JonnyA:
It's not clear to me why it would be especially wasteful to use the Arduino to regulate the voltage (I'm a biologist and can barely work my TV remote, so bear with me :)). So it would be more efficient to find a different DC-DC converter and use that--like a 12V-5V or 6V-5V? What is it about the Arduino volatage regulation that makes it inefficient compared to other methods?Thanks
Jonny
simple really
start with a normal regulator
you feed 12 volts in
take 5 volts out
so there's 7 volts across the regulator
let's say 100 mA current
that's 700 mW burning off in the regulator!
this is not a feature of the Arduino regulator
it's a feature of regulators
a switching regulator is smarter
uses electronic wizardry to only take what it needs to keep the 5 volts ouput
I would still seriously consider a 6 volt battery as the power source