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Strange movement behaviour
« on: December 01, 2013, 08:17:53 AM »
Hey all, new to the forum here. Im building a Momus 2.1 CNC router and have had my share of the building woes. The latest of which really has me stumped and its very weird.
I can move my Y axis just fine by itself. I can move my X axis fine by itself. The trouble starts when trying to move them together. If Im manually jogging the machine the Y is fine. The X will move in the positive direction but will not jog in the opposite direction unless I nudge the Y positive just a bit. I know Im not doing very well explaining here but I guess the easiest way to say it is, I cannot get the X to return the other direction unless I FIRST move the Y a bit in the positive. Weird right? I can move the X all day back and forth until I move the Y in the negative, then the X will only move one direction. If I then nudge the Y positive, the X takes off again.
Im suspecting my BOB since I have had some other troubles with it and it is the cheapo one that comes with a 3 axis kit.
My setup is as follows:
DM524 drivers
425 oz/in Nema 23
Mach 3 Trial ver. (Waiting for Mach to send me my License code)
Windows 7 32bit
1.6 Duo core: 2 GB ram


Offline ger21

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Re: Strange movement behaviour
« Reply #1 on: December 01, 2013, 10:04:44 AM »
Measure the voltage on your dir pin when the trouble occurs. It should be 5V in one direction, and 0V in the other direction. Measure at bot the parallel port and the breakout board.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Strange movement behaviour
« Reply #2 on: December 01, 2013, 11:06:54 AM »
Well I think this is my problem then. I only see 2v on any of my direction pins when I read it with my meter and jogging.
Im thinking my BOB is a POS. Earlier today I had good movements on the X, then it stopped working altogether so I moved the X to pins 8 and 9 from pins 2 and 3. X started working again.
I was using cheap alarm wire 22/4 for my connections. I thought this might be introducing some problems so I just spent the last hour and a half rewiring the system with shielded 18awg cable. Everything is individually shielded. Now I cant get any smooth movements at all from any axis. The Y is all jerky and sounds horrible like something is grinding against something else. If course I checked and its freely moving by itself.
So now I have no movement on the X, jerky movement on the Y and still no idea why.....
I only have the 1 parallel cable to I cant check that but it and my BOB is the only thing I can think of as to the cause of this. Unless my printer port is not putting out 5v for some reason.

Some good news, I got my license from Artsoft, I feel all official now!!

Offline ger21

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Re: Strange movement behaviour
« Reply #3 on: December 01, 2013, 11:21:30 AM »
Unless my printer port is not putting out 5v for some reason.


You need to check the voltage at the port, or at least at the end of the cable to narrow down the issue.
A lot of newer PC's have 3.3V ports, which may not be enough for your drives.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Strange movement behaviour
« Reply #4 on: December 01, 2013, 11:37:44 AM »
Unless my printer port is not putting out 5v for some reason.


You need to check the voltage at the port, or at least at the end of the cable to narrow down the issue.
A lot of newer PC's have 3.3V ports, which may not be enough for your drives.

If this turns out to be the case do I have any options besides another computer?

Offline ger21

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Re: Strange movement behaviour
« Reply #5 on: December 01, 2013, 11:52:29 AM »
Yes, you can get a buffered breakout board that ups the voltage to +5V.
http://www.cnc4pc.com/Store/osc/product_info.php?cPath=33&products_id=45
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Strange movement behaviour
« Reply #6 on: December 01, 2013, 11:59:26 AM »
Ok this is more than likely my problem or at least part of it. After taking some readings directly off the printer port on the back of my PC here is what I found.
Pins 10-13 read 4.3V
Pins 14 and 16 read 3.3V
Pin 15 read 4.3V
No other pins gave me any reading at all. None read 5V.
Hhhmmmmmmmmm




Offline ger21

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Re: Strange movement behaviour
« Reply #7 on: December 01, 2013, 12:02:30 PM »
You need to measure the DIRECTION pins WHILE your jogging.

pins 10-13 and 15 are input pins only, and don't really have anything to do with the issue you're having.

If pins 14 and 16 are 3.3 volt, then your direction pins probably are as well.

Do your drives support 3.3v signals?
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

Offline ger21

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Re: Strange movement behaviour
« Reply #8 on: December 01, 2013, 12:03:37 PM »
Also, what are your pulse widths set to in the motor tuning screens? Make sure they are at least 5, and try 10-15 and see if it makes a difference.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Strange movement behaviour
« Reply #9 on: December 01, 2013, 12:19:24 PM »
Not sure if the drives support 3.3 or not. They are cheap asian drives, Longs, Wantai etc.