Archive: https://archive.today/XHWzV From the post: >>For most of the Arduino tutorials you will find on this website, power is usually not an issue as the Arduino is powered by the USB cable coming from the computer. However, sometimes you want to build systems that are going to be autonomous and powered by a battery. For example, you want to power a wireless motion detector just by using a set of batteries. The first idea would be to connect directly an Arduino board like the Arduino Uno R3 to a battery. Easy, right ? Well, it would work, but your battery would be depleted in a matter of days because some components like voltage regulators are always sucking power. So we need something better.