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Author Topic: Hybrid Stepper Setup in M4  (Read 2103 times)

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Re: Hybrid Stepper Setup in M4
« Reply #20 on: December 05, 2018, 04:38:45 PM »
Craig I got after this again a bit here today and damn if I'm not tree stumped again...I have this ever so strange...offset I guess is the best way to describe it...I dial in the correct amount of steps to get the desired travel and then each time I go back and forth I shift ever so slightly shift in one direction...I set my test app back on a drive and bingo everything is spot on...back in Mach and 3 sheets in the wind...

i can just watch my counter in a terminal app...start at about 1~3 go 3997~4002 then cycle again I'm 18~22 and 4024~4030...just keeps sliding...
Re: Hybrid Stepper Setup in M4
« Reply #21 on: December 05, 2018, 05:05:14 PM »
I uploaded a video to Youtube

https://youtu.be/eh2Lx2pX8bU
Re: Hybrid Stepper Setup in M4
« Reply #22 on: December 06, 2018, 01:36:13 AM »
Hi,
I would say that the stepper is losing steps some where or you have some weird backlash fault going on.

Its not impossible that you are losing steps.....I know you are going to jump up and down that closed loop steppers don't lose steps....
but they do. Eventually if it loses enough steps then it should fault 'following error' It may be that your error window is wide enough that it can lose
steps without throwing a fault.

The other possibility is that the signaling rate is such that pulses are getting lost or not recognized. You will recall that I recommended a fairly low
microstepping regime ( 8 micro steps per fullstep) in order that the pulse rate be low and therefore communication problems between the controller
and the stepper be strongest or least prone to error. I suspect that your 57CNC has singled ended step/direction outputs whereas the Ethernet input
of your stepper is differential. You may have to fit line drivers to your 57CNC step/dir outputs.

Craig
My wife left with my best friend...
     and I miss him!
Re: Hybrid Stepper Setup in M4
« Reply #23 on: December 06, 2018, 08:52:19 AM »
I certainly do believe it IS possible for these to lose steps...they have this HMt technology built into them and I don't believe its such a great thing to have any more complications with conflicting parameters in S/D mode...perhaps I am wrong and will investigate that as well but I have the step compensation shut off...I'm simply looking at the counter cycles to gauge distances and identify issues.

I would be a complete bone head asking for advice, getting it and not using it so I have them set to 8X (4X as well)and kept V and A very manageable and after several hours of repeated crossing of the over/under threshold in distance/MS unit tuning....I mean I set the distance at one complete counter cycle and tuned to where I crept up on the exact distance...reached it and exceeded it but in none of my efforts was I able to repeatedly go the distance and return to dead zero and then go back out the exact distance...the video is the result of what I felt was the correct MS...
 I know we covered this but I am not in any way using Ethernet as a control...just a config...the inputs should be just like a driver...I am however of course using the internal drivers and perhaps it's some clocking issue...I'm reaching...lol

I have a ticket in with Mach and we'll see where that goes and I'm going to get my contact at Schneider again today or tomorrow and see what they might have for me.

Thanks as always!!!
Re: Hybrid Stepper Setup in M4
« Reply #24 on: December 06, 2018, 12:24:44 PM »
Hi,

Quote
I know we covered this but I am not in any way using Ethernet as a control...just a config
I suspect that the electronics behind the Ethernet input are differential and must therefore be driven by differential signals
whereas the output of the 57CNC is either open collector or totem pole TTL output. I'm wondering if the mismatch in signals
is causing some to get lost.

Craig
My wife left with my best friend...
     and I miss him!
Re: Hybrid Stepper Setup in M4
« Reply #25 on: December 06, 2018, 03:22:10 PM »
I have tried all the various combinations of settings for MS and they all result in the exact same drift...ugh
Re: Hybrid Stepper Setup in M4
« Reply #26 on: December 07, 2018, 12:53:32 AM »
Hi,
try linedrivers.

Craig
My wife left with my best friend...
     and I miss him!
Re: Hybrid Stepper Setup in M4
« Reply #27 on: December 07, 2018, 09:25:33 AM »
Quote
"try linedrivers."

A very interesting idea....Thanks Craig!

I looked further into the settings and it seems in addition to step and direction I can set S/D inputs for EncA/EncB with Follow so...perhaps that's an possibility....checking with Schneider this morning....can I drive them with the pokeys on an encoder setting is the big question I guess.

I ran my general internal app again across a wide array of MS Settings from the default 256X down to 2X and while the drive certainly changed characteristics and pitch it never lost a bit of accuracy...something very odd going on because it is just so clocklike predictable.
Re: Hybrid Stepper Setup in M4
« Reply #28 on: December 07, 2018, 10:59:28 AM »
Hi,

Quote
I can set S/D inputs for EncA/EncB with Follow so
No, that is not what I mean.

The output of the 57CNC swings from 0V to 5V. The Ethernet input is expecting a balanced signal with one wire -2.5V while the other wire of the
pair is 2.5V. You need an electronic circuit to convert the single ended output of the 57CNC to the balanced (differential) input of the stepper.
A 74HC244 should do the trick.

https://uk.farnell.com/texas-instruments/sn74hc244n/ic-buffer-line-driver-74hc244/dp/9591281

Craig
My wife left with my best friend...
     and I miss him!
Re: Hybrid Stepper Setup in M4
« Reply #29 on: December 07, 2018, 11:21:02 AM »
Hi,
sorry just looked at the data sheet for that IC that I linked to....its single ended output as well.....this should be correct:

https://uk.farnell.com/texas-instruments/sn75lbc172n/ic-quad-diff-line-driver-16-dip/dp/1755261?st=diferential line driver

Craig
My wife left with my best friend...
     and I miss him!