I am trying to drive a mini music box with a toy DC motor and my arduino. The music box has exposed gears with teeth on them. My motor shaft doesn't have any gears on it. How do I hook these two together? I get that I need to buy some plastic gears to fit onto the motor's shaft, but is there some tricks to getting the motor and the music box gears lined up properly?
Small motors like that usually spin very fast: on the order of thousands of RPM. You'll want to crank the handle at a speed on the order of dozens of RPM.
Rather than try to find matching gears, I suggest looking for a geared-down motor (like the ones sold by Solarbotics, Pololu, or model vehicle shops). One of those servos modified for continuous rotation might do nicely.
You could connect to the crank using something like a servo horn, or a wheel with a hole drilled at the right offset.
Then you mount the box and motor to a piece of wood or plastic to hold them in alignment.
Thanks for the ideas. I will get a gear-motor. I just finished hacking a servo to behave like a motor and it does the right thing, but it's too loud and will distract from the sound of the music box (which may eventually be recorded, so quiet operation is key).