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!
Best Answer
Using AA batteries is not practical if you need an ampere for several hours. Based on your level of experience (I'm guessing) a small 12-volt sealed lead-acid battery sounds like a good choice. There's no point in trying to develop a high-efficiency regulator for the microcontroller, so just use a linear voltage regulator. Keep in mind that the voltage from a 12V battery actually ranges up to about 14V so make sure your LEDs can handle that. Small chargers for 12V batteries are available at your local huge box store or automotive supply.