This robot uses a solar engine circuit. A small solar cell by itself generally doesn't have the power to make a motor move, so you have to store this power up in a capacitor, which is a small battery-like storage device. When the circuit sees that there is enough power stored, it releases it in a burst to the motor, getting useful work.
With this project, our solar engine will be powering a small car in a large plastic sphere!
This technology of using minimal electronics and simple mechanical design is call BEAM robotics.
The Miniball itself was originally invented by Richard Weait of North York, Toronto.The Miniball is a amazing robot - it uses a simple circuit and the robot itself proves to be very capable, rarely getting stuck. The Miniball is mechanically complex and electronically simple. (But don't worry - the mechanical part is still pretty easy)
In this case, we aren't going to build the original Miniball, but a smaller, more basic wannabe version. This robot is extremely simple and can take a beginner less than 2 hours to build.
The original Miniball has a geared motor that moved as a counter weight around a fixed shaft inside the plastic ball container. As the motor tries to move the weight forward, the ball starts to roll in that direction.
In our case we have a motor with wheel, which spins the ball forward as it runs.
Imagine this like a hamster in a ball - it's almost the exact same thing! But in this case, we're feeding our hamster with photons!