A paranoid question about external power

This is probably a rather simple question, but I'd like some advice from an Arduino expert.

I've been running 2 led strips, each drawing about .2 A, from a 12 volt battery and interfacing with Arduino through a ULN 2003. This is all working splendidly.

Thus far, the the board has been powered through the USB but I need to power the Arduino either through the same 12 v batteries (which provide 1.3 Ah) as the LEDS OR power the whole thing from a wall wart.

I understand that for both, I have to make sure the 12 volts is regulated, and that I can use the Vin pin to supply power to the lights.

It seems to me like either one of those options would work out ok, how can I be 100% sure I won't fry anything?

Thanks!

You can just connect the 12V battery to the external power on the arduino too, without changing the way you power the led strips right now.

Neither the Arduino nor the LEDs need you to provide a regulated power supply, the Arduino because it has an on-board regulator, the LEDs because they don't really care as long as there is "enough" volts.

Awesome, thanks for you replies. If I do decide to run everything from the wall would you recommend using an additional voltage regulator?

Also if you guys want to see the project its going to be in Los Angeles this weekend:

proofsofconcept.com/misc/mirrorbox_flyer.jpeg