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Author Topic: Steppers slightly "jitters" when idle  (Read 3348 times)

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Steppers slightly "jitters" when idle
« on: January 09, 2011, 12:04:59 PM »
I am noticing that my stepper motors slightly jitters when mach3 is idle.  Less than .005".  It is mostly the x or y axis.  i have solid movement when running, no issues.

I think the issue is related to the PC doing something in the background and I do not think it is noise.

is there any way of looking to the LPT port to isolate the PC? I am thinking I should disconnect the LTP cable to verify noise??

Running AMD Atholon with 1.5GB memory. two LPT's with AMPI stepper control.

Thanks,

Phill

Offline Hood

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Re: Steppers slightly "jitters" when idle
« Reply #1 on: January 09, 2011, 04:19:05 PM »
A scope would be the best option as you would soon see if there was noise etc. Disconnecting the cable may help but if you have enables then you would need to rig something up.

Hood

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Re: Steppers slightly "jitters" when idle
« Reply #2 on: January 10, 2011, 06:39:05 AM »
What does the driver test look like?

RICH

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Re: Steppers slightly "jitters" when idle
« Reply #3 on: January 10, 2011, 09:42:51 AM »
are your drivers getting hot?
Mr. Creosote
Re: Steppers slightly "jitters" when idle
« Reply #4 on: January 12, 2011, 05:24:12 PM »
I had this problem a couple of years ago, It was resolved by selecting low active for the axis motor drives in ports and pins. Now using smooth stepper it doesn't appear to matter whether they are active high or low.

Neptune
Re: Steppers slightly "jitters" when idle
« Reply #5 on: January 14, 2011, 12:29:04 AM »
Thank you for the feedback.

I have not thought about the heat so I will check by starting cold or checking with temp with sensors.  

Regarding the active low.  I remember when I first hooked up the stepper motors they did not work with active low but I will re-check.

i do have the AMPI drives maxed out on amps and the motors are hot. I do not have the drives to reduce current consumption when idle.  I maxed out the current since I wanted the motors to move rapidaly and be accurate.  Since i have acme screws the current in the drives could be reduced.

What stands out most to me is not hearing about random pulses being generated by mach3 or the PC due to software conflicts.

More to test.  for now I stop and zero everything then check position and cut.