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Proper use of shielded cabling

Former Member

I have a project where I need to setup a handful of hall effect sensors and take measurements approx. 6' away from my Arduino microcontroller.  The sensor has 3 pins, PWR, GND, SIG.  For the longer distance run a friend recommended that I use shielded cabling.  My my question is how exactly do I hook this up?  Do I go with a 2 core shielded cable; 1 core for PWR, 1 core for SIG, and hook the sensor's GND pin to the shielding (or drain wire) -- and then tie the shielding to GRD at the Arduino, OR do I use 3 core cable so that I have 1 core to PWR, 1 core to SIG, and 1 core to sensor GND (as I would normally do) and then tie the cable shield (or drain wire) to the Arduino's GND as well???  I just want to be sure I have a good mental pictures of how things will get hooked up before I purchase shielded cabling.  Thanks in advance for any insight!

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    Brandon

    Generally shield cable is used to provide a ground over the data carrying conductors.

     

    If you are passing next to electrically noisy cables, the proper method is to ground (earth ground) the shield and connect the power, data and ground wires to the Arduino.

    Since the one wire sensor is not connected to a second ground, you are not likely to get earth loops, so you could use the shield as the ground and be quite safe.

     

    A six feet you should have no issues no matter what you use.

    You could always use cat5 cable and choose the data and earth as the pair that are twisted.

     

     

    You might have capacitance and loading issues as found here.

    Pas Home / Final fix for my 1wire temperature network

     

    His solution was to reduce the 4k7 pullup resistor from power to data to 1k5 with the results shown here

    Pas Home / Final Summary

     

     

    Mark

  • 0 in reply to mcb1

    Hi Mark,

     

    Thanks for the thoughtful response...it is tremendously helpful.  I am glad to hear that the configuration might be pretty forgiving at 6'.  Just so I am clear on your recommendation.

     

    You suggest that I could run 3 conductor cable from the Arduino to the sensor to handle PWR, GND, and SIG and then ALSO establish an earth ground to the shield (so essentially I need to make 4 separate connections; 3 to the Arduino and 1 to the earth ground).

     

    Is there any value in running 2 conductor cable to handle PWR and SIG and then tie the sensor GND to the shield and the shield to Arduino's GND?  This wouldn't establish an earth ground since I would be using the Arduino's GND and only saves me the hassel of running 2- vs. 3-conductor cabling...not much of a difference???

     

    Perhaps a better question is if I were to not bother grounding the shield at all would you expect problems with a 6' run???

     

    Thanks again for your help.  Very much appreciated!

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  • 0 in reply to mcb1

    Hi Mark,

     

    Thanks for the thoughtful response...it is tremendously helpful.  I am glad to hear that the configuration might be pretty forgiving at 6'.  Just so I am clear on your recommendation.

     

    You suggest that I could run 3 conductor cable from the Arduino to the sensor to handle PWR, GND, and SIG and then ALSO establish an earth ground to the shield (so essentially I need to make 4 separate connections; 3 to the Arduino and 1 to the earth ground).

     

    Is there any value in running 2 conductor cable to handle PWR and SIG and then tie the sensor GND to the shield and the shield to Arduino's GND?  This wouldn't establish an earth ground since I would be using the Arduino's GND and only saves me the hassel of running 2- vs. 3-conductor cabling...not much of a difference???

     

    Perhaps a better question is if I were to not bother grounding the shield at all would you expect problems with a 6' run???

     

    Thanks again for your help.  Very much appreciated!

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  • 0 in reply to Former Member

    Brandon

    2 conductor cable to handle PWR and SIG and then tie the sensor GND to the shield and the shield to Arduino's GND

    This would work.


     

    if I were to not bother grounding the shield at all would you expect problems with a 6' run???

     

    You do need to ground the shield otherwise it acts as a large antenna, and depending on its length, can introduce all sorts of frequencies.



    It's always difficult to predict what will happen, when you only have part of the information.

    If you run the cable next to other cables that are carrying digital signals, or carrying large currents, then its possible that some signal may be induced which could affect the performance.


    Any cable carrying current tends to produce a magnetic field whose sole purpose in life is to go forth and spread or induce others.

    The more current and or the closer the cable the larger induction.

    The lower the ratio between the signal you want, and the induced signal, the more likely your data will be corrupted.


    You could try the twisted cable as well, and you may find it works just fine.

    Mark

  • 0 in reply to Former Member

    You're welcome.

     

    Good luck, do let us know how you get on.

     

    Mark