(my) confusion about Vss and Vdd

Discussion in 'General Electronics Chat' started by sureshparanjape, Dec 23, 2014.

  1. sureshparanjape

    Thread Starter Member

    Feb 10, 2012
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    Recently I downloaded a data sheet, which gave pin lay out as given in attachment. I want to connect four NAND gates to get 2 to 4 decoder.I wish to connect, on breadboard, the four NAND gates to get the decoder. I notice in pin lay out Vss at pin 7 and Vdd at pin 14. I wish to use Arduino board to power and experiment. I got following questions:
    1.Do I connect 5V Arduino pin to pin 7 of IC?
    2.What do I connect to Vdd? GND?
    3. Can I connect the circuit without using E part in the figure?( file attached)
    I have written a sketch to get physical verification of the decoder using leds but can't try out unless I get the circuit right.
    Needless to say it just for experimentation.
    I have attached a file which gives two pictures- one for constructing decoder and another the pin layout.
    I would be thankful o those who would spend ime to answer my elementary questions.
    sureshparanjape
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Vss, pin-7, is connected to GND.
    Vdd, pin-14, is connected to 5V.

    Connect unused INPUTS to GND.
     
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  3. MaxHeadRoom

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    I prefer to use Power Common instead of GND, GND is too ambiguous, in N.A. it also refers to Earth conductor. ;)
    Max.
     
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  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    But the reality is that the zero Volt node in billions of schematics and PCB layouts has been labeled Gnd forever. Changing that now is like tilting at windmills...

    It would be easier to convince folks to call the other thing Earth, which is really what it is...
     
  5. MaxHeadRoom

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    Old Habits die hard.:p
    Max.
     
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  6. ErnieM

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    Apr 24, 2011
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    1.Do I connect 5V Arduino pin to pin 7 of IC?
    2.What do I connect to Vdd? GND?

    Oops, heck no, that is backwards.
    Vdd, pin 14 goes to the 5V.
    Vss, pin 7, goes to ground.

    3. Can I connect the circuit without using E part in the figure?( file attached)
    "E" seems to be an enable line. As long as your circuit works without an enable then yes you can just delete that line and use the 2-input NAND gates you have.
    (I do wonder where you get the invters from.)

    I have written a sketch to get physical verification of the decoder using leds but can't try out unless I get the circuit right.
    Needless to say it just for experimentation.

    An excellent way to learn!

    Generally a voltage pin with double letters (Vdd, Vss, Vcc and the like) mean a power rail. A single letter (Va, Vo, Vb) mean some signal voltage between the power rails.

    Vdd generally means the Drain supply on CMOS circuits (positive power).
    Vss generally means the Source supply on CMOS circuits (ground common).
    Vcc generally means the collector supply on transistor (TTL) circuits (positive power).

    And at the risk of further going off topic, the NEC (the electrical "code") refers to the safety potentian under the heading of "bonding" to avoid the "G" word entirely.

    To sureshparanjape: don't connect your circuit to anything on the AC power, that is a different "ground".
     
  7. MaxHeadRoom

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    This also gets into the area covered by NFPA79 Electrical Standards for Industrial Machinery.
    Bonding and Equi-potential bonding is another allied subject.

    NFPA 70 (N.E.C.):
    Grounded: Connected to Earth ground or to some conducting body that serves in place of Earth ground.
    Grounded Conductor: A System or Circuit conductor that is Intentionally Grounded or the grounded circuit of a wiring system to a grounding electrode.
    Max.
     
  8. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    ha ha ha... and #12 called me obtuse for my heat transfer observation on a previous thread... :rolleyes:
     
  9. sureshparanjape

    Thread Starter Member

    Feb 10, 2012
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    Many Thanks for nice explanation.
    As for your comment-"(I do wonder where you get the invters from.)", while searching for explanation of internet I came across informations like-
    "Vdd= 'Voltage Drain Drain'
    Vss='Voltage Source Source' "
    and concluded that source would be powr source and drain as another word for GND( what does GND do-drain all energy to ground!); Hence this (my)confusion!!
    Thanks for the last advice!
    Also many thanks to others for their nice gesture of giving helping hand.
    sureshparanjape
     
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  10. ErnieM

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    Apr 24, 2011
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    "Ground" means many things depending on context. Here ground just means all the wires and such connected to the negative side of the power source.

    So it is just a connection point.
     
  11. MaxHeadRoom

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    Where is 'Here' ? This OP or the AAC forum in general? as I see AC power questions here as well as electronic circuitry?
    Max.
     
  12. WBahn

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    Mar 31, 2012
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    Since the comment was made as part of noting that the term needs to be interpreted within the context in which it is used, it would seem most reasonable that the context in question is the one in which it was used by the OP.
     
  13. MaxHeadRoom

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    I'll take it under advisement. o_O
    Max.
     
  14. ErnieM

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    Apr 24, 2011
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    Max: my comment was in answer to the original poster.

    I am fairly certain he knows where "here" is without splitting hairs.
     
  15. WBahn

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    Well, then why just limit the options to the OP or the AAC forum? Perhaps "here" is the internet as a whole?
     
  16. sureshparanjape

    Thread Starter Member

    Feb 10, 2012
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    Thanks to all useful comments again. I could connect 4 NAND gates as 2 to 4 decoder and successfully checked the output on breadboard!
    sureshparanjape
     
  17. WBahn

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    How did you connect them?
     
  18. DNA Robotics

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    Jun 13, 2014
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    In the 1950’s and 60’s an Englishman named Lucas decided that the positive battery terminal on cars was ground.
    I think he discovered “Magic Smoke”.
     
  19. WBahn

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    Why? Lots of cars (and other systems) have used a positive ground convention.
     
  20. cmartinez

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    This is getting interesting... do you know of any specific case in the "other systems" category that has done this? Also, is there a specific reason why this could be an advantage over the standard negative ground?
     
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