# How to power a 12v outdoor project with microprocessor?

Forgive me if this is a really basic question, but I'm still at the "consideration" stage of a basic LED project, thinking about lighting up one of those flexible LED strips from a microcontroller such as an Atmel AVR. But it'll be an outdoor gadget so it'll need to be run from batteries.

I've seen other questions specifically using car power and how to get a lower voltage from that, and other questions starting from a 3V supply and boosting it to 12V, but I'm not even sure which of those I want. Which would be better, starting from a 12V battery source (either 2*6V or even a real car battery?) and dropping it for the microprocessor, or starting from something lower (like AA batteries?) and boosting it for the lights?

The lights apparently need 12V, and the back of my envelope says they'll draw around 1A, which sounds a lot, multiplied by a few hours (say 3 or 4), so it seems that's far too much for AAs unless I connect a few handfuls of them. Also it would be nice if the batteries could be recharged easily (and I've no idea how to do that with a car battery!).

At the moment I'm assuming that getting the microprocessor to switch the strip(s) on and off is a separate problem, I'm just at the stage of thinking about the power, the two separate voltage levels, and whether the whole thing is feasible or not. Any help would be very welcome!

• What LEDs are you considering? Do you have a spec? Commented Apr 23, 2013 at 10:51
• Strips of red LEDs on a roll which is cuttable to various lengths. Voltage is 12V, and based on the strip lengths I think I need, I calculate a draw of about 1A. I need to check whether the strip can take a (little) bit of weather though. Commented Apr 23, 2013 at 11:24
• That's not a spec - how did you calculate 1A draw. You are interested in efficiency and life of the battery so this might be important when considering an answer. Commented Apr 23, 2013 at 11:36
• The data sheet says "max forward current 4.4A" and "Power dissipation 52.8W" for the whole roll. I'm not going to be using the whole roll, and not all of my strips will be on at the same time, so I came down to roughly 1A. Commented Apr 23, 2013 at 11:58
• Maybe a link to the data sheet? Commented Apr 23, 2013 at 12:01