I have a little hand-cranked music box like this. I’m thinking about adding a small motor and drive circuit and making a nice box for it with my laser cutter. This Youtube video shows one example of exactly what I’m trying to do, but he uses a small geared DC motor which sounds very loud. Is there a better choice of motor? I also have access to 3D printers and basic electronics parts & equipment, and have some Arduino experience. This is mainly a hobby project and learning experience, so I’m happy to do it the “hard way” if it improves the outcome.
Also, is there a better way to detect the end of the song (i.e. better way to count the number of turns)? Use a stepper motor instead of a DC motor? Microswitch? Optical encoder?
Stepper motors are quieter than gear motors. Is the song just one rotation of the drum? Seems easy to count the steps with a stepper motor to stop at the end. You may not be able to drive the drum directly without detaching the worm drive, but if you did that you’d reduce the number of steps and any possible noise… Depending on the motor you still might need some reduction for a direct drive to keep the motion smooth.
Thanks, I haven’t worked with small stepper motors and wasn’t sure about noise. I know servo motors (like on RC models) can generate audible whining noise.
The song is one rotation of the drum. Maybe I could cut off the handle and connect the worm gear directly to a tiny stepper motor. The song would then be an integer number of rotations.
Stepper motors vary in the level of noise they produce just like any motor. But gear motor noise comes from all that gearing which is often under lubricated (or I should say has just enough lubrication for operation but with no effort to reduce the noise. I have repacked gear reductions with heavy grease to cut a lot of noise out. Stepper motor noise is much lower, just a series of thuds at low speed, and that is much easier to insulate.
See if you can attach some kind of pulley or timing wheel to the crank handle instead of cutting it off. It’s hard to make out how that worm gear terminates but maybe you could extend it out the back end somehow, or extend the shaft of the gear that the worm is turning.
you’d probably want to use a motor with a worm gear reduction drive; they’re going to be a lot quieter than regular straight cut gears. Check with places like hobbyist and amateur robotics products. or something like this: https://www.amazon.com/Small-Worm-Reduction-Geared-Motor/dp/B00NLZGDHA
they’re not going to be completely silent, mind, most of the time they used brushed DC motors and there’ll always be some noise from the brush-commutator interface.
I think you might prefer a small open frame shaded pole induction motor. They are about as quiet as can be, and if you are loading them with a small fraction of their rated torque, their speed is quite steady.
I’d go with a small stepper motor and a belt drive, you can print a pulley to fit the worm gear shaft. The good thing abou a pulley is that you can keep any unwanted vibration from the motor to the music box mechanism.
Even if you don’t use a stepper a belt drive would let you play with the reduction ratios to match whatever type of motor you chose.