Shielded Cables

[RJS100]

I am using closed loop stepper motor to convert a small milling machine (PM-728). I have read lot of articles on using shielded cables. Both the stepper cable and encoder cable supplied from Stepper Online are shielded, but do not have a drain wire. I was planning on using aviation connectors and connecting the ground to the drain wire to properly ground the shield. Also, my cabinet is non-metallic.

Two questions:

Is there some way to connect the foil sheath to the aviation connectors?
Is this grounding of the shield necessary?

Thanks... Richard

[Dave_C]

Yes, it is possible to ground the foil shield but it depends on what the case of your aviation connector is made of. If it is metal just wrapping the foil around the cable and let the case clamp over it will suffice. Just do this at the controller end and leave the other end trimmed off.

As far as non metallic control cabinets. Not recommended unless they have a foil inner liner. I used non metallic cabinets at Johnson Controls for 20 years but they had aluminum inner liners in the back and on the sides. We built systems with upwards of 30,000 control points using these tying 60 to 100 buildings together for College Campuses, Hospitals, Manufacturing Plants automation systems. No issues if you follow good wiring practices.

Building would get hit by lightning, they would have damage to their stuff but none of our equipment was damaged.

Big fan of shielded cables properly grounded!

Dave C.

[RJS100]

Dave,

Thanks for you quick response. I had the same idea of wrapping the foil sheath around the cable and letting the metal aviation connector clamp around it. The problem is that since the enclosure is polycarbonate with a metal base plate, the metal aviation connector will not connect to ground. Is there an adapter out there that enable you to connect a ground wire to the aviation connector. I guess I could solder the ground wire to the washer portion of the washer/nut that is used to hold the aviation connector to the enclosure. I was just looking for a more professional approach.

Thanks... Richard

[Dave_C]

Dave,

Thanks for you quick response. I had the same idea of wrapping the foil sheath around the cable and letting the metal aviation connector clamp around it. The problem is that since the enclosure is polycarbonate with a metal base plate, the metal aviation connector will not connect to ground. Is there an adapter out there that enable you to connect a ground wire to the aviation connector. I guess I could solder the ground wire to the washer portion of the washer/nut that is used to hold the aviation connector to the enclosure. I was just looking for a more professional approach.

Thanks... Richard

Kind of why non-metal cabinets pose a problem. You will need a common, single point ground in the cabinet. If you get deep into study of radio and electrical issues you can learn what creates a dipole antenna! And that makes EMI noise issues worse!

Automation direct has some good articles on there site regarding this.

Dave C

[martyscncgarage]

The shield maybe grounded at the connectors to the drive.
Just a thought...
Its the way you are supposed to do it when hooking up an encoder cable to Acorn's encoder port. Shield should be soldered to the connector shell.
Marty

[RJS100]

Thanks for your response Marty. I am not sure I fully understand you note. I am connecting the encoder cable (6 leads) and stepper motor cables (4 leads) to a closed loop stepper. Both cables have a foil shield, but no drain wire. Are you suggesting that I solder the foil shield to the aviation connector at the motor side as opposed to the stepper controller side of these cables. I thought that the shield is supposed to be grounded at the controller side?

Thanks... Richard

[martyscncgarage]

Thanks for your response Marty. I am not sure I fully understand you note. I am connecting the encoder cable (6 leads) and stepper motor cables (4 leads) to a closed loop stepper. Both cables have a foil shield, but no drain wire. Are you suggesting that I solder the foil shield to the aviation connector at the motor side as opposed to the stepper controller side of these cables. I thought that the shield is supposed to be grounded at the controller side?

Thanks... Richard

No. I was suggesting that your cables maybe grounded. Sorry, not to imply that they were.

[RJS100]

OK... solder the foil sheath to the connectors and somehow attach a ground to the connector.. That was my plan.... Thanks you very much!

[martyscncgarage]

Most good shielded cables have a drain wire. You'll likely not be able to do anything with foil.

[RJS100]

Sorry, I miss spoke. The cable does not have a foil sheath, it has braided wire. I just found an approach that I have not seen before. Food for thought: