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  1. #1
    Wiring limit switches using 2 core shielded cable. 1st wire from farthest switch back to board, 2nd wire daisy chained through all other switches and back to board ... the shielding ... one end to my central grounding point ... My question is what do I do with the other end? Attach a cable and run it back to the ground point? Leave it alone? what?

    Sorry about the question ... electrics are not my strong point.
    Tim G-C

    I disapprove of what you say, but I will defend to the death your right to say it.

    (attrib. Voltaire but written by Evelyn Beatrice Hall "The Friends of Voltaire" 1906)

  2. #2
    i2i's Avatar
    Lives in Cardiff, United Kingdom. Last Activity: 23-12-2016 Has been a member for 7-8 years. Has a total post count of 693. Received thanks 30 times, giving thanks to others 0 times.
    leave it alone, but heatshrink the end to stop it shorting on anything

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  4. #3
    Cheers ... I hoped someone would say that ...

    Much appreciated
    Tim G-C

    I disapprove of what you say, but I will defend to the death your right to say it.

    (attrib. Voltaire but written by Evelyn Beatrice Hall "The Friends of Voltaire" 1906)

  5. #4
    Tim

    Second wire should finish at last switch and i would bond the shield to a common earth (not the negative)
    If the nagging gets really bad......Get a bigger shed:naughty:

  6. #5
    Silly question ... I was wondering if running UN shielded cables through the central core of aluminium extrusion would work as well as using shielded cable outside??? I mean its surrounded by metal (I'm using shielded by the way) I'd just thought I'd ask anyway ...
    Tim G-C

    I disapprove of what you say, but I will defend to the death your right to say it.

    (attrib. Voltaire but written by Evelyn Beatrice Hall "The Friends of Voltaire" 1906)

  7. #6
    Tim

    This can work but you can pick up stray signals at the end of the cables as well as the middle, always a suck and see with that type of thing.
    If the nagging gets really bad......Get a bigger shed:naughty:

  8. #7
    i2i's Avatar
    Lives in Cardiff, United Kingdom. Last Activity: 23-12-2016 Has been a member for 7-8 years. Has a total post count of 693. Received thanks 30 times, giving thanks to others 0 times.
    what you must consider is the interference between the cables running inside the extrusion.

  9. #8
    Be careful of old man Eddy
    If the nagging gets really bad......Get a bigger shed:naughty:

  10. #9
    I agree, leave the other end disconnected to avoid a ground loop.

    Lets us pretend that the interference is actually a snowstorm containing various electromagnetic waves, from motors, radio, TV, sparks, transformer, random noise etc. Your shield, or coat in this analogy, is some sort of metal shroud that creates a low resistance path to ground. It should stop the snow from getting in, or out however this depends on the type/size of snow and coat. If the shield is completely closed then not much is going to affect it, however if there are holes in the shield, such as in an open braid it's different. These holes are effectively closed if the snow is too big (the source of interference has a long wavelength) and vice versa.[It'd be interesting to compare this with the frequency stepper driver uses.] Snow settling on you whilst walking outside probably wont bother you, however if you never wipe it off or it doesn't melt then it could impede your walking. However if your coat allows the snow to slide off easily to ground then there's no problem. If you walked under a tree and a significant amount of snow fell on you (motor switched on causing lots of noise) then you fall over (signal disrupted). With the stepper motors it's not so bad, since you're walking back and fourth with the snow falling evenly (wires are all the same length (resistance), and common ground), so no snow will accumulate and prevent the small amount of snow (background noise/interference) being conducted to ground. So there's no ground loop...

    Hopefully that helps.

    With regards to aluminium extrusion, I think that seems reasonable as long as you don't put multiple wires down the hole since that might induce crosstalk (snow falling off you onto someone else!).
    Last edited by Jonathan; 29-10-2010 at 12:36 AM.

  11. #10
    Jonathan

    Thats a great explanation
    If the nagging gets really bad......Get a bigger shed:naughty:

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