Step motor step degrees amount?

Hello, I'm just brainstorming at the moment. How can you tell how many degrees a step motor steps? I was thinking about attaching a step motor to an Earth globe, and wanted to step to certain points. I'm sure I could just hook it all up and figure it out on the fly by counting number of steps in 360 degree turns, but am curious now just the same. Do different step motors step differently, or is there a standard step?

Thanks for tolerating lack of knowledge in this area. I look forward to feedback :)

It will depend on the construction of the motor, and will be a listed spec. If you can't find the manufacturer's specs for a particular motor (scavenged or surplus, for instance), I think you're stuck with counting steps.

Also while a given stepper motor may have so many physical poles that determines it's number of steps per revolution there are ways of using driver electronics and controls that can micro-step a given stepper motor for finer steps.

Lefty

Steppers commonly come in 72 and 200 steps per revolution. Turn the shaft by hand and you should feel the steps. Count out about 20 of them. If you've made about a quarter turn, it's most likely a 72 step model. If it's closer to an 8th turn (a 10th, to be precise), it's probably a 200 step model.

If you are micro-stepping it is not usually a good idea to try to hold at positions other than a full or half step. Holding torque is dramatically reduced between those points and the motor is likely to slip over to a full or half-step position. This can result in dropped steps and a need to re-home the axis (get the actual position back in sync with where the controller thinks it is).

Microstepping is really a technique for avoiding mechanical resonance which causes step loss or stalling, not for increasing step resolution. Half-stepping does increase resolution at the cost of holding torque. If you need higher resolution you should use a reduction drive (gearing or belting).

And, BTW, don't disassemble steppers if you can help it. I've read that the rotors are sometimes magnetized after assembly and removing them can result in a substantial loss of magnetic strength and therefore stepper torque.

Hey all, Thanks for the fantastic feedback. That gives me all the info I need to doodle with. I feel smarter now. Now... to put it to use. I can't wait! :)