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Author Topic: Stepper glitches fwd and rev  (Read 2331 times)

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Stepper glitches fwd and rev
« on: October 18, 2016, 12:08:20 PM »
I'm having a little problem, 570oz nema 23 motors with digital drives and a ess board..

If I send increments of .0005 moving toward one direction I get exactly that but when I try sending it back in the same .0005 increments the stepper goes fwd still one or two steps and then goes the correct direction..

Tell it to go fwd goes fwd tell it to go rev and goes fwd then goes reverse ?

Any idea why this could be happening possibly tuning the motors some ?

I'm going to try another drive today and check the pulse from the ess to see if it is sending mixed pulses maybe ? 

Thanks, Horasio
Re: Stepper glitches fwd and rev
« Reply #1 on: October 18, 2016, 11:02:08 PM »
Sounds like a timing issue between the time the DIR line changes state and the time the first step pulse is sent.  Most stepper drivers require a minimum time  (5 micro-seconds on mine) from the time the DIR line changes before a step pulse can reliably be applied.  If the step pulse arrives too soon, the first pulse (or even two perhaps) will spin the motor in the wrong direction.  Since it is happening only when switching from forward to reverse, I'm guessing your system is probably using a low signal for the forward direction (active low) and a high for the reverse direction.  I say this because a system can often sense a low (ground/reference level) quicker than it can sense an applied voltage.

I'm not sure how to adjust this since my system is off-line at the moment, but perhaps someone else will chime in on what to change/set to adjust this timing.  But I'm pretty sure that is what is happening at the very least.

Stephen "Highspeed" Kruse
Re: Stepper glitches fwd and rev
« Reply #2 on: October 19, 2016, 12:23:22 AM »
Thanks for your help problem solved, I had enabled backlash compensation on the z axis on a lathe and I took me sometime before realizing this I swapped out the z axis with x axis drive and it keep doing it then I used the axis to move the z motor and it stopped doing this, so I started going through all my settings and backlash was enabled for z axis .. Disabled and it is working great ...

« Last Edit: October 19, 2016, 12:25:17 AM by Horasio310 »
Re: Stepper glitches fwd and rev
« Reply #3 on: October 20, 2016, 02:53:19 AM »
Ah, yep. I can see how that would do it, too.

Thanks for following up with the fix.  It's in my notes now.