Wiggly motor

I've had this RepRap sitting on my workbench for the last... 14 months or so, and have finally gotten tired of using it as a filing cabinet, and would like to get the wiring working.

I'm using RAMPS 1.4, and get the behavior you see in the video here -- reprinted from the video, I'm running RAMPS 1.4, have pololu stepper drivers, and have the whole thing sitting on an Arduino MEGA 2560. I've changed out most of the components one way or another, which leads me to believe I may have a problem in how I build the RAMPS board. However, I am at a complete loss of what to test, or how to go about fixing it short of 'buy a board, don't try to solder it yourself you nooblet'.

Of note, at the suggestion of someone in the IRC room, I have found that I do not appear to be getting anything on the vref test point on any of my stepper drivers. I don't know if this is a problem with my test methodology (USB power only, D1 diode in place, connected a ground hole on the RAMPS board to the vref testing hole on the stepper driver), or if that points out a potential spot to check for trouble.

Edited 1 time(s). Last edit at 02/08/2013 08:46PM by Bahustard.

What voltage power supply do you have attached?

It's connected to a 300W CPU power supply. It's giving the standard 12V to both rails.

mine have done that when i have had my wires crossed, and when i had them stepping too fast in the firmware.

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[mike-mack.blogspot.com]

dissidence Wrote:
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> mine have done that when i have had my wires
> crossed, and when i had them stepping too fast in
> the firmware.

Wires have been tested and rebuilt just in case, even wired backwards just to see what happens. They do not appear to have any crosses that I can find. The stepping is being done by the test script on the wiki at [reprap.org] -- it's also the same behavior I saw in the actual firmware when it was uploaded. Is there something I should change in the test script and try again that way?

Have you tested a different motor on a different driver?

Motor has been swapped out. Cable has been swapped out. PSU has been swapped out. Stepper driver has been swapped out.

It looks to me like crossed wires too, and my theory is one of the coil pairs is crossed.

What I mean is, you "should" have the wires hooked up 1-2-3-4.

If you swap the pairs, and go 3-4-1-2 this is not a problem, the motor just spins the opposite direction of what it would given 1-2-3-4. Swapping the pairs won't make a difference with this problem.

What I think is happening is you have 2-1-3-4 or 1-2-4-3 as your hookup. Try taking one of edge wires out and swapping it with its neighbour, and see if that helps.

You mention you already tried swapping motors - did you wire the motors yourself or did they come pre-wired?

Remember when disconnecting the motor from the driver the power must always be off, lest you fry the driver!

I had to do the wiring myself, though I can get you the reference PDF I am using for the motor, plus the guide I was given. I am pretty certain that the actual wiring was done properly.

I did try swapping wires 1 and 2, noticed no change, plugged it in backwards, and noticed no change again. Well, it didn't magically start obeying the proper rotational laws, anyway. Still very jumpy, though at some settings it seemed to jerk wildly, instead of wobbling back and forth. Enough that it nearly sent the motor flying off the stand.

And yes, I have enough sense to kill all power before unplugging anything. PSU off, green plug unplugged, wait for the LEDs to go out.

I just had the exact same problem.

In my case it ended up being a misunderstanding about the wiring. I had the numbers and the letters mixed up. The numbers are the specific coils, the letters are different terminals, I had the opposite.


I had a classic case of RTFD, the faq located here I found helpful:

Pololu Faq for Stepper Driver

In another forum I also came across someone who had some cold solder joints on the stepper driver causing issues. That could be another thing to check, otherwise I'm out of ideas

u mean u soldered the stepper internal wires?

Bahustard Wrote:
-------------------------------------------------------
> I had to do the wiring myself, though I can get
> you the reference PDF I am using for the motor,
> plus the guide I was given. I am pretty certain
> that the actual wiring was done properly.
>
> I did try swapping wires 1 and 2, noticed no
> change, plugged it in backwards, and noticed no
> change again. Well, it didn't magically start
> obeying the proper rotational laws, anyway. Still
> very jumpy, though at some settings it seemed to
> jerk wildly, instead of wobbling back and forth.
> Enough that it nearly sent the motor flying off
> the stand.
>
> And yes, I have enough sense to kill all power
> before unplugging anything. PSU off, green plug
> unplugged, wait for the LEDs to go out.

Updating this with my current attempts.

-On the possibility of a cold joint, I went through and double-checked a large number of possible problem points (places where the solder was beaded, instead of that little mountain you normally see to show a 'proper' solder). No change.
-I did triple-check the wiring on the motor, and it appears to be fine. Unless the... actually, you know what? Here's the motor specs. [dl.dropbox.com] -- I tried A1 = A and A1 = A-with-a-line already. I don't think that the "A COM" has anything to do with what I'm doing here.
-I got fed up enough with myself and admitted I probably screwed up the board, buying a new set of RAMPS and steppers from RepRapDiscount. It, uh. It does the exact same thing.

My current theory is a potential problem with the actual Arduino, but I'm having trouble testing that.
I don't know what you mean by "u mean u soldered the stepper internal wires?", redreprap, but I did not open the stepper up myself. I know how easily you can destroy the whole thing that way.

So, looking at your data sheet and the reprap wiki here reprap wiki you apparently need to leave pins 5 and 2 disconnected, pair A is pins 4 and 6, and pair B is pins 3 and 1 as far as I can tell. That would be MY first guess anyhow. Are the pins numbered on the connector of the motor? The diagram on the data sheet shows the pins being from right to left 1 through 6 when the shaft is facing you. I'm curious. Do you have a motor that works on any axis? Seems like the common denominator is the motor wiring (no offense) or perhaps the firmware? I'm having the same problem on my machine but it's just E0 (extruder 1) so I was hoping by your problem getting solved, mine will too. ><Ooh. I didn't see what this gesture was when I chose it. I meant thumbs up! Please please let me (us) know.

Edited 1 time(s). Last edit at 03/31/2013 09:11PM by cncjoe.

Well, this felt stupid.

Took my electronics to a meetup of local 3d printer afficionados, and in the span of like 20 minutes the problem was found to be that I had the motor wired improperly. Unsurprisingly, the coils were fighting one another,which caused the wigglyness. Two wires were swapped, problem solved.

In my defense, I was following the wiring guide I was given properly; it was just given to me for the wrong motor, it seems. Whoops. :/

Thanks for coming back and posting the solution. I have been following this thread since Feb, wondering what the heck could be wrong.