# Stepper Motor Anatomy and Logic

MachX
Hello all,

I've been learning and trying to reverse-engineer the logic, nature and anatomy of a stepper motor. In my quest I am trying to figure out what any given stepper motor will draw at any given rpm with given specs about the motor.

These motors come with certain specs as far as Vmax, A/phase and so forth. I have learned that a 1.8degree motor is 360/1.8 = 200 steps in the motor.

when trying to calculate desired RPM you use PPS (Pulse Per Second). in this case if we choose a desired 500RPM for the motor to output... the math would show:

(500Rpm / 60sec-min) = 8.33Rps.
Then
(200steps-in-motor-per-rev X (8.33Rps)) = 1,666 PPS.
Then
If I calculate (1rpm/60sec-min) = 0.016667 -> (200steps X (0.016667)) = 3.3333PPS
Would I assume that a 1.8 degree motor is always 3.33PPS per step?

My question is: If I want 500Rpm out of this motor....and I need 1,666 pulses per second to achieve 500Rpm, how is PPS a function of Voltage, Amperage and resistance? What would be the draw of the motor in and V and A at 500Rpm and 1,666PPS? And/or how would I calculate this if I have the ratings for the motor? Any advice appreciated.

Gold Member
2021 Award
Hi MachX

not to sure what you are trying to achieve
I suspect you misunderstand the real use of a stepper motor :)

Steppermotors are rarely used that way, thats why we have normal motors
Steppers are primarily used for low speed and hi torque precision stepping forward and back eg. in a printer/scanner/photocopier ... the 2 axis drives for a telescope, a hard disk drive head positioning

cheers
Dave

MachX
Hi Dave, I am trying to experiment with something similar to this:

http://youtu.be/pHYSqkuTIno

The stepper is good for this type of project due to it being low rpm. If I wire each phase output through a voltage doubler circuit I might be able to get the 5v 1A I need for USB devices after rectification drops.

I was just trying to understand how I could possibly calculate input rpm to reach a given voltage, this way I would know what gears or pulleys I need. cheers