Good Practice in soldering and pin connections

Discussion in 'General Electronics Chat' started by Šamaš-šum-ûkīn, Oct 16, 2014.

  1. Šamaš-šum-ûkīn

    Thread Starter New Member

    Oct 10, 2014
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    Hello,
    this is more about a confirmation than anything else (or correction if wrong).

    When we have a peripheral connector with unused pins, the good practice is to connect the unused pins to a GND, right? To avoid logical level flicking because of the surrounding noises...? How critical are the those flickers to pins that aren't even used?

    Just curious.

    Regards,
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Connect unused inputs only, not unused outputs.

    Whether you connect to Vcc or GND depends on the function of the input pin.
     
  3. ISB123

    Well-Known Member

    May 21, 2014
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    Solder a pull-up/down resistor.
     
  4. Šamaš-šum-ûkīn

    Thread Starter New Member

    Oct 10, 2014
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    My favorite question: Why? Why stabilizing the logical level of inputs only? What happens if we don't do that? I know this might be a very basic question, but I've just entered into the world of electronics. :)
     
  5. ISB123

    Well-Known Member

    May 21, 2014
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    The pin will act as an antenna and it can introduce EMI in your signals.
     
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    The answer is maybe or depends on the specific details/functions/requirements of that product..
    I'll tell you that I don't ever have any unused pins on "peripheral connectors" (chips/ICs yes and I follow the recommended practice in the datasheet)..
    The extra/unused pins in a connector simply cost money..
    If its unused.. why even have it in the first place.
     
  7. MrChips

    Moderator

    Oct 2, 2009
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    Are you referring to input pins on an IC or pins on a connector that are N/C (not connected)?
     
  8. Šamaš-šum-ûkīn

    Thread Starter New Member

    Oct 10, 2014
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    Nice answer from both of you. I see the chosen design is already a bad practice given the partial use of peripheral connectors. Also, now I understand the idea of parasitic EMI; every signal affects the other. Flickering signals that are too close will affect the precision or proper working of other neighbouring signals.

    Case closed. ;)
     
  9. Šamaš-šum-ûkīn

    Thread Starter New Member

    Oct 10, 2014
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    In fact, the peripheral connectors (if the name was correctly used) I am referring to are like this: [​IMG]
    From one PCB board to another with a multi-wire bus male connector.
     
  10. MrChips

    Moderator

    Oct 2, 2009
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    It depends on what is connected to the pin.

    I would say leave the pin alone - don't connect anything unless you are told to connect to something.
     
  11. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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    Usually you attach to whatever results with the lowest power dissipation.
     
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