Hello - I have an ATmega328 on a breadboard that runs some stopwatch code (displayed on 16X2 LCD). I'd like for this to run on batteries. I'm pretty new to this so, I'm looking for some advice and tutoring. As I understand it, I have a couple of options:
Plug in a 9V battery and use a LM7805 to reduce the input from 9v to 5v. I actually did this and it works. But, a 9v battery won't fit in the enclosure I plan to use.
Use 4 X AAA batteries (total of 6v) and use a low-dropout (aka "step-down" or "buck") voltage regulator like a MCP1702 to reduce the input voltage from 6V to an acceptable voltage limit. 4 x AAA batteries will fit in my enclosure.
Use 2 X AA batteries (total of 3v) and use a step-up voltage regulator like Pololu NCP1402, which will convert anything above .8v to 5v.
Which strategy is better? Start off with more batteries and drop the voltage down to an acceptable level -- or start with fewer batteries and boost the voltage to an acceptable level? Using I've read lots of things about using special batteries (NiMH, rechargeables) and not worrying about regulation. However, I can't guarantee that the users of the stopwatch will replace the batteries with specific batteries -- they might use NiMH or alkaline or whatever is available.
Thank you for the help!