Identify stepper motor

How do I identify what kind of stepper motor I have on my rotary currently? I’m ordering a different kind but I have to supply the motor and it calls for a NEMA 17.

If you are looking for an exact match, there is usually a sticker on the existing one that will help you cross-reference the specifications and get “at least as good as.”

If that’s not available, or you can’t find the reference, check the physical length, shaft length, shaft diameter, and start there. NEMA-17 gives the dimensions of the mounting holes, so you don’t need to worry about that. For a rotary you probably don’t need to worry too much if the stepper is bigger, but the shaft size will need to match unless you want to modify things. Also for the rotary, you probably want at least 1 amp but no reason to go beyond 2 amps.

Steppers are commonly available in 0.9 degree (400 steps per revolution) and 1.8 degree (200 steps per revolution) step angle. That doesn’t really matter but if you don’t match the step size you’ll need to multiply or divide the steps per revolution count.

Also, make sure you check the wiring; usually 3, 4, 6 or 8 wires. If you have an exact match you should be safe. You can play wiring tricks for some other combinations, but you start adding variables to the equations.

Thanks, for the information.