I want to use dual motors for the axes X and Y, i.e., two stepper motors (Nema 17 1.5A) for each. I will be using DRV8825 for these axes. I will combine two steppers in a parallel way and connect to the DRV8825 for X axis, and the samme will be applied for Y axis. At this point, how should I adjust the vref value on the DRV8825?
Your help is highly appreciated, thank you.
You cannot connect two stepper motors in parallel to one current driver like the DRV8825. If the voltage of the power supply is high enough and both motors have the same characteristics, you can connect them in series. This assures that the current is the same in both motor coils.
MicroBahner, thank you very much for this information.
So, I understand that I have to connect them as shown below.
| DRV8825 | Motor 1 | Motor 2 | DRV8825 | |||
|---|---|---|---|---|---|---|
| 1A | → | 1A↔1B | → | 1A↔1B | → | 1B |
| 2A | → | 2A↔2B | → | 2A↔2B | → | 2B |
Is it correct?
Yes. Are the motors mechanically connected so that they never can come out of sync?
Not yet, but I will connect them to the same belt, which I believe will never go out of sync.
Might you have a problem if the rotors are connected with a small angular offset? One step is 1.8 degrees, and you might be using say 8x microstepping, giving an effective step of 0.225 degrees. I think that implies that the rotors need to be aligned to rather better than that. I'm sure it can be done but something to consider in your assembly?
They will be located at the two ends of a steel rod, i.e., they will be 180 degrees apart, which is an integer multiple of 1.8. Hence, I believe I will not be having any problems. Thank you for the point jhaine.
That wasn't quite my point. You need to make sure that the two motors are coupled with no small angular offset between their teeth. If you turn an unpowered motor by hand you can feel it "cogging" - both motors need to be at the same point in the cogging cycle. Should not be hard to do.
I am thinking to do it this way, first I will pulse them one by one in such a way that they have appropriate coupled positions and then I will mount them on my CNC.
Regarding the post by MicroBahner, I have made my connections with dupont wires and shells (see also here).
Just to share my solution with you, I am positing these pictures.
I have a 4 pin wire and at one of its ends I have replaced the 4 pin connector with 4x2 pin connector and made suitable jumper connections.
I made the connection due to my need, i.e., Motor A rotates CW while Motor B rotates CCW.
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