Power source is an important part because we’re going to have many boards/parts that need power and we no longer have the NXT Brick as a source..

To stay in the “Lego realm” a good solution is to use the Power Function battery boxes.

There are different battery boxes available in Power Function :

The basic one, using 6 AA batteries.	The new AAA battery box, using 6 AAA batteries. Which is a variant of the rechargeable one. (as you can guess, this version is much smaller and easy to fit than the first one)

The Power Function cable

So we need to customize a cable like this one:

When plug in the battery box, here what voltage we have:

So we can see that the :

• Green and Blue cables will always be on Ground and V+ regardless of the switch position.
• Yellow and Orange will be inverted depending of the position of the switch.

Making the cable

So, when you have one Power Function cable, you can make two power cables like this one:

The inner wires will be used to plug directly on a motor and the outer ones to plug on a board, like this: