I am building a system using an embedded board that appears to use about 1/4 to 1/3 AMP according to my bench power supply. Is this low enough power consumption for this system to be run off of some battery(s) charged by a solar panel no bigger than 3'x 3'?
EDIT: Why the down votes? Is it not a reasonable question? I'm not really an electrical engineer and I've never worked with solar panels before.
More details:
1- The board will be "active" for about 10 hours a day.
2- Board uses 5 volts.
3- I'm probably not understanding what my bench power supply is telling me about power usage. Each supply has an "AMP" reading in the form of X.XX and is currently reading about 0.22. I "assusmed" that meant the board is drawing nearly a 1/4 AMP. However the documentation for the board says typical power usage is about 250 mA.
4- The board is an Olimex SAM9-L9260 ( AT91SAM9260 ) that is sitting running Linux and sending output to a serial console as fast as possible ( counting ).
Best Answer
As you say, tough crowd, especially as you've done a bit of research into your actual power consumption.
Your device consumes 5V * 1/4A = 1.25W. Lots of solar equipment is available for use with 12V lead-acid batteries, as used in caravans, so let's assume that. Let's assume that you drive the device through a buck converter (switchmode power supply), so the current draw at 12V is about 100mA. Let's round that up to 125mA for headroom. You should allow at least 48h of operation (through dark days in winter), so you need at least 6Ah of usable capacity from the battery. Choose deep cycle gel batteries, although for this level of discharge a car battery will be an OK substitute if you have one lying around.
Now you need to size the charger. Allow twice as much charge into the battery as you expect out, for charging over an 8 hour period. 12 / 8 = 1.5A charge current. Note that this is a lot more than the drain current! That's 18W. So e.g. this is a little undersized, but the right kind of thing to be looking for. You could buy a panel and charger; whole thing should be under 1m^2.
Don't forget to align the panel optimally and weatherproof everything.