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Motors only turning one way

Posted by Aschie4589 
Motors only turning one way
July 25, 2016 02:59PM
Hey everyone!
After a few weeks of trial and error, and after frying two RAMPS boards, I finally seemed to have a working configuration... except that it doesn't work. So I went back to the beginning and try to do a complete system check up to see if I have faulty hardware somewhere that's frying my boards....
Every part works, but one. Z axis is the problem. When I need it to go up, it will only move down, a fraction of the distance it needed to travel upwards.
I've unhooked everything, and taken a single Pololu driver and the motor wires, and connected them to an Arduino UNO. Using a simple program, I'm making the motors turn 200 steps in one direction and 200 in the other. When connected to the x and y motors, there's no problem, but when connected to the z motors they still only work one way. I'm supplying them with 12 volts.
Anyway, the only thing I could figure out is different from other setups is that the two motors are connected in parallel but with ONLY ONE connector. I figured that this might be a problem (too much current drawn by a single connector?) and might make it not work (?), but then I can't understand why the motors would only go down and not up, instead of not moving at all...
Does anybody have a solution to this? Has anyone experienced the same problem?
Thanks for your help...
Re: Motors only turning one way
July 25, 2016 03:08PM
1. Connecting two Z motors in parallel is generally a bad idea, even though lots of people do it (because they don't know any better) and RAMPS makes it easy to do. Almost all stepper motors used in RepRaps are better connected in series.

2. Have you tried reducing the Z axis maximum speed and acceleration in your firmware configuration?

Edited 1 time(s). Last edit at 07/25/2016 03:09PM by dc42.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Motors only turning one way
July 25, 2016 03:40PM
My problem at the moment is, I basically don't have a printer right now. My RAMPS is acting funny, so I'm trying to wait until I have all figured out to reconnect everything to the board.
How could I connect them in series? Just use both connectors on the RAMPS each for a motor? Thanks for the quick response...
Re: Motors only turning one way
July 25, 2016 03:54PM
Also, what are the advantages and disadvantages of having them in series? I am no expert, so I don't understand...
Re: Motors only turning one way
July 25, 2016 05:00PM
1. Google "wiring stepper motors in series".

2. Plug-in drivers have inadequate cooling for the driver chips, and already struggle to provide enough current to the stepper motors in many systems. If you connect two motors in parallel, then they need double the current to produce the same torque. Whereas if you wire them in series, they need the same current but double the voltage. The stepper motors we normally use only need around 2 to 3V unless they are moving very fast, so if you connect them in series that's 4 to 6V, still well below the supply voltage of 12V or 24V.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Motors only turning one way
July 25, 2016 07:38PM
Ok...
After an evening doing tests I can safely say that I don't understand. I've tested X,Y and E motors and they work with a pololu driver, supplying 12V. I tried the Z motors, and they didn't move. I have found that their wiring is different, because (possibly) they are different motors. I have then connected them in series and tested them once again, and they started working. So I suppose the problem was the current.

Now I'm facing another issue. Note that all of this I have done it without the printer being assembled, just with a multimeter and an old Arduino UNO with some sketches I made appositely. Since I had decided that I was doing a full system checkup, I tested the other pololu drivers. All dead. And this I can't understand: when I received the new board, and connected it, everything seemed to work fine, except for the Z axis. X and Y were definitely working. Then something weird happened, but X and Y still worked. That's when I decided to do the checkup. And now they don't work anymore. At least, the drivers. Luckily I have a few more of them lying around from the previous boards, so I'll be using them. But I don't understand why they wouldn't work.
Sooo... Do you think the problem was the Z axis? I mean, the origin of all problems? Would I be safe to put the printer back together? Or do you think there's something else that I need to check before? Right now I know that the endstops, the thermistors, and the motors are working. I have no way of testing the heaters and fans, but I don't suppose they would be the problem, right? Am I missing something?
Thanks again for helping me through this...
Re: Motors only turning one way
July 26, 2016 07:05AM
I'll leave it for someone with more experience of RAMPS to answer in detail. However, the plug-in drivers do appear to be fragile, they are easily damaged by turning the motor current up too high or shorting them out while trying to adjust the current-setting pot with a screwdriver. Also, never connect or disconnect stepper motors to any sort of stepper driver with power applied to the driver.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Motors only turning one way
July 26, 2016 08:15AM
Thanks for the input!
I was able to reassemble the printer back together, and all the "damage" that I had seen has disappeared (lcd acting funny and thermistors not reading correctly). So I guess the first part of the problem was the current the motors were sucking. Thanks for that!
I am still not able to move the motors up. I mean, I can do that if I disconnect them and use the Arduino UNO, so I'm sure they are not damaged. You said something about the min/max acceleration? How could that affect the direction of the motor?
Re: Motors only turning one way
July 26, 2016 12:00PM
Ok.. a few hours have passed. I have been doing further tests, without reaching much of a conclusion. I was trying to reload the firmware with some of the right settings (fx. number of steps per mm and accelerations), but I'm constantly getting the error (with verbose output):
"avrdude: Version 6.0.1, compiled on Apr 15 2015 at 19:59:58
Copyright (c) 2000-2005 Brian Dean, [www.bdmicro.com]
Copyright (c) 2007-2009 Joerg Wunsch

System wide configuration file is "E:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf"

Using Port : COM3
Using Programmer : wiring
Overriding Baud Rate : 115200
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer

avrdude done. Thank you."

Is there anything I can do about it? Googling only displays more broad cases that do not apply to my PC (eg drivers and wrong port), and I can't figure it out... Is my board broken? (Hopefully not...)

Edited 1 time(s). Last edit at 07/26/2016 12:01PM by Aschie4589.
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