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axis controller only goes one way

Posted by letsburn00 
axis controller only goes one way
February 12, 2009 08:15AM
I've built my machine, electronics and have assembled the whole things. I'm testing each axis individually but have a problem. I often run into the issue that I can run the driver to say 50mm and the axis will push out to that point. But when I try to pull it back to say 10 mm, the lights on the board flash for a single moment, then stop. Pressing ht home button does the same thing. So I can only push it out to a certain point, but not back. Any ideas. I've tried unplugging my opto-switches and new switches to no avail;. Have I forgotten something?
Re: axis controller only goes one way
February 12, 2009 08:37AM
Lots of people report this and it always seems to be a problem with the optos. Either the firmware is compiled for the wrong polarity or they are plugged in the wrong way round. Try blocking the opto and see if you can then move it both ways. That would indicate a firmware polarity mismatch.

Re: axis controller only goes one way
February 12, 2009 05:21PM
On the PIC electronics, the three pin connectors on the stepper board that connect to the end-stops, are wired with the signal as the middle pin, and +v and 0v as the outside pins. When I had a similar problem, I removed the opto-electronics completely from the picture by placing pc 'jumpers' onto these connectors.

I'm not sure if the connections are the same on the arduino electronics.
Re: axis controller only goes one way
February 12, 2009 06:26PM
Is the requirement for a home function massively important? I know that it needs to zero at the start of a print, but otherwise can it work? Or will calibration drift significantly in a short time?

I did test each opto a few months ago to see if they worked using the test program, I had few problems. I think I'll have to check them again tonight.
Re: axis controller only goes one way
February 13, 2009 08:59AM
Yes it is important.

The current position is not stored permanently so as soon as you switch the machine off it needs to recalibrate itself using the homing switches.
(just like your inkjet does)

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