Prof Wonmug wrote:
I want to make some "spinners" with my granddaughter. These are disks
with various patterns that do interesting things when spinning. Some
change colors: yellow and blue wedges turn green, all colors turn
white. Some appear to spin backwards. Some are spirals. Benham disks
generate colors from black and white:

http://en.wikipedia.org/wiki/Benham's_top

These can be made with toothpicks like a top, but the best effects are
achieved with more controlled spin speeds. Most of them work best at
fairly low speeds (150-300 rpm).

I have an old Makita cordless drill, which works OK, but the speed is
difficult to control precisely and it's way overkill. I also have a
Dremel tool, but its slowest speed is like 2000 rpm, which is way too
fast.

Does anyone know of a simple tool, like a cordless screwdriver, that
has better speed control and goes down to 150 RPM?

Or does anyone have a better suggestion?

Is there some kind of simple turntable?

I need speeds of 150 to 1,000 rpm (I think).

How much trouble would it be to build a simple hand-cranked turntable
either gear or belt driven?

How about using old 12 volt DC fans out of computers. With a variable resister
fed from a 5 volt power supply to power them, you might be able to get the
speeds you want.