NooTrix submitted us a 4-part tutorial to build a Lego Mindstorm Elevator controlled by an Arduino Uno:

 The elevator is built using components from an old Lego Mindstorms RCX 1.5. For the control part, we use an Arduino Uno board instead of the obsolete Lego RCX brick. The motor and sensors are from Lego. The connection to motor is done using a set of transistors organized in a H-Bridge.

The goal of the project is to show how to control Lego parts (motor, sensors, …) using an Arduino:

the elevator carries a smartphone and keep it level which is useful for taking snapshots of documents instead of scanning them. Full description, a step by step tutorial, as well as pictures, videos are available online.

All circuit schematics and source code are released under a free open source license (creative commons).