all of the stems mounted, I wired the cells together in a series-parallel circuit as shown in the schematic. Then, I added a blocking diode to the positive (red) lead. This prevents reverse current through the cells when there is no sun light.
Step 7: Putting It All Together
The stems are rigid enough (thanks to the 22 AWG wire and the clothes hangers) that you can bend them into any arrangement you like. You can also tilt the cells in any direction you wish; toward the sun for example.
As you can see from the final photo below, IT WORKS!!! I'm now able to charge my iPod, iPhone, and other USB powered devices while enjoying the sunshine!