programmable top

This is a top with a row of LEDs on a radius, that flash when it spins, creating a circular image using the persistence of vision effect. You can draw an image on a circular piece of paper, and slowly rotate the top over it to scan it in, so that it will display when you spin it.

One problem is how to sync the image. POV displays on wheels usually sense a magnet in a fixed location, but the whole top will spin. Perhaps an accelerometer could tell accurately enough how fast it is spinning to be able to sync it? Maybe the top needs to have a fixed base?

Another problem is how to scan the image. One idea would be to do resistance sensing of graphite lines. The sensor would be a row of metal brushes that would press against a pencil drawing. They could detect a drop in resistance where you had drawn compared to where you had not. So that leaves determining the rotational position of the scanner while you are scanning... another reason to have a fixed base for the top.