stepper motor weight handling and torque

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ndnbolla
 
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Joined: Tue Mar 31, 2015 11:17 am

stepper motor weight handling and torque

Post by ndnbolla »

Hello,

I am confused at how to calculate the amount of weight a stepper motor could potentially rotate.

I am designing an adjustable screen mount that will be able to tilt and rotate. For the rotating part, I think using a stepper motor would be the best bet.

Lets say I have a rectangular case about 1 kg in weight (holding a 7" TFT screen, Arduino Due, and a shield in between enclosed in wooden case.. The stepper motor will be attached to the rear center point of this cuboid using a mounting hub and will be able to rotate the screen/case either 45 degrees counterclockwise or clockwise.

Now my question is, would this stepper motor work: https://www.adafruit.com/product/324

At "28 oz*in, 20 N*cm, 2 Kg*cm holding torque per phase" it seems like it would ave enough torque to be able to rotate and hold.

Also do stepper motors require a constant source of power in order to hold something like this in place?

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adafruit_support_bill
 
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Re: stepper motor weight handling and torque

Post by adafruit_support_bill »

"28 oz*in, 20 N*cm, 2 Kg*cm holding torque per phase"
That means it can resist a force of 2Kg at a distance of 1 cm from the center of the shaft. If your ~1 Kg assembly is reasonably well balanced, it should be able to hold that position.

Acceleration is a bit more complex. You would need enough torque to overcome the moment of inertia for the load. http://en.wikipedia.org/wiki/Moment_of_inertia
The torque of a stepper motor decreases with speed, so the torque available to overcome the inertia is going to be less than the holding torque. These pages give some more detail on the topic and some handy equations.

http://www.orientalmotor.com/technology ... tions.html
https://www.pololu.com/blog/10/force-and-torque

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