Machsupport Forum
Third party software and hardware support forums. => SmoothStepper USB => Topic started by: BarryB on April 06, 2010, 08:44:43 PM
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Hey folks, I'm trying to set up a smooth stepper on a custom built AMD box, and I'm having a devil of a time. I originally set it up on a laptop, which I've gotten it to work on that brilliantly. However, installing Mach on the custom AMD box, the smooth stepper loses connection all the time. If I do get it to be seen at the startup for Mach, it will almost always lose connection as soon as I try to turn the spindle on. This doesn't happen when using the laptop. Any ideas? The computer is closer to the CNC machine, but would that matter? Everything else is in the same spot regardless of which computer drives the card.
Barry
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What else is running on your PC? Anything that hogs huge amounts of processor time has the possibility to delay USB communications. Also, since you say this is a custom AMD box, so you have all the right drivers loaded? Windows will try and do the best it can to find drivers that will work but they may not be the correct ones.
If you loose connection when the spindle turns on it is a noise problem. Spindle motors produce lots of electrical noise and if your turning it on with a relay the relay will also produce a lot of arc noise as well.
Also try a different USB cable. A customer of mine had a heck-uv-a time with a new SmoothStepper that could run for most of a day just fine and then loose connection every few minutes. It turned out to be a bad USB cable.
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The pc is custom built for this purpose. All new athlon 2, 2 gig ram, win xp home premium. It literally has nothing installed on it except xp, Mach 3, lazy cam and the smooth stepper drivers. I don't even give it Internet access unless I'm updating it. I don't think there is any overhead. The USB cable is the same cable I use with my laptop, so it is known good. Half the time the smooth stepper isn't even recognized on the pc. If it is, it is guaranteed to fail if I turn the spindle on when using the pc. The laptop doesn't have these issues.
Barry
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I would not say that the cable is 'known good' as it could be just marginally working on the laptop. Checking with another good quality cable is cheap and easy to do. The symptoms you are describing sound like a bad USB cable. Also, make sure you have all the right drivers for your PCs hardware.
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I've tried with several cables, with all the same result. The drivers are all up to date. Nothing in the device manager has ? on them. I'm able to connect other things to the computer like flash drives or external USB drives if I want to transfer data. I've tried other ports too, all with the same result. I just don't see this working on this computer. Is it finicky? Is Mach3 finicky computer to computer?
Barry
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Are you saying that the SS does not show up in Device manager when it is hooked up? If so what is the status of the three LEDs on the SS?
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No, it shows up in the device manager just fine. It's Mach3 that doesn't see it. Sometimes I have to power down the card, and power it back up. Sometimes that won't work either. It's really odd.
As for the 3 LED's, I'd have to check. I'm at the day job, the CNC machine is the night job.
Barry
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Hi Barry,
You must get to the bottom of the problem when your spindle is turned on. If you don't then you will almost certainly encounter all sorts of strange behavior with Mach and SS in the future.
Is your spindle switched on/off by a relay or a VFD ?.
Tweakie.
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It's via relay. I've been in MN, so i haven't been using the CNC for about a week. I'll try and troubleshoot this weekend. I don't think it's the VFD/spindle though, as with the other machine (laptop) it's tits on perfect. With this PC, I get strange error messages sometimes just by launching Mach3, communication errors, errors seeing the card. Maybe I should nuke and pave and start over on that machine.
Barry
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Hi Barry,
Successful troubleshooting has to be carried out in a well organized and methodical manner, if possible recording the results for future reference - so you must excuse me for asking all the questions.
OK, you are switching your spindle on/off with a relay.
Is this relay switching AC mains voltage to the spindle ?.
Is this relay switching a low voltage DC to control a VFD ?.
Tweakie.
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No problem, I'm happy to have the help. The relay switching sends a DC signal to tell the VFD to turn on a off the spindle. I also have it wired with low voltage DC to control the speed of the spindle. Btw, I'm using the C23 card from CNC4PC which has inputs/outputs for all this stuff directly on the card.
Barry
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Hi Barry,
I have now looked at both my laptops and neither have a protective earth connection (they are both 'double insulated', as far as the regulations are concerned and do not have any connection to the incoming mains supply earth).
Assuming your laptop has no electrical connection between the mains earth pin and the USB or LPT port outer metal screens then this would explain the difference between the behavior of your PC and laptop. One mystery solved I hope.
I will now go and look at my VFD setup and check how it is wired and report back with suggestions.
Tweakie.
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Hmm, I'm not sure I understand. My laptop is connected via 3 prong power adapter. The PC is powered via a 3 prong cord to the wall. Aren't those the same then?
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Not quite the same thing Barry, as the laptop uses an adapter.
If you have a multimeter, with your laptop switched off and disconnected from the mains, measure the continuity between the mains earth pin and the metal part on the outside of your USB connection or the metal part on the outside of your LPT port - Is it an open circuit ?.
Tweakie.
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I'll have to check tonight. I'm at my day job currently;)
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OK Barry, back in communication tomorrow. This means I can go home now ;D. As long as you have the patience we will sort this !!.
Tweakie.
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sounds cool, I'd really like to get that machine running the mill, rather than my lappy.
Barry
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Hi Barry,
After much thought I have compiled a list of things for you to check. I have probably forgotten something important but that's life.
1) All exposed metal parts forming part of a ‘mains operated machine’ must be connected to Earth. [this is more for your own personal safety than anything else].
2) All input devices such as limit switches, estop etc.should be connected with screened cable.
3) The screen of all screened cables must be connected to Earth and only at one end (preferably to one single Earthing point at the controller end).
4) The VFD frequency control input cable should preferably be screened or at least a ‘twisted pair’.
5) The VFD forward/reverse – on/off switching cables should preferably be screened or comprise of ‘twisted pairs’.
6) The cable between the VFD and the spindle motor should ideally be screened and not routed, for any great distance, alongside wiring for inputs (limit switches, estop etc.). [ideally the screen should be connected at the VFD earth terminal only but if the spindle motor is metal bodied the cable should contain a fourth wire for the earth connection to the motor body but the motor itself must then only be fitted to the machine using an insulated mounting to avoid creating an Earth loop].
7) There must be no Earth loops. [typical examples are where the machine frame is connected to Earth via the incoming supply and the VFD is also connected to Earth via the incoming supply and then these two items are fitted in electrical contact with each other thus an Earth loop is formed. The same thing applies with the PC which is also earthed via the incoming supply, if its metal casing parts or its cable screens/shields (LPT / USB etc) come into electrical contact with the machine frame an Earth loop is again formed].
8) Any forms of Radio Frequency Interference (RFI) or Electro Magnetic Interference (EMI) must be traced and eliminated by fitting screening, filters etc. [the EMI is relatively short range but the generation of RFI can be just as much of a problem for your systems as it is to your neighbors computer, TV and radio systems].
9) You should not make any direct electrical connection between ‘the computers Ground wires (pins 18 – 25) or the LPT cable screen/shield’ and ‘Earth’. [the computer ‘Ground’ and ‘Earth’ are to be considered as two separate circuits].
10) If anything here conflicts with any product manufacturer’s recommendations then their instructions take precedence. [they should be a lot smarter than I].
Hope this helps.
Tweakie.
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I'll fix the deficiencies in my box compared to this list with the 2nd control box I build. The first one I have here is temporary 'proof of service' type thing. I think comparing what's different between the lappy and the desktop will be the key though. I'll be doing that this weekend, as I'm getting an art opening ready.
Barry
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My laptop is connected via 3 prong power adapter. The PC is powered via a 3 prong cord to the wall. Aren't those the same then?
Certainly NOT! The output of the laptop charger is very likely floating. The PC is not.
Yes, this sounds very much like a noise problem, and my guess is that the noise source is associated with whatever earthing you have set up between the PC and the machine. Earthing sounds simple, but it AIN'T!
Set up a single central earth bolt somewhere. Make all earth connections radial, direct to this bolt. Do NOT allow any earth loops; do not earth screens at both ends, etc. Use opto-isolation between SS and machine. Twinkie's list is good.
Cheers