VFD interference problem

[JAZZCNC]

Jazz, I'm not sure to understand what you are saying... will the ESS fix the issue IF it is a ground loop going to the PC ?

I have tried getting rid of the ribbon cable. Same problem, though I had disconnected the X axis motors because I didn't want to twist the gantry. But then it was a little more difficult to hear the noise but it was still there. I will do some more tests on Thursday, I'll connect everything back together to get the maximum noise, then disconnect the DB25 cable and see if that stops it. I'll let you guys know ASAP.

In theory yes it should but like been said depends if this really is the source of trouble.? That said I'd still change the BOB because it's clearly not very good because shouldn't happen even with parallel port.

Now like Clive ask's What Noise.?

I think you miss under stand what is meant by Noise. It's not audible so if your hearing any noise that's something else.?
If your using AM Digital drives then I suspect it's because you haven't tuned them. Or what your hearing is the current reduction in the drive working while motors are stood still. This will make an Hissing sound.

Electrical noise or EMF is a Silent Killer.!!

Very difficult to help from distance when it comes to noise. All you can do is be meticulous with wiring and gnding. Ensure separation between signal and power cables.
If still present then fit EMF Filters etc.

If still present then start back tracking.

[Graeme]

I was helping (well trying) to help Geoffroy over the weekend with his "noise" issue. His current problem is that when he runs the spindle all the steppers start making random moves. It is these rapid random stepper moves that is the noise he is hearing.
We started looking into the shielding of the spindle cable and he managed to improved it, but no change to the random stepper movements. He then removed the VFD unit and all VFD wiring from his control cabinet -still the same issue. So it does not look like it is caused by the cable radiating noise into the BOB.
The last thing we tried was to disconnect the parallel port cable from the BOB. This did seem to stop the steppers from moving when the VFD was run.
The reason I suggested he disconnected his slaved X axis motors was when the spindle was run these motors were sometimes going in opposite directions causing his gantry to twist. Removing them kept his machine safe, but did lower the "noise" from the steppers.
It looks like the BOB is seeing noise on the signals from the PC when the spindle is run, which is then being used to send random STEP and DIR pulses to the stepper drivers. This could be caused by an earth loop between PC and control cabinet or by a poor 0v connection between the two. More testing will be required to find out which.
Hope that clears up the meaning of the "noise", any suggestions welcome as to how to solve this one.

[eurikain]

Thanks Graeme, you couldn't explain it better :)

[cropwell]

You may well have a ground loop, however you would do well to relocate your BoB so that the PP cable from the computer plugs directly into it (get rid of the unshielded flat form cable).

A good principle to follow when wiring up a cabinet is to put signal cables on one side of the cabinet and power cables on the other.

Cheers,

Rob

[eurikain]

This is how the cabinet is set. All hight voltage power cables are on one side of the cabinet. Signal cables are close to the BOB, there is only 5V power cables that run next to them.

I'll get rid of the ribbon cable, but that doesn't solve my ground loop. Why would I have a ground loop while other don't ? Is it the computer that's the problem ?

[komatias]

This is how the cabinet is set. All hight voltage power cables are on one side of the cabinet. Signal cables are close to the BOB, there is only 5V power cables that run next to them.

I'll get rid of the ribbon cable, but that doesn't solve my ground loop. Why would I have a ground loop while other don't ? Is it the computer that's the problem ?

I think it is down to the fact that many use metal cabinets to house the electronics and also for the machine frame. Spurious currents then have an easier path to earth.

[eurikain]

I confirm that it is a ground loop. I changed the parallel port today using a PCI card I have. Same noise issue. Disconnecting the PC fixes the issue.

[JAZZCNC]

The last thing we tried was to disconnect the parallel port cable from the BOB. This did seem to stop the steppers from moving when the VFD was run.

Does the BOB have Charge pump.? If so then disconnecting from PC will kill the Outputs so you won't get any movement.!!

Going to sound obvious but have you tried another parallel port cable.? Also you are using a proper straight thru cable not some Old printer cable.?

[cropwell]

Does the BOB have Charge pump.? If so then disconnecting from PC will kill the Outputs so you won't get any movement.!!

Going to sound obvious but have you tried another parallel port cable.? Also you are using a proper straight thru cable not some Old printer cable.?

Hi Jazz,

This BoB does not have a charge pump. I have suggested that the OP uses the cable that came with the BoB (these are generally sold with PP and USB cables) if there was one. Also that flat PP cable inside the box needs to go or at least be shielded.

Cheers,

Rob

[komatias]

Goffroy,

you did some work on the spindle if I remember from your other thread. You sure that the grounding is still intact in there?

Also I cannot tell from your photos if the shield of your stepper motor cables is grounded. Each of the sockets in the control box should have a solder tang to allow them to be grounded too unless they are designed to be used with a metallic box.

Finally, is your actual house wiring set up correctly with a good ground to real ground?