Stepper clarification

Just a quick question to confirm what I think:

Controlling a stepper motor is basically a case of saying “move n steps in this direction”.
Controlling a servo is more a case of simply saying “move to this angle”.

So I guess a stepper would probably want some sort of feedback mechanism so we know where it is, and if it still needs more steps.

Providing your stepper motor is working within its specified torque range then feeding it with "X" step pulses should make it rotate by "X" incremental degrees. However, you need to be able to establish where it is when you power up. There are a couple of simple ways, and the simplest of all is to drive the stepper until it triggers a switch of some sort, be it mechanical or optical. This establishes a reference point from which you can then move the stepper to all other "known" positions. Your software can periodically re-establish this reference to give confidence. With a feedback pot you "know" where the stepper is at all times but the resolution of such a system can be no better than one incremental movement so even a feedback pot does not give an exact position, and you may induce hunting as the stepper motor endeavours to establish an exact position.

Servos on the other-hand have a built in feedback control but their power and resolution are feeble compared to the power and capability of a stepper.

jackrae:
their power and resolution are feeble compared to the power and capability of a stepper.

Sounds ominous!

Thanks for the info though :smiley: