connecting Duemilanove to 12 volt, 12 amp battery

Were working on a project were we need to power the arduino with an external power supply, it says that the recommended voltage range is 7 to 12 volts. We are using 12 volt, 12 amp batteries to power the motor and we were wondering what would be the danger in connecting the arduino to this same power supply.

From what i've found so far i think the arduino only draws the current that it needs so i believe the current isn't an issue, am i right?

We also need to power the osmc, from robot power, which needs 12 Volts and once again it should only draw the current that it needs to operate right?

So that's my main concern is how do i know that it will only draw the current it needs and not too much to fry the board and are there any other solutions that we can try using.

you are correct. current is something that is drawn, not given. things will only draw the current they require (not including things like led's which is why they use limiting resistors). the only thing you might have to worry about would be noise on the power supply. adding a few capacitors to your arduino's 5 volt line might not be a bad idea.

how do i know that it will only draw the current it needs

Because Mr. Ohm discovered a law that says so, so they named the law after him ;)

Think about it, you can plug a tiny little nite light into an AC outlet or you can plug a large vaccum cleaner into the same outlet, same voltage. Is there harm done to either?

Lefty