Version 2 with lots of improvements :-)
A whimsical toy train chugs along powered by magnets...and LittleBits. The entire project fits within a small wooden box which also serves as the platform for the train.
The box is a modified cigar box. I replaced the top with a chalkboard material (home depot) that allows me to change the graphics (the train tracks and such) easily. It also provides a very smooth surface for the magnet driven drivetrain.
The tiny train has an even tinier magnet attached to the front engine car. Hiding just beneath the surface of the box is series of gears and a chain which also has a magnet attached to it. When the box is closed and the motor is turned on, the train will follow the path of the magnet attached to the chain.
The project contains sound trigger which is activated by the sound of a built in mechanical music box. The idea was to have the train start and stop in synch with the music box. In order to provide a more accurate timing adjustment, I also added a time out bit. In version 2 I used duct tape to isolate the speaker which helps prevent a potential feedback loop from occurring should the sound trigger hear the mp3 player. The trick was to have the music box always be a little louder, from the sound triggers perspective, than the mp3 player. A lot of trial and error adjusting the sound trigger sensitivity, the timeout bit and the synth speaker output.
In addition to the music box, there is also the MP3 player bit that provides various train sounds while the whole thing is in motion. I created the "chug-a-chug" sound by shaking a box of macaroni which worked remarkably well.
I discovered while building the project that I couldn't power both the MP3 bit and the motor without using the split wire. I found the number bit to be very useful in figuring this little problem out. Now I always keep it handy so I can check the voltage as I go for larger projects.
The Lego section
With version 2 being in a new box, I needed to create a new lego framework for the chain drive. In version 2 this was much improved. More stable and used less legos. I also used lego universal joint to connect to the DC motor axel which really helped deal with the alignment issues.
With the chalkboard top and the Lego chain design, its pretty easy to create different types of scenarios on "the stage". I'm working on a few different top designs including a couple of sailboats sailing around some islands :-)