I wanted to know what type of component or module I could use to make a hollow ball move. I have these hollow plastic balls (think empty easter eggs) that I was going to put a nano in and a sound detector and was just hoping to just get it to move. I prefer a sort of a tilt left and right effect, but if it just rolls randomly that would work as well.

I was thinking just a simple vibration, but it doesn't really shift the ball at all, so I'm at a loss without building something quite complex with magnets or something. Perhaps a motor stuck to the side?

  • A motor with an asymmetric weight will do it. Or, you could be more sophisticated: look at the Sphero BB-8 teardown. – uint128_t Mar 6 '16 at 5:14
  • That sounds like a good idea. I assume you mean attaching the motor to the side, and the asymmetric weight will cause it to rock back and forth. I will try that, though the motor I ordered off Aliexpress will probably take a month to get here. :P – user3787031 Mar 8 '16 at 5:21
  • The motor (and weight) could be inside the ball. If you slowly increase the speed of the motor. The ball should begin to roll, since the center off mass would be displaced (I believe). You could indeed just fully power the motor, making your ball shake and rock (and be totally out of control). – Paul Mar 17 '16 at 10:16

The ball moves are made by a simple physics principle called Conservation of Angular Momentum. The angular momentum is a property that has any object that rotates and is proportional to its mass and velocity. To make a ball move you should play with this momentum, using its simplest application, the mechanical gyroscope. The mechanical gyro is made of a heavy disc rotating at high speed, modulating its velocity you can change the momentum and create a force that will move your sphere.


Maybe some sort of bristlebot? Try a hexbug nano and see if it behaves acceptably. The key behind them is a vibrating motor on top of a biased bristle that turns the vibration into a biased motion.

  • 1
    These sound interesting. Do you have any recommended/preferred sites/pages that you could link to in your answer? – Greenonline Mar 6 '16 at 21:39

Read up on Muscle Wire! I'm sure this will be the easiest most elegant solution. Basically apply a small voltage to a section of this wire in response to sound detection and it will deform, changing the centre of gravity of the ball at rest, making it move. Use two pieces and you will manage to get it to move or tilt in two directions!


Want to make a ball move? Maybe look at how sphero does it by looking at a tear down video. You have to use motors. The motor end has to be connected to a wheel which turns the outer shell. The centre which is not at all connected to the shell should be heavier than the shell.

Not the answer you're looking for? Browse other questions tagged or ask your own question.