I want to use a Stepper motor to rotate a potentiometer. the potentiometer rotates at about 270 degrees. Is there any way that I can stop the step motor not to pass those positions? I don't want to accidentally break the potentiometer.
Yes. You can use the potentiometer output as a feedback to the Arduino using an analog pin. This will tell the Arduino the exact position of the potentiometer, so the code can ensure it does not move the stepper motor too far in either direction.
Your program controls each step that the stepping motor takes, so you should always know the shaft step position, relative to the starting position.
However, you need some mechanism to know the starting position, and which step positions correspond to the potentiometer limits.
Options include a mechanical "home" stop, shaft encoders and limit switches. It does not damage a stepper motor to stop it mechanically, so a shaft collar can be used to limit the range of motion.
thanks. the potentiometer is used as a volume for a speaker. Can I still use it this way when it is in a circuit?If yes can you help me with the code.
I think the most robust way is to engineer a mechanical stop at each end of the required travel. When you start up the system you drive the stepper all the way to the low volume end by sending it enough pulses to traverse all the way from maximum volume, should that be necessary, plus a few more for safety. When it reaches the lower end of the travel it will just rattle against the stop until the pulses finish.
At that point you know the potentiometer is at the low volume end of the travel, so you can then initialise a "position" variable which you update when you move the potentiometer. Theoretically you don't need the mechanical stop at the maximum volume end, because your software always knows where the potentiometer is, but it is better to fit one in case your software has bugs.
If you prefer to use limit switches, the initialisation procedure is essentially the same. Mechanical protection of the potentiometer is the least likely to go wrong, though.
No. You could do it with a ganged or stereo pot. This is where one shaft controls two pots, one will be in your audio circuit and the other feeding into the A/D of the Arduino.
Why give such advice? Especially for a music lover.
Because I've seen it done this way before. Of course, that initialisation sequence isn't used while the person is listening to music, but only at switch-on.
Personally I wouldn't use a stepper motor for this application - motorised pots are easy to buy and much better because they are silent, and have an integrated slipping clutch for protection.