X2 Stepper Motor Selection

[dleroi]

Does anyone know of a tutorial on how to select the right stepper motor for an X2 conversion?

I don't mean just the torque requirements. Rather things like resistance, inductance, number of wires, and unipolar vs bipolar. I'm seeing listings with a great deal of variance in those parameters for motors in the same torque range.

I'll be grateful for any guidance you may provide!

- Don

[project5k]

well there is a good article on the geckodrive website that can tell you lots about unipolar and bipolar and the wiring styles for each, ie # of wires and things like that.. it also explains some stuff about powersupplies and whatnot.. i personally believe bipolar has an advantage over unipolar just in that its just 4 wires and not more, and bipolar makes more torque than unipolar.. the drawback, more complicated, and thus more expensive driver electronics..

the resistance and inductance are directly related to the wire(coils) inside the motor.. a higher resistance would tell me that you need a higher voltage on your powersupply to get the performance that you want vs one with a lower resistance... the inductance is going to play a role in how fast you can usefully spin the motor, the higher the inductance, then the slower the magnetic fields on the coils will build up and decay, and this will greatly effect the torque curve of the motor vs its speed..

i havent tested this personally, but my thinking would lead me to believe that a motor with lower resistance and lower inductance would yeild a better torque output curve vs speed rather than one with higher values... ofcourse in the same thought i also think that a higher inductance would leade me to believe that the coils have more turns, and thus a denser magnetic field...

the resistance would leade me to believe that a higher value would mean that the windings are longer(more linear feet of wire) or that the wire is smaller diameter...

just my rambling thoughts, dosent mean that any of my theories are even close to right.. but it might be food for thought....

[Robin Hewitt]

Originally Posted by project5k lower resistance and lower inductance would yeild a better torque output curve vs speed rather than one with higher values...

That's the important bit, you want to see a graph of torque against speed where the torque doesn't fall away dramatically before you reach the required speed. Next to the graph will be the volts and amps required to achieve it. If the motor supplier won't give you the graph go somewhere else because without it you are shopping in the dark.

There will be a speed beyond which you can't hammer it in to reverse without losing steps. More oz-in will elevate this speed but probably the motor torque speed curve won't be so good. If your software allows accelerations you are home and dry.

[dleroi]

Thanks, guys.

I think I understand enough, now, to make the right choice.

- Don