Steppers in series

Thread Starter

PathogenIX

Joined Oct 14, 2020
21
Hi all
I have a 24v stepper output pin header

I want to replace the single 24v stepper with x2 12v steppers
12v Motor specs are =
Voltage = 12v
Current = 0.4A
Resistance per phase = 30Ω±10%
Inductance per Phase = 37mH±20%

So steppers in series would need?
Voltage = 24v
Current = 0.4A
Resistance per Phase = 60Ω±10%
Inductance per Phase =74mH±20%

Will i need to compensate for any inductive kickback? Will the increase resistance+inductance cause any issues with the driver?
 

shortbus

Joined Sep 30, 2009
8,797
I wouldn't do it. Voltage as shown on a stepper motor name plate or data sheet means little or nothing. It's the current that makes the difference in stepper motors. Steppers are normally run at many times their voltage rating, to make them step with more authority/force so they don't loose their "place"(miss step).

Also when you say you want to put two of these motors in series, do you mean couple the shafts together? To get more power? That type of thing is risky also. There is a large chance that the rotors of the motors aren't aligned magnetically and could/would fight each other.
 

Thread Starter

PathogenIX

Joined Oct 14, 2020
21
I wouldn't do it. Voltage as shown on a stepper motor name plate or data sheet means little or nothing. It's the current that makes the difference in stepper motors. Steppers are normally run at many times their voltage rating, to make them step with more authority/force so they don't loose their "place"(miss step).

Also when you say you want to put two of these motors in series, do you mean couple the shafts together? To get more power? That type of thing is risky also. There is a large chance that the rotors of the motors aren't aligned magnetically and could/would fight each other.
Thanks everyone for the speedy replies!

I'm speaking of a series electrical connection. Each phase wired in series.

Phase 1 = PWR->Motor1Phase1->Motor2Phase1->GND
Phase 2 = PWR->Motor1Phase2->Motor2Phase2->GND

Are there any tests to check the viability of this?
I have found many Ysplit stepper control cables online which is what gave me the idea to begin with. (See Picture 7)
I found this Instructable but it doesn't explain much about the principle behind it...

Can anyone tell me why this would be a bad/uneducated idea? Surely so long as i have enough voltage and current to feed the steppers what they need, i shouldn't have a problem right? Both 12v steppers are from the same manufacturing run so diffences in coil impedence and resistance should be negligable?

More reference links
- Stack Exchange Post
-V1
-Regret
-Utube
-V1
 
Last edited:

crutschow

Joined Mar 14, 2008
27,696
For one thing, if one of the motors is mechanically stalled, the other sees nearly 24 V.
That's true for a standard DC motor, but not so much for a stepper.
Its current draw is only moderately affected by the load.

I think you could likely put the windings in series although it may depend upon how much of a load each motor is driving.
Are they driving the same or different loads?
 

Thread Starter

PathogenIX

Joined Oct 14, 2020
21
That's true for a standard DC motor, but not so much for a stepper.
Its current draw is only moderately affected by the load.

I think you could likely put the windings in series although it may depend upon how much of a load each motor is driving.
Are they driving the same or different loads?
Ideally they will be driving the same load.
 

cmartinez

Joined Jan 17, 2007
7,393
Normally, Stepper Drivers regulate the amount of current going through a motor. I'm assuming that you want to connect them in series so as to use only one driver, right? Well, it would probably be a better idea to connect them in parallel and set the driver to double the amount of current going through them. Otherwise the driver would double the amount of voltage to drive the current set for a single motor, and that would probably seriously affect its components.

Keep also in mind that steppers are prone to electric "ringing" when switching their coils, and said ringing could damage the driver if it increases drastically or resonates due to the series or parallel connection.

Personally, I think it would be much wiser, and easier, to simply use one driver for each motor.
 

shortbus

Joined Sep 30, 2009
8,797
Ideally they will be driving the same load.
So then you are using them together for one load. The links you gave were looking at a different problem, the *jerking* of the axis when micro stepping. If that isn't what your trying to cure trying to synchronize two motors is going to be harder than you think. Your better of just getting a bigger stepper motor, they make different sizes. The sizes go by a NEMA identifying number the larger the number the more power.

If your using the motor driver the people in the links show, DVR8825, The Polou web site states, " This stepper motor driver lets you control one bipolar stepper motor " So I wouldn't drive two. https://www.pololu.com/product/2133
 
Last edited:

BobTPH

Joined Jun 5, 2013
3,652
That's true for a standard DC motor, but not so much for a stepper.
Its current draw is only moderately affected by the load.
For distinct steps, I can see how that would be the case, but if the motor is running continuously wouldn't it produce back-EMF similar to a brushed or other type of motor?

Bob
 

MaxHeadRoom

Joined Jul 18, 2013
23,595
A stepper motor should be ran at a constant motor plate current, no higher-no lower.
Modern drives are generally supplied with a much higher voltage that the plate rating, but use current monitor techniques to ensure the correct constant current as inductive reactance increases,
Max.
 
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