Moving a stepper motor 20 degrees in about 15ms


#1

HI there
My names Rick.
I’m looking at using a stepper motor to rotate a shaft through 20 degrees, but I want to do it very quickly, (approx. 15ms).
My question is that viable?

Cheers
Rick


Introduce yourself!
#2

That’s a good question. Do you have a particular stepper motor in mind, since every stepper has a number of physical characteristics that would let us figure this out on paper before we try powering it up.

Let’s take a NEMA 17 sized stepper, common in hobby CNC applications, as an example:

  • Step angle - 1.8degrees
  • 200 steps/rev

The best I can find for speed is in this document: http://www.ni.com/pdf/products/us/cat_steppersandencoders.pdf

It says “3000 rpm max speed”, this ( if I’m not mistaken ) equates to 18000 degrees a second, or 18 degrees every millisecond.

At this speed, however, your torque has been significantly reduced- about 0.25N-m at 36 VDC / 1 AMP- and this may be necessary for your application. So let’s reverse the calculation:

20 degrees / 15ms = 1.333333 degrees per ms - let’s round this to 1.4 degrees per millisecond

So we have 1400 degrees/second, 84000 degrees a minute and a speed of 233.333 RPM. Now we’re looking at more like 0.41N-m torque at 36 VDC / 1 AMP.

So, with the right driver it looks easily possible- but it depends on your choice of stepper!

Everything posted above may be complete nonsense, since I’m no stepper expert, but your prospects look good on paper.

There’s some good information here, but the gist is that “it’s complicated” http://forum.arduino.cc/index.php?topic=75930.0


#3

Cheap 5V BY stepper does 12rpm
so 360 degrees in 5 Secs
20 Degree in 277mS
so going to have to go upmarket a bit
Simon