For the past several years, I have been building a 78 RPM record player. I have decided to drive the main platter with a separate small spindle (connected via a belt to the main platter); and for speed precision I've decided to use a stepper motor to drive the spindle.
The spindle's diameter is 1 inch, and the platter diameter is 10 inches; so the 10:1 reduction means that I need my stepper motor to spin at 780 RPM.
I've seen videos of people driving stepper motors at such high speeds, but until now I've only been able to drive my (unipolar) stepper motor at very slow speeds (e.g. 40 RPM). Anything faster than that and it stalls out.
My question is:
What type of stepper motor (Bipolar or Unipolar) will I need to be able to achieve 780 RPM using the Arduino Motor Shield, and what code should I use to run it?
Don't use a stepper motor, they vibrate right in the audio band, and you'll probably pick up direct
magnetic interference all across the high frequencies as well from the chopper-driver.
You need a smooth running motor, preferrably synchronous AC (that's normally what's used).
I'm a little new to the terminology, though- what is it that you mean by this?
MarkT:
they vibrate right in the audio band
Also, this may be surprising, but I'm actually using an entirely mechanical/acoustic sound reproduction system (think old-timey gramophone) so I don't think this will be a problem:
MarkT:
you'll probably pick up direct
magnetic interference all across the high frequencies as well from the chopper-driver.
Stepper motors physically vibrate on every step. You can reduce this by using microsteps, but
you don't want a source of acoustic vibration on a turntable, other than the groove in the disk!
Doesn't matter how you amplify the vibrations, you will pick them up I fear.
