Stepper motor "force to turn" when powered-off?

Hey everyone,
I need a stepper motor that can easily be turned when not engaged (no power applied). What is the name of this measurement, and is it specified in datasheets for stepper motors?

My application is basically a wheel that needs to be turned accurately, but that can also be turned by a person. I was looking at using a friction clutch, but they’re pretty specialised and pricey. I have some old stepper motors from some floppy drives, and they’re easily turned when not engaged. But I also have another stepper motor that is very hard to turn. The hard-to-turn stepper has an offset shaft, which leads me to believe that it’s geared so I’m fighting against the gears trying to turn it.

I hope this makes sense :slight_smile:

I believe that the term “detent torque” is used to describe the torque required to turn the motor shaft when powered or unpowered, however I doubt you will find a measurement of the latter in a datasheet.

The rest of your question is unclear. If you already have motors that can be turned easily, why not use them?

[quote=“Jim Remington”]I believe that the term “detent torque” is used to describe the torque required to turn the motor shaft when powered or unpowered, however I doubt you will find a measurement of the latter in a datasheet.

The rest of your question is unclear. If you already have motors that can be turned easily, why not use them?[/quote]

Thanks Jim. The motor I already have that would work is just in the “junk parts bin”, I need something off the shelf I can use in a design.

Typically bigger stepper motors have more detent torque, and in fancier datasheets that would be included.

For applications where you want a stepper motor to not turn under power-off, often people will use a worm-gear or threaded rod type of engagement, which is inefficient but compact in gear multiplication and inherently offers resistance.