Motors moving only one direction
May 01, 2013 10:53PM
Greetings fellow reprappers.

I've been having some issues getting my mendel prusa up and running and was wondering
if a seasoned reprapper could shed some light.

The problem I am having is that pronterface only moves the motors on my mendal one way
(ie. the positive direction) but never the other way. I've tried both fixes for this that I could find
(reversing the motor pins on the RAMPs board and unplugging my mechanical endstops)
but to no avail. Im running sprinter on its default mode, and have yet to get into to the nitty
gritty of refinement. The motor movement seems smooth in the one direction (so faulty wiring
seems unlikely, I've checked my connections a bunch of times). I also searched 'prusa motor
one way' and other keywords to try to find the answer on this forum (it is surely here) but
again no luck.

Any thoughts?

Thanks

Charlie
Re: Motors moving only one direction
May 02, 2013 12:04AM
One way motors are usually a sign of end stop issues.

If you issue an M119 command, what values are returned?

Fl0yd
Re: Motors moving only one direction
May 02, 2013 03:19AM
...and how have you wired your end stops?
Re: Motors moving only one direction
May 02, 2013 05:51PM
Hey Fl0yd,

The end stops have been wired. I plugged them in to the appropriately labelled ports,
and issued the M119 command. They consistantly read x_min:H y_min:H z_min:H, though
I have tried holding any of the stops down to get them to switch, which they don't seem
to want to do.

Are the motors programmed to go only one direction if the end-stops are not plugged in?

Charlie
Re: Motors moving only one direction
May 02, 2013 06:03PM
Hey Waitaki,

I've got mechanical end stops wired as so :

[reprap.org] (the key diagram under Reprap Mega Pololu Shield)

Shows the wiring to be on the first and third pins of the end-stop. I have wired it this way.

Charlie
Re: Motors moving only one direction
May 02, 2013 11:45PM
>
> Are the motors programmed to go only one direction
> if the end-stops are not plugged in?
>
> Charlie

At startup / boot the firmware only allows motion towards the end stop until the end stop has been detected for the first time. This tells the firm where where it's 0 position is and is to prevent you driving the axis out of its range (away from the end stop)

And to simulate end stop contact with your finger you have to press - release - press&hold. ( well o my Gen6d board you do)

Good luck

Edited 2 time(s). Last edit at 05/02/2013 11:56PM by bigfilsing.
Re: Motors moving only one direction
May 03, 2013 05:05AM
Where have you plugged the end stops on the ramps board? Photo?
Re: Motors moving only one direction
May 03, 2013 03:12PM
Ok, after dabbling a bit with the M119 command and pullup settings in the configuration file,
I can see the end-stop switches *tend* to switch when held down. The problem is that they don't
*stay* in their inverted state. Im worried to start the motors up until the switches act consistently
when held down.

The switches again are wired as in the RAMPs 1.4 definition :
[reprap.org]

Could this be due to the absence of a pullup resistor or noise along the wire causing inconsistent
value?

Thanks again for the comments. I feel like I am close to solving this!

Charlie
Re: Motors moving only one direction
May 03, 2013 03:34PM
Do you have 3 end stops wired, or 6? Does the RAMPS board have 6 terminals or 3.

Can you post a photo of your wiring at the RAMPS board?

Fl0yd
Re: Motors moving only one direction
May 03, 2013 05:30PM
The RAMPs board has soldered to it a 2x6 pin header block.
Currently plugged into this block is only the x-axis end-stops
(since I am trying to evaluate one axis at a time before adding
the remainder).

I have five end-stops configured : one for the z-axis, and two
for the x/y axes.

I should add that I can now get the printer to stop when it reaches
the end-stop on one side, but it still won't reverse. The seemingly
inconsistent values are probably sampled and averaged in sprinter
to yield a consistent result, yes?
Attachments:
open | download - Endstop-Wiringlow.jpg (154.2 KB)
Re: Motors moving only one direction
May 03, 2013 09:16PM
Bit puzzled by that picture..
You only need 3 connections, first one is x axis, then a gap, then the y axis, then a gap, then the z axis
Re: Motors moving only one direction
May 04, 2013 12:08AM
If you try to wire it with only 3 end stops (X,Y,Z), each in the home position for the given axis, does the behavior change?

That would follow Waitaki's wiring suggstion of first 2 pins, skip 2 pins, ...

Fl0yd
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