Avoiding newbie mistakes that causes noise

Other Hardware 3rd Party Boards
1

Hello,

I'm not an electrical engineer, so please go easy on me.

I need to make sure I "avoid" newbie noises in my Hardware. I understand that the arduino might be noise; but I just want to make sure I understand the general rule for properly grounding.

  1. My understanding is that is "recommended" to use shield cable if I want to connect an external Sensor and a Micro-controller. But what about the shield wire (or extra GND i call it):

  • Do I connect the shield metal wire (SGND) to the GND of the microcontroller? In this case, the Arduino Gnd?

  • I have seen PCBS that have a GND and SGND; How do I do make a SGND in the actual PCB?

  • If I use the diagram attached (simple temp sensor); where do you connect the SGND from the shield cable if I have a shield cable connected to the sensor?

  1. Should I enclose the PCB using Faraday Cage method? Ex. can I enclose the Arduino and this will help avoiding noises?

  2. If I'm using sensitive sensors; should I try to avoid using a Laptop? and instead use a PC?

I guess; i need basic tips that can make a big difference when starting to design a PCB from the beginning. Thanks for the help!

Arduino_circuit_07_01.png
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2

SGND should be common to all cable shields and metal enclosures in the system thus forming a Faraday cage. The Arduino Uno reference schematic shows a shield ground network for the USB shield. It's connected to the GND net via a ferrite inductor (low DC resistance, high(ish) AC impedance). SGND will probably be connected to earth ground via the host computer by way of the USB shield. In an isolated battery powered system, this isn't necessary.

For wiring to the sensor use a twisted pair for power + power return (GND). Use a separate twisted pair for signal + signal return (GND). "Power return" and "signal return" are common at both ends but the respective currents will tend to follow the paired wire.