And the shield on the stepper motor cables? Should I connect it to earth ground?
Envision EMI or noise as snow falling to the ground. It's every where but mostly it's comming from a source / sky above.
If one wanted to run a wire through the falling snow and make sure it didn't get wet or snow on it you could have the wire
inside of a round hollow metal tube.The tube "shields" what is inside from the outside and also keeps what's inside from
going outside the tube. No leaks inside or outside.
Not all shields are equal as some have just an open weave of stranded wire or another may have not only the wire
weave / briade but also a continous layer of metalic wrapped around the inside wires. Thus shielded wire can be water
proof or water resistant ...so to speak. Now note that what is inside can't mix with what is outside due to shielding,
but if you have naise on the wires to begin with and put them in a tube you will have that noise when the wire the wires exit.
In fact they may get the wires wet if it sticks or mixes with the insulation on the wires....coupling / mixing / etc ....
So a good quality 100% shielded wire of which the shield is connected back at the beginning of the run ( control box ) and
just left covering at the end ( stepper side ). The shield at the control box is connected to a EMI / RF / easy separate path ground
system which can go to earth ground. ie; You don't tie the shield to say a ground used for a circuit.
Now back at the control panel, should the outside conduit get wet, or the inside wire, the "water" will flow the easiest path to ground
via it's separate path.
Note that wires from the contoller provide a conductive pathe for a pulse stream to the steppers and is rather low in frequency or a single frequency. Noise is a group of frequencies which make no sense.
A pulse stream _-_-_-_- as compared to noise |||||||||||||||||||| which varing in intensity and frequency.
Said differently, the pulse stream may actualy make sense to ones hearing if put to a speaker where the noise signal would not be
understood by our hearing. Mix the two together together and you would have a poopy radio station that your trying to listen to
and you can't do anything sometimes to improve the radio reception.
One can envision the water in the inside tube as maybe being realy slow flowing, and we want to keep it that way,
while the water on the outside tube is fast movng and we do not want the fast and slow moving water to mix.
Thus we want to keep the signal path inside the shield from mixing with any other signals whereby they ( noise)
dosen't tag along or mix with signals of the inside wires.
A number of mixed analogies and hopefully you get the intent,
RICH
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