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Steppers stutter or stop when using computer
« on: April 02, 2011, 11:28:03 AM »
I'm sure a similar question has been asked before, but I can't find it when searching.

So the problem is this: Whenever I do anything on the Mach3 computer, be it opening a document or inputting a new Gcode line in MDI, the steppers stutter or stall. They stutter regardless of kernel speed and feed rate, and at higher feed rates they lock up. When I leave it completely alone, it seems to do fine.

The computer is as follows:

Asus P5V-VM DH mainboard (VIA P4M890 chipset)
Core2 Duo E6300 (1.86 GHz)
On-board LPT port
On-board VGA or ATi Radeon X1300

I switched from the on-board VGA to the Radeon based on other posts, but it made no difference.

The signal goes through a KelingInc KL-DB25 opto-isolated breakout board and into PacSci 6410 microstepping drivers.

Any tips?

Offline Tweakie.CNC

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Re: Steppers stutter or stop when using computer
« Reply #1 on: April 02, 2011, 12:50:48 PM »
Hi Novec,

Welcome to the forum.

A problem which is coming up more and more now is that the newer parallel ports only output 3.3 Volts TTL and many breakout boards have opto-isolators which require the old 5 Volt TTL standard.
If you have a multimeter and can measure between GND (pins 18 to 25) and any axis direction pin, then when jogging the voltage should be either 0 Volts (for one direction) or 5 Volts (in the other direction). If you are getting a reading of only 3.3 Volts then check with Keling on the spec of their KL-DB25.
Assuming 3.3 Volts - If you have a  spare PCI slot a 5 Volt parallel port could always be added to your system.

Hope this helps,

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Steppers stutter or stop when using computer
« Reply #2 on: April 02, 2011, 02:28:46 PM »
Thanks, I feel welcome already :-)

I measured the parallel port to just over 5 Volts, so I'm in the clear there. But I have ordered an extra PCI card for encoder inputs or what not, so I can try that one when it arrives if I don't get it working.

Offline Tweakie.CNC

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Re: Steppers stutter or stop when using computer
« Reply #3 on: April 03, 2011, 04:36:04 AM »
There have been other posts where it is not recommended to do anything else with the computer while Mach is running, even moving the mouse can cause problems. I think this is a PC related thing as it is only a few that have this problem.

Tweakie.

Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Steppers stutter or stop when using computer
« Reply #4 on: April 03, 2011, 12:24:26 PM »
Yup, it's definitely PC related, I just can't figure out how. DriverTest turns red sometimes when I do stuff while running it.

I'll see if I can work some of my old computer magic and get things working, or if the PCI LPT board works when it arrives - in two weeks... Otherwise I'll just leave it alone when it's doing its thing.
Re: Steppers stutter or stop when using computer
« Reply #5 on: April 03, 2011, 03:00:21 PM »
It i the same thing when your wife is doing something else, just leave her alone ;D ;D ;D ;D



Jeff
Re: Steppers stutter or stop when using computer
« Reply #6 on: April 03, 2011, 03:45:03 PM »
Good one ;-) Except I'd get booored watching that mill run for hours without anything to do...

Offline Tweakie.CNC

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Re: Steppers stutter or stop when using computer
« Reply #7 on: April 04, 2011, 02:51:37 AM »
Good one ;-) Except I'd get booored watching that mill run for hours without anything to do...

You could always build a wood router   ;D

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Steppers stutter or stop when using computer
« Reply #8 on: April 04, 2011, 05:53:02 AM »
Yup, that's the plan - but it would still run off the same stupid computer. I have all the stepper drivers and other CNC electronics inside the computer case (separately shielded) and run a custom cable with DB37 connectors in each end, so I can run the metal mill, wood router (in the works) and lathe (when budget permits) without shelling out for electronics for each one.

I have an idea about what the problem might be - CPU power throttling. Core 2 and newer processors dynamically adjust clock frequency based on CPU load to save power, and while it works fine with regular programs it might be too slow for latency critical applications like Mach3. I'll test it when I get home from work and let you know how it works.
Re: Steppers stutter or stop when using computer
« Reply #9 on: April 05, 2011, 08:37:55 AM »
No such luck... Disabling throttling in software had no effect, and disabling it in BIOS made the motors stutter constantly. No other BIOS settings made any difference. Disabling WLAN made some difference, but that sorta defeats the purpose. Disabling the print spooler service might have made it a bit more tolerant.

Considering I've tried just about everything there is to try, I'm suspecting the Via chipset on my motherboard simply sucks - it isn't exactly high end stuff. I'll try the LPT board when it comes, otherwise I'll just leave it alone and let it work.