VFD interference problem

**JAZZCNC** · 08-03-2016

Originally Posted by Graeme

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** · 08-03-2016

Originally Posted by JAZZCNC

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** · 08-03-2016

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?

**eurikain** · 08-03-2016

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 ?

**eurikain** · 08-03-2016

Originally Posted by JAZZCNC

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.?

I haven't. I have a PCI PP card that I will try to install and use on Thursday, this might prevent the ground loop, who knows :)

**Clive S** · 08-03-2016

Originally Posted by eurikain

I haven't. I have a PCI PP card that I will try to install and use on Thursday, this might prevent the ground loop, who knows :)

It is important as others have said to try a different pp cable or at least check the continuity from pin one to pin one etc at both ends of the cable.

**komatias** · 08-03-2016

Originally Posted by 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 ?

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** · 11-03-2016

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.

**komatias** · 11-03-2016

Originally Posted by 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.

have you got an oscilloscope to probe the parallel port?