Stepper Motor Failing--Electrical Interference?

The motors remained wired together as shown even when swapped and the 'far' motor still failed? When you swapped motors did you change the connections also? If so is it possible the phases on the far motor are not connected properly?

I'd also put each motor on its own dedicated driver. Wiring them together as you have can introduce electrical weirdness.

the 57BYGH001 stepper motor has six leads. You show four.

How many leads you use, depends on the type of driver used. A 6 lead motor can use either type of driver, that is 4 or six leads, but he may have a wiring error because one motor's leads, colour coded, but wrong....

4 leads = Bipolar. 6 Leads = Bipolar (center connections not required) or Unipolar all connections needed (I hope I got them the right way round!!)

The Bipolar changes the polarity of both connections to any pole coil, and the Unipolar, keeps the center connection usually on ground and applies a positive voltage to one or the other end for a change in direction.

Because only half a coil is used at any one time, the unipolar connection does not get as much torque from the motor as Bipolar does....at extreme speeds, the Bipolar can run faster and more accurately and is usually preferred by professionals....

Its easy to use an ohmmeter to identify all the leads 100%.

See here:-

https://en.wikipedia.org/wiki/Stepper_motor

Here is a Unipolar diagram, illustrating as to why it can be driven with either driver type:-

Sorry, correction, Unipolar needs 6 leads. Finger trouble!!

Yes. Some also connect the two centre leads together internally and bring it out as a 5th lead.

Good thought, reversing both coils sounds like the kind of mistake that someone might make without thinking.

You and I both know that more often than not, one picture has the weight of an entire lengthy tome.

How true!

What happens if you disconnect Y1? Does Y2 run OK then?

The problem is intermittent: is one of the connectors at Y2 a little bit loose? Try re-crimping and some contact cleaner.

Have you got an oscilloscope so that you can see what signals are actually getting to the stepper motor?

What you are doing is very interesting. I would love to dig into the data sheets and try to give great suggestions but I just don't have time now.

After several decades of electronics I still find myself and others repeating some of the same beginner mistakes. With respectful intent I ask the following beginner questions:

1. Are you confident that the wall wart supplying power to your Arduino is rated IN EXCESS of your power requirements?
2. Are all connectors properly soldered/crimped and in good condition?
3. Are you confident that it is wired the way you think it is?
4. Is the motor inrush that the stepper driver might be passing causing problems?
5. Any chance you have a "not wire" in a place where you think you have a good wire?
6. Are you sure your motors are wired up correctly?
7. Are there any polyfuses in the circuit that act properly when you are debugging but cause problems when you are operating?
8. Are you making any assumptions that are possibly not valid? Remember what "they" say about assumptions, they make an ASS out of U and Me (PTIONS).

The most likely diagnosis given the symptoms you've described is a bad connection to one of the windings on the "failing" motor.

..which cannot be seen from here.

Check the resistance between the far motor and the driver, or check for voltage drop (AC) in the wiring between the driver and motor while the driver is turning the motor. Having swapped the motors, wiring and connections are the only difference between the two motors.

Another thought: Possibly your driver is only marginally capable of driving two motors. A slight added resistance in the far circuit could make the difference.

On general principles I don't like two motors driving the same axis of motion, unless there is some designed in slip mechanism (e.g. friction clutch, fluid bypass, flexible shaft). If there isn't a planned slip then there will often be times where the two motors will be fighting each other due to some random misalignment. I also do not like the idea of driving these two motors in parallel with the same driver electronics. The available torque from each motor will be different and uncontrolled. Thus a misalignment of the axis of motion will more likely happen. However, this is just my preference. I would not be surprised to find this configuration does work in some application. Most likely the designer got lucky instead of carefully engineering around my concerns but I don't dispute that a clever engineer might succeed.

I wish you good luck.

My feeling also.

But in paragraph 6 of initial post it says taking drive belts off motors does not stop fault symptom.

I have asked for a connection list.

Is this just a plan stepper motor or is it a hybrid stepper motor (Closed loop with an encoder)

this one.

As you probably know, wiring to/from Arduino boards can be a bit tricky, and often times there

will be intermittent connections, or "no wires" where you think there is a solid wire.

Go through the wiring with resistance or continuity checks. Make sure never to apply negative

voltage on any part of Arduino.

It would help if you explained what you mean by "reversing the connections".

Give us a list e.g.

Driver , Y1 , Y2

AOUT1, RED, YELLOW

AOUT2, GREEN, BLUE

BOUT1, YELLOW, RED

BOUT2, BLUE, GREEN

As pointed out, that the motor has 6 leads and the Driver 4 needs

addressing.

The symptoms sound to me like the phases are out-of-order on the far motor. I don't know why the OP doesn't just use an idler where the far motor is. If he needs more torque, use a bigger motor. As mentioned earlier, two motors driving the same load sets the scene for all kinds of problems, even when the phases are done right.

If two connections to a step motor winding are exchanged (such as A+ and A-, or B+ and B-), the motor will behave exactly the same but with the direction of rotation reversed.

As these are steppers, they should exactly track each other (within the minimum step angle, typically 1.8º (or 0.9º in half-step mode), unlike e.g. servo motors which can lead or lag by a few degrees, leading to "crabbing", which could jam the drive system.

Here's someone who is trying to the same thing as you are (unless it is you ), i.e., driving two stepper motors at the same time.

http://forum.arduino.cc/index.php?topic=1

You just may have to bite the bullet and use another DRV8818 driver for the second y-axis motor.

I'm just wondering if the signal pulse is just too weak.

Why not put a relay into the mix? As long as it is not a solid state relay, it might work. (SSR's are notorious for not turning off when the relayed power is DC.)

Link should be:

http://forum.arduino.cc/index.php?topic=179973.0

I could be mistaken, but the 57BJGH001 is described as unipolar [4 windings, the third wire of each winding is power common centre-tap, 6 leads],

while the Driver circuit is bipolar [two windings, 4 leads].

Maybe a three-legged race by donkey and monkey, falling over sometimes.........

And H drives make really powerful pulsed power in some applications such as electrolysis, as I understand.

So the motor will work with bi-polar. I have tried several times to trace proper data sheet for motor on internet - without success.

No one has yet referenced more than connection and resistance data for the motor type - in the vague way of some data, it is not clear whether 5 volts and 5 ohms and 5 mH applies to half a winding or the whole - unipolar = driving half-winding. A whole winding might be 10 volts, 10 ohms, 20 mH.

The driver datasheet indicates there is a shutdown current limit circuit, about 2 amps max and a PWM limit which is adjustable. Two motors would be 2.4 amps or more

With two motors, and 12V supply it may be that the PWM limit is only allowing half the proper current to each motor - one is likely to malfunction, probably the one with the longest wires = Y2, it may work until it heats up and its winding resistance increases.

The original post has not told anything more than in first post, nothing about how fast he is driving motor, connections, PWM current limit.

The advice to use a driver for each motor seems the best, particularly if part stepping is being used to get better plotter resolution.

Too bad there is no category : very good answer, or excellent answer. WTG Andy!!!

As I'm sure you know, the reason why higher voltage is needed (especially at higher step rates where there are only milliseconds between switching a winding on and off) is that the inductance of the coils means it takes a while to get enough current flowing to generate the required torque.

The higher voltage means that the current can build up more quickly.

Steppers are prone to miss step and stall for a variety of reasons....accelerating too fast- and at higher speeds are harmonic sensitive,

harmonic can be mechanical ( I believe this is most likely the problem as you are using 2 motors on 1 shaft) and both motor step signals

do not happen at the same time....1 motor steps and temporarily sees the other as an additional load...you would be better off to use a

larger motor and driver, or reduce the load by pulley reduction and deal with a slower speed on that axis with the smaller motor...

I have seen dual motors used before, with apparently no problems, provided they are identical, but I have never sone it myself.... Your post is good and I believe accurate, if there are any differences between the motors.

Hi Andy, what I was thinking is the step motors cog, i.e. step, stop, step, stop, and do this at some clock freq, controlled by the 'arduino', and these clocks are not synced so both motors step at the same time, so the clocked motor sees the stationary motor as an additional load and stalls...might work to use the same clock on both drivers...if both are running in the same direction...if they're direct coupled ti opposite ends of the shaft, the timing through the driver running the motor in the opposite direction could differ and again cause a stall...

The motors are connected in parallel - to the same driver via the same bits of wire! How could they possibly not step at the same time?

If they are paralleled on the same driver you probably have harmonic ringing between the coils of 1 motor feeding back to the other motor, due to the imperfect matching of the coils...

If one is not allowed to, by being held between positions a little maybe.....because the toothed wheels are not positioned correctly.

Se my previous post.

I have negated the OT someone gave you.

You set me thinking, I wonder if the small toothed wheels mounted on the motors were wrongly set, so one of the other motor is not at a set position, maybe what you fear (assuming I understood you correctly) could be happening.

Assuming not shafts with flats on them, loosening the set screws on one and moving the toothed belt a touch then tightening them up, should do it!!

With flats on the shaft, one or both motors may need to be turned a tiny amount....smaller screws with washers might allow some small movement!!

I hope I made myself clear.....

Afterthought: alter your software so the motors sequence is switched in software and you'll probably find the other one drops out...

Switch to an L/R driver and I'd bet the problem goes away...