I want to start playing around with motors, gears, and things like that. I would like to build some basic devices that I can control with microcontrollers. I have looked around at sets for building things... erector, lego, etc. But I haven't found anything acceptable; lego is close with gears, rods, pulleys, etc. available, but it's too toyish for me. What are some kits that I can buy to play with and build things?