The Arduino boards can supply power in two ways:
We already used USB for supplying power to the Arduino since the beginning of the section. This is a pretty nice way to begin (and even to make a great project). This is easy and works for many purposes.
We can also use an external power supply when we need more autonomy and mobility with our Arduino devices.
In any case, we have to keep in mind that both our Arduino and our circuits wired to it need power. Usually, the Arduino consumption is no more than 50mA. Add some LEDs and you'll see the consumption increase.
Let's check some cases of real use.
Why and when would we use a USB power ...