A slight sidetrack from Arduino stuff, but a friend asked me to write up how I did this - so here it is.
At the weekend, I helped my son build a "junkbot" - a little moving toy, built from odds and ends, and intended to look like a robot. It was inspired by this post on Hack-A-Day, plus Frankie's delight whenever I "invent" something for him.
The gist is really straightforward : stick a vibration motor on top of a base, add a coin cell for a power source, and whatever extra ornamentation you feel like. The spirit is to hack something together out of old junk you have lying around. The "robot" jiggles around due to the vibrations, and moves in random motions. It's pretty cool for such a simple little thing.
In our case, we used a bottle top for the base, because it's easy to draw on and stick things to. There's also a genre of junkbot called the "bristlebot", which uses the head of a toothbrush as the base (with the bristles as "feet") which seems to work really well too. We'll probably use one of those if we make another.
We didn't have a vibration motor to hand, although they're cheap to buy, and easy to salvage from old mobile phones. So, we improvised and superglued an off-centre blob of blu-tack to the shaft of a tiny motor that came with my Arduino starter kit.
We sellotaped a wire to each side of a coin cell to provide the power, and blu-tacked that to the bottle top. I had a simple on/off switch that I ripped out of the light-up moon project, so that was a handy way to control the power. Again, it got blu-tacked onto the base. Finally, Frankie decided that he wanted a light on his robot, so I grabbed a spare LED and wired that in.
No soldering was involved, just simple twisting together of wires, so it's not very robust. The blu-tack on the makeshift vibromotor tends to deform itself after a short while, but it's easy to just pinch it back into shape again - and the robot tends to have a slightly different character each time.