Thread: stepper motors glitching
This is my first post here - thought that since I lived in the UK I should support this one rather than some overseas ones .
I'm part way through my second cnc router build (I will post this at some point for interest) and thought I'd take the opportunity to resolve an issue with one of the stepper motors. The x axis was basically glitching quite frequently during traversing. My set up is:
Driver board System3 all in one - Roy DIYCNC
3Nm steppers x & y - ArcEuro
1.8Nm stepper z - (sorry,can't remember where from)
Power supply 350W 33V - Roy DIYCNC
Desktop PC with parallel port.
After doing extensive testing (step width, pulse width, ramp rates, swapping motors, axes etc. different step rates etc.) I concluded that it was the X axis driver circuit. The charge pump signal had also stopped working some time ago, and needed to be overriden to get the board going again. I wrote to Roy and he suggested sending the board back to replace the allegro chip. It is now back with me, as a complete new board , and bench testing shows that now all 3 axis are glitching!
I started to wonder about the data from the PC so have borrowed an oscilloscope and checked the pulses out of the end of the parallel cable (i.e not connected to the driver board). During a steady traverse (me pressing the left arrow for example) they show square regular spaced pulses (I'm triggering off the pulse to make it easier to read), but quite often the spacing of the next pulse varies considerably. This means that the PC is the source of the glitching.
I've only discovered this tonight, so have alot of things to check, but though I'd ask for ideas on this one?
The PC had a fresh XP install, with only Mach3, a CAD program, Vectric Cut2D, and AVG (virus checker). It is on the internet, but it still glitches even it is not. I've not checked all the processes which are running in the background, but the Mach3 diagnostic screen shows 'Int time' around 10. Sorry this info is a bit sketchy, I need to do more on this.
I'm sure someone else must have had this issue. Reason for pursuing it is because complex jobs seemed to be loosing steps in the X direction and the 2 issues seemed linked.
p.s. Also have an extra parallel port in the PCI slot which I've not used yet (was intended for further inputs etc). I briefly had a play with this to see if I could run it all from here in case the main parallel port was broken, but could not get motion. Didn't have time to investigate tonight. Thoughts on trying this route welcome.
Welcome to the site Barry, Hum "but could not get motion" I’m not the best tool in the box but I would say try taking that PCI card out and see if that helps. I'm just thinking maybe its conflicting with the main one, I’m not 100% sure but I think I read somewhere that some PCI cards have given issues, I could be wrong but if you can get time to remove it then you may as well.
The guys will be along shortly and hopefully have better solutions to offer you, welcome to the site anyway and good luck!.Me
Thanks for that. When I said could not get motion, that was only last night when I plugged it into the additional PCI parallel port as a trial. When it is plugged into the main parallel port all steppers move fine, except for the glitching which I think is leading to lost steps.
The glitching has been there from day one (about 1.5 years ago) long before I added the second PCI port card, so I think this is OK, but will remove anyway as part of the trial.
There must be something upsetting the pulse output from the PC. I've got some ideas but as this is a hobby it will have to wait for the next window.
Suggestions welcome !
I don't use Mach3 but I'd suspect AVG or possibly the video driver. Installing EMC2 on several machines showed poor latency with inbuilt video drivers so it might be worth sticking in a video card if you have one handy - I had a Matrox lying around which is recommended for EMC2 and it helped considerably.
The video card idea is worth looking at, hadn't though of that. I bought the MB from a colleague who was into music creation. He wasn't bothered about the video card, and it might even be on-board video. It was over a year since I built this machine so I will check tonight. If it is on-board, or low spec, an upgrade would be worth a try.
I think this latency is the route of my problem, just a matter of finding out the cause. If it is AVG then that would be annoying since I would have to drop internet access on the garage machine, which is quite useful.
The processor was reasonably good, an Athlon XP 2600, and I put in a fair bit of ram. MB was a well known make.
I'll post back if I find out any more, thanks. Other suggestions welcome . . .
Still haven't checked the video card, but managed to run a few more quick checks last night. Attached is a photo of the oscilloscope display when connected to the parallel port lead, pin 3 (x steps) during trraverse. First photo shows scope with even spaced pulses, second photo shows the glitching of uneven spaced pulses.
I'm also have a video of the steppers running. I will post later, and you can hear the glitching.
Screen shot of DriverTest program, shows all is well.
Also switched off Virus checker, and set it up to trust Mach3. Made no difference.
I don't use MACH because Windows isn't a friendly enviroment for stepping. Don't know if this will help, but on my PC pressing Cntl-Alt-Delete brings up the XP Task Manager. Check the "Performance" tab and see how flat your CPU usage graph is. Parking a jittery mouse slightly past the screen bottom right hand corner can help smooth it out.
You could try the EMC2 trial disk (http://www.linuxcnc.org/content/view/21/4/lang,en/) which would help determine whether it's hardware or software.
It's interesting that Mach3 appears to think the PC is ok but there are problems in operation. How long did you run the test and what other system activity was there?
The EMC2 latency test suggests running it for a while and stressing the system at the same time.
Will the scope capture to a file? - it might be more instructive to see a series of pulses.
I did pull up the task manager and took a screenshot of the processes running, and nothing stood out as odd. I'm at work so don't have this picture, but will post it later in case anyone spots anything. I didn't try the CPU useage graph, but will have a look.
In terms of Mach3+windows, I know there are many happy users running this combination so I should be able to get to the bottom of this, although I accept your point about Linux.
I'll have a look at EMC2 as part of the investigation. Should tell me where the problem is/is not. I ran the Mach3 test for about 20 seconds, and Mach3 was minimised and not cutting, but nothing else. I should try this with more things running, and for longer, and see what happens.
I'm working on a way to capture the scope data since this would be a great help. Once I get the stepper video posted on youtube (never posted video before), it should help some of the experts out there to offer a solution.
Another thing I'm going to try is to look at the signal off the parallel port directly at the motherboard. My scope data was from the end of the parallel port cable. I have read about suspect cables, and I'm hoping it is as simple as that because it would be easy to fix!
Thanks for all the suggestions so far, there are more things to try than my hobby time allowance allows (don't ask!) but I will get through them all in the end.
It dose say on the MACH website:
- Non-integrated Video Card with 32MB RAM
Something that maybe worth trying (as you can leave them running and come back) is some system stress test software's. This will max the PC out for hours and report back to you how it did, I think if you are running an integrated graphics card then I would look at running a memory testing program just to be sure the RAM is ok, memtest86+ I use here on new builds and with it being an older system....let me know if you need a download link for this. The system stress test software i use is called Prime.
I would consider removing AVG as well, if your other system has got an antivirus on it then you could just use a USB pen drive to move files about, I understand though as internet access/ local LAN is handy to have if everything is working ok..Me
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