I got those lego minstorms that you can program to do whatever you want, I just made a photocopier entirely out of the legos that were included except for a Q-Tip I used as the printing pen. Basically there's the light sensor and a motor holding the Q-tip both on a cradle that moves from left to right, whenever the light sensor sees dark, it makes the motor lower the Q-tip on the paper. One problem is because of how I programmed it, it can't copy horizontal lines, that's why the bottom of the house in the copy is missing, I'll have to improve the program that controls it.


Video (1 MB):
http://auctionautobidder.com/legocopy.mpg