I wanted to add a Microcontroller to my Technic lego, but I can't afford Mindstorms or NXT right now, so why not add my Arduino?
I wanted a solution to adding motors that is non invasive, does not destroy any "prime" parts, and simple to use. This is what I came up with.
You will need for each interface:
1 2x2 tall Lego brick, any color
1 2 position screw terminal block
about 2" solid core wire, 22-24 AWG
Small drill bit or finishing nail
Diagonal cutting pliers, smaller is better
Fine tip sharpie
Step 1: Mark and Drill holes
Measure up the holes on one side of the brick by holding the screw terminal and mark holes as shown. Drill holes with small nail or drill bit. Drill holes in top 2 corresponding studs as well. You want these to line up as close as possible, but centered in the studs is good.