# Small bipolar stepper 2.5 oz-in of torque

Hello

I'm new with Arduino and motors

I'm trying to figure out what I can use for my project. I need small as it is possible, fast and powerful motor with accurate degree control, not sure if bipolar stepper is what I need, maybe RC servo or smart servo...

Approximate desired size diameter 20 max 25mm on width 25mm max 30mm, which can provide a sharp turn to 180° or 360° pendulum movement from one side to another with fast switch without delay from one direction to opposite and get 3-4 back-and-forth movements in less time as it possible 1 second for example with 50-100 grams moving component

So as i understand it the torque required to accelerate a component of mass 50-100 gm from 0 to 300 rpm in, for example 0.1 seconds, 2.5 oz-in of torque should be sufficient I guess, or maybe it is a bit much, but I'm not sure which motor I can use for this case

Some advice on this direction would very be useful

Your description of the device is unclear. Please post a drawing, with dimensions, and show where the motor and the weight are located.

I agree with @jremngton. Plus tell us what the machine is for.

High torque stepper motors tend to be big and heavy and get very hot.

...R

So as i understand it the torque required to accelerate a component of mass 50-100 gm from 0 to 300 rpm in, for example 0.1 seconds, 2.5 oz-in of torque should be sufficient

That's not how you calculate torque. You have to know the moment of inertia, not the mass. That takes
into account where the mass is relative to the axle.

Torque = acceleration x moment of inertia