Stepper motor moves one way only.

I am test driving my stepper motors, alas, nothing is that simple...
Symptoms include only positive movement and PSU fuse blown twice.

I have soldered together my Sanguinololu 1.3a board, which has Sprinter firmware already installed on the Atmega644P chip. My laptop has Printrun installed on Ubuntu, (http://reprap.org/wiki/Printrun I followed these instructions)

Here is what I did, (warning, quite detailed):
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I just had one Genuine Pololu stepper driver placed in the x axis slot. When I powered up the board, I set the Vref ~ 0.3 V.
I then powered off, plugged in a stepper motor, powered up which blew a 1A fuse in the PSU output, powered off fast...
Replaced 1A fuse, powered up again with steppor motor unplugged, reduced Vref ~ 0.1V. System seemed stable so powered off.
Plugged in stepper motor, powered on and plugged USB cable to laptop, started up pronterface and connected.

I could send +x movement but not -x. At least the software could talk to the board. Vref was moved back up to 0.3V which worked fine.

I powered off and unplugged USB and stepper motor. Said stepper driver was moved to y-axis slot, powered up, Vref ~0.3 checked.
I powered off, plugged stepper motor in, powered on, plugged USB cable, connected with pronterface and only +y moment was possible.

Powered off, removed said potentially faulty stepper driver, put new stepper driver in x-axis slot. USB and stepper driver was unplugged.
I powered on, led flickered again, powered off fast... PSU's 1A fuse had blown again.

1A fuse replaced, powered on, Vref set to 0.3V, powered off.
Plugged in stepper motor, powered on, plugged USB, connected with pronterface, only +x movement possible.
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My observations:
That's two stepper drivers involved in a fuse blowout. One when the stepper motor was wired in, one without. Both were in x axis slot so there may be a short in that region, I don't want to risk my fresh stepper drivers testing fuse blowouts on y z and e axis =) Only positive movement successful but motor did hold its position.

My questions:
How could I diagnose my stepper drivers to make sure they have not been damaged?
How should I diagnose my Sanguinololu board around the x axis slot?
Is there another way I can double check the firmware/software side of things to check everything is ok?

You need to either hook up your endstops or disable them in your firmware (or invert them).

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Very good point, thanks =)

I jumped pins 1 and 3 on the end stop molex connectors. So yes I have movement in both directions!

The fuse blowings is still a mystery...

1A is far too low for a RepRap, you need about 5A without a heated bed.

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[www.hydraraptor.blogspot.com]

I know =) I thought 1A would be OK for testing out one stepper motor on its own. I was being paranoid since I was using an undocumented motor I found lying around. I'll use a bigger PSU for everything.

The mystery is why the fuse would blow when I didn't have the stepper motor connected. It's probably not worth pursuing for now since the motor does behave now.

Would you say the current usage for a RepRap is roughly:
4x1A from stepper motors
3A from hot end
8A from heated bed
? I thought that might be useful to put on the Sanguinololu page on choosing a PSU

The average supply current is less than the motor current because the chopper drives are only on for a short time.

Most repraps have 5 motors, not 4, and possibly a fan.

The hot end is usually a 6.8R or 5.6R resistor so about 2A. Prusa style PCB heated beds take about 10A when cold.

So I would allow 10A for the bed and 5A for everything else. A 16A - 20A supply is about right.

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[www.hydraraptor.blogspot.com]

The two z motors would be in parallel so I would have though half the current goes through those ones.
But useful to know, thanks =)

I also have a issue with X-Axis going in only one direction.

I'm using the latest ver1.3b PCB with a SMD Atmel

doesn't seem to make any difference if I have the endlimits pulled low or high or inverted in software. I have swapped the Pololu stepper drivers around as well as the motors but still no change.

I measured the X-direction pin and it's always 5V. I have checked the track all the way back to Atmel and has no shorts to 5V line any where.

So it has to be software or a blow Atmel.

Should I try Teacup firmware instead of sprinter?

- EDIT -
I think Ijust found the issue...
[forums.reprap.org]

Edited 1 time(s). Last edit at 08/20/2012 08:11AM by Glennbot.