Connecting shield lead to ground

Discussion about the arduino based g-code interpreter, grbl
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scott216
Posts: 226
Joined: Thu Oct 10, 2013 12:35 pm
Location: New Jersey

Connecting shield lead to ground

Post by scott216 » Sat May 03, 2014 11:44 pm

The gshield board doesn't have a terminal block input to connect the shield from the shielded motor cable. Should the shield be connected to ground?
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Simon P
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Joined: Wed Mar 12, 2014 9:17 pm
Location: Wiltshire, UK

Re: Connecting shield lead to ground

Post by Simon P » Sun May 04, 2014 6:50 am

Yes, ideally the conductive shrouds should be connected to ground. This is mitigated by the wires that come with the stepper motors which have no provision for shielding, at least the ones in the full kit don't.

The 'signals' sent from the drivers to the steppers are quite strong relative to the sort of environmental interference we find in our homes so I think that the main source of interference would be from the other stepper wires.

I am not an electronics engineer but recently studied induction as part of a physics course and this is what I understand of it. Perhaps someone who is better qualified can chime in and give us the real low down.
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veng1
Posts: 250
Joined: Fri Nov 30, 2012 12:09 pm

Re: Connecting shield lead to ground

Post by veng1 » Sun May 04, 2014 1:40 pm

A ground line which conducts power needs to be connected at both ends. However, a shield is typically connected at one end only, usually the non-noise generating end. Meaning opposite the motors in this case.

That's where I'd start but if it doesn't solve a noise problem, you can try connecting at both ends. Next, I'd start trying a capacitor or an R-C filter.

If you are picking up noise in a sensor cable, you can also try a ferrite bead which is essentially a single turn or multiple turns through a toroid. Clamp on ferrite beads are great if you have a large connector on the cable but where you have just a wire, the multiple turns get more inductance.

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