Beginner questions

And yet another step closer to beginning with robotics!
I'm strumbeling upon another problem: The dc motors have 1,5V, the beagleboard 2.7 using ogt usbt (automatically) or 5V using the power connector and the arduino board uses 7V.

How can I use thesame power source? Using those thingies: RobotShop | Robot Store | Robots | Robot Parts | Robot Kits | Robot Toys ? As there are only 2 wires with a DC, how does this work? Or http://www.robotshop.com/sfe-logic-level-converter.html ?

Thanks again.

Cheers,
Stijn