posted on Dec, 23 2011 @ 10:58 AM
A couple of things to keep in mind...
Solar cells are not cheap (unless your company makes and sells them,of course). I managed to find a halfway decent deal on some cells about the size
he is using, surplus, a while back and they were still about $3 per.
The current output from a small cell is tiny. Panels use multiple cells arranged in parallel in order to increase the current, and in series to
increase the voltage. This means if you want four times the cell voltage and four times the cell current, you need 16 cells.
If you plan on continuing to use your phone indefinitely, do not use this procedure. It will charge a battery, yes, but it can also easily overcharge
a battery, shortening its life span considerably. Commercial battery chargers contain circuitry to detect when a battery is charged and shut off all
but the tiniest trickle of current to prevent this. Lithium-ion and NiMH cells are particularly sensitive to overcharging.
I noticed he mentioned the parts list, but never mentioned how to hook them up:
Each solar cell will have a positive and a negative side. You hook these up in an array, arranging them in series to obtain the desired voltage, and
each series then in parallel to get the required current. Voltage on a single cell is usually about 0.5V, while current is roughly proportional to the
area of the cell. So if you cut a cell that is rated for 10 mA current in half, expect to get about 5 mA current.
When you cut solar cells, be careful not to cut the main leads! Cut across the secondary leads.
Connect the positive lead from the solar cells to the positive lead of the capacitor, and the negative lead of the solar cells to the negative lead of
the capacitor. Capacitors have a lead marked; if you are not sure about the solar cells, connect them to a voltage meter. When the voltage reading is
positive, the black lead is negative.
A voltage regulator (that's an LM7805, btw) has three terminals. You'll need to identify them by the accompanying documentation if possible, but
normally the middle lead is the ground. One of the others is input; the other is output. If you're using trial and error, be careful not to leave it
hooked up backward too long. Those regulators are pretty hardy in comparison, but still can burn out.
Connect the ground to the negative solar panel/capacitor leads, the input terminal to the solar panel/capacitor positive leads, and the output
terminal to the USB (or whatever you are using for an output jack). You just built a power supply.
The regulators come in many different voltages, with the most common being 5V, 12V, and 15V (LM7805, LM7812, and LM7815 respectively). You will need a
couple volts difference between the input and the output terminal voltages... depending on the exact chip used, some regulators will not even turn on
until the minimum voltage level is reached, while others will just act like a small resistor until regulation is needed.
Cost: you can find a capacitor (I would recommend 470/500 uF minimum, and at least one and a half times the maximum voltage you might ever encounter)
in electronic equipment, or buy one at the local Radio Shack for under $5... less than a dollar mail order, but then you have shipping charges. The
regulator, about $2 at Radio Shack, 50 cents mail order. All of the cost is in the solar cells.
One more thing: if you plan on doing this, get a soldering iron, not a soldering gun! Bigger does not mean better when it comes to soldering!
25-35 watts is more than enough (I could do all that with my 12-watt precision iron). Also make sure you use rosin flux solder; acid flux will destroy