Wave drive? Type???

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16 Feb 2011 17:34 #7250 by ehud42
Wave drive? Type??? was created by ehud42
I'm trying to reduce some 'slippage' on my (crudely homemade) machine. Initial I was using stepgen type 9 to drive the x/y axis, however, I have been noticing a drift in one of my axis. The drift seems consistent enough to suggest I'm loosing steps in one direction only.

One of the things I tried was changing from 1/2 stepping (type 9) to full stepping (type 5). This almost seemed to make things worse as there was now clearly random / intermittent slippage (I could hear the stepper 'jumping'), even at reduced feed rates. In monitoring the i/o pins it appears that type 5 is simple full step, one pin at a time stepping. I would like what I believe is called wave drive full stepping. This is where there is always 2 pins active, but still only full steps are taken.

1 - 1100
2 - 0110
3 - 0011
4 - 1001
etc.

How do I configure this?

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16 Feb 2011 21:21 #7262 by andypugh
Replied by andypugh on topic Re:Wave drive? Type???
It is _probably_ electrical noise in the signal wires, or maybe a weak 5V from the P-port. Trying to fix it with a different step pattern might be the wrong tack.

Try 5V pull-ups at the driver inputs (1k, or 2.2k sounds about right) and see if that helps.

To answer the actual question asked, the development version of emc2 allows you to define your own step patterns (Step type 15) However I am not entirely sure how it is done.
www.linuxcnc.org/docview/devel/html/man/man9/stepgen.9.html

As it is in the development version you might actually need to look at the source code to figure it out.

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17 Feb 2011 02:32 #7269 by ehud42
Replied by ehud42 on topic Re:Wave drive? Type???
I'm not sure where I found it (searching at work), but I stumbled across some information that suggested type 6 is the wave drive I'm looking for. I tried it tonight, and
    It is the wave drive
and
    it seems to have solved the drifting problem.

I'm still not sure why it fixed it, other than the wave drive provides maximum torque since there is alway one coil energized while moving and two while standing still. I was noticing that the stepper did not seem to have a lot of torque using type 9 (half stepping), and type 5 was even less torque.

How does the documentation get updated? The page you mention should be updated to state type 6 is wave, and type 5 is not.

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17 Feb 2011 13:41 #7283 by BigJohnT
Replied by BigJohnT on topic Re:Wave drive? Type???
Any developer with push access can update the docs. I could do it but I don't understand what a wave drive is or know what a type 6 is exactly so I'm at a loss there... A note on the developers mailing list or on the developers irc might get it done... I'll do the irc one...

John

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17 Feb 2011 14:28 #7284 by ehud42
Replied by ehud42 on topic Re:Wave drive? Type???
The page I found the information on is:

wiki.linuxcnc.org/cgi-bin/emcinfo.pl?act...se&diff=1&id=Stepgen

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17 Feb 2011 14:54 #7286 by andypugh

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