# variable speed stepper

#### shuki

Joined Apr 5, 2020
1
Hey there,

I am trying to figure out a simple way to control the speed of a Nema 17 stepper motor with a potentiometer. I would like to figure out a way to do this without any programming, I know how one would do this with a DC motor but I'm not sure if that translates to a stepper. Does anyone have any thoughts on how to do this?

Thanks, Shuki.

#### OBW0549

Joined Mar 2, 2015
3,566
I am trying to figure out a simple way to control the speed of a Nema 17 stepper motor with a potentiometer. I would like to figure out a way to do this without any programming, I know how one would do this with a DC motor but I'm not sure if that translates to a stepper.
It does not. You control the speed of a stepper by varying the frequency of the steps, not by varying the motor current.

Does anyone have any thoughts on how to do this?
This is not a simple subject. The attached will provide some details.

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#### Papabravo

Joined Feb 24, 2006
15,810
Put the stepping sequence in an 8-bit shift register, and control the clock with a VCO.

Joined Jan 15, 2015
5,916
NEMA 17 really only tells us the dimensions of the motor face. You need to know the current and voltage for your motor before you worry about driving it. With that known then start looking to stepper motor drive circuits and if your motor is for example 1.8 degree steps and can use half step you consider that. You can buy an off the boat driver and as mentioned just use a simple VCO. Inexpensive and simple. That assumes a hobby application.

Ron

Joined Jul 18, 2013
22,887
Also is it a bi-polar or uni-polar stepper?
As Ron said, NEMA17 is just mounting data.
Max.

#### MrChips

Joined Oct 2, 2009
23,286
A stepping motor is called a stepping motor because the motor in driven in steps.
If you give the motor n-steps per second it will step n-steps in one second.
If you give the motor n/2 steps per second the motor will rotate at half the speed.

#### jpanhalt

Joined Jan 18, 2008
11,088
It is impossible to control the speed of stepper motor just by using the potentiometer. Its speed can be controlled by varying its frequency steps.
Ah, but you can control frequency with a potentiometer. Done it dozens of times with an NE555. I see no reason that a stepper control can't be so controlled. Now, whether I would want to waste time designing a circuit to do it without any programming is another question. I highly suspect such controls are available on Aliexpress, eBay, etc.

Joined Jul 18, 2013
22,887
It is impossible to control the speed of stepper motor just by using the potentiometer. Its speed can be controlled by varying its frequency steps. While for controlling other DC motors, we can use potentiometer to vary their speed by limiting current but
But it is no different for each style of motor, IOW they both usually require a controller of some kind.
You do not usually control a DC motor with a pot, directly.
Max.

#### AlbertHall

Joined Jun 4, 2014
11,239
You do not usually control a DC motor with a pot, directly.
Except Scalextric and model trains (before they went digital).

Joined Jul 18, 2013
22,887
Except Scalextric and model trains (before they went digital).
I was talking in the present context!
Max,.

#### Ian Rogers

Joined Dec 12, 2012
871
Put the stepping sequence in an 8-bit shift register, and control the clock with a VCO.
Exactly what I was thinking... Forwards and backwards!! I was thinking four bit shift register fed by a timer..

#### Papabravo

Joined Feb 24, 2006
15,810
Exactly what I was thinking... Forwards and backwards!! I was thinking four bit shift register fed by a timer..
I think it needs to be eight with the phases connected in the order required for the preload constant of 0xE0 to produce the half step sequence.
If the register can shift in either direction then from any state the process can be reversed.