Earth ground for simple DC circuit

Discussion in 'The Projects Forum' started by Lightfire, May 1, 2011.

  1. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
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    Hello,

    (Look at my schematic, please)

    As you may notice, I only made a simple direct current circuit.:)Which is composed of a 12V battery and three 12V bulbs.

    Now, as you may see there, there's a symbol of ground there. Isn't it symbol of ground? If not, then let's say it's symbol of ground.

    Now, here's my question.

    1) Is it correct that I have put the ground on negative terminal of a battery?
    2) How's it working? I mean what's the essence of having that?

    Eh, what ground should I use for a simple DC circuit like this. The AC earth ground? Like this: http://en.wikipedia.org/wiki/File:HomeEarthRodAustralia1.jpg

    Or what?

    Thank you!:)
     
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  2. anselm

    New Member

    May 1, 2011
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    Do away with the extra "earth" symbol, the battery negative IS your ground.
     
  3. CDRIVE

    Senior Member

    Jul 1, 2008
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    Really? and you learned that where?
     
  4. Audioguru

    New Member

    Dec 20, 2007
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    A "ground" in a schematic is just a common reference that voltages are measured from, it is not earth.
    Frequently many "ground" symbols are used on a schematic so there are not "ground' wires going all over the place. All the "ground" symbols are connected together in a circuit but are not connected to earth.
     
  5. CDRIVE

    Senior Member

    Jul 1, 2008
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    Lightfire, you're working with low voltage, so ground is not a critical safety issue. It certainly won't hurt to have an earth ground connected to the negative line though. Negative is usually the choice for ground because it's generally accepted that hot is positive. Keep in mind that bi-polarity is found in many circuits, like dual polarity power supplies and Op-Amp circuits. Because of this either positive or negative can be at ground potential.
     
  6. BillB3857

    Senior Member

    Feb 28, 2009
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    A ground reference is also required by most simulation programs. Without it, simulations throw errors or simply refuse to run.
     
  7. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    I've always understood that symbol to be chassis.
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    Circuits without a metal chassis or with a plastic housing also use the ground symbols on their schematic so that there are not ground wires all over the place.
    An earth symbol has three prongs pinting down into the earth.
     
  9. Audioguru

    New Member

    Dec 20, 2007
    9,411
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    Circuits without a metal chassis or with a plastic housing also use the ground symbols on their schematic so that there are not ground wires all over the place.
    An earth symbol has three prongs pointing down into the earth.
     
  10. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    my exposure has the inverted xmas tree as meaning 'earth' ground.
     
  11. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
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    Yes, this was another of Lightfire's topics where we discussed this very issue.
    http://forum.allaboutcircuits.com/showthread.php?t=52178
     
    Last edited: May 1, 2011
  12. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    Okay guys. :)

    Can you give me a schematic for a simple dc circuit with a ground system? :D

    I just want to see how it works. :D (even though i can't)

    Thanks!!!
     
  13. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
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    The Pitchfork one is earth ground.
    The upside down tree one is common ground of a circuit.
    Open triangles are either analog or digital grounds.
     
  14. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
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    there you go, words in and it's a pitchfork. I've always viewed it as a distributed buss.

    If you look in as many references, you'll see as many claims. I'll be sticking with my version, thankyou.
     
  15. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
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    Just wait until you get into a system that has different symbols for "grounds" for "logic signal common", "power distribution common", and "earthing safety ground" A more proper term than "Ground" may be "COMMON", meaning the specific symbol is Common to all circuits using that particular symbol. As already stated, the symbol greatly reduces the complexity of the schematic by inferring points being connected together without having to show the actual wire on the schematic.
     
  16. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    Ground has several different meanings, all valid.

    When dealing with low voltage DC, the earth has nothing to do with it.

    When dealing with high voltage AC, there is almost always a ground, which at some point is connected to the earth.

    In your application, ground is the common point, where you put the negative lead of a voltmeter to measure the other voltages.
     
  17. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    as mentioned in many threads, 'Ground' is probably the most widely misused term. The question is, should we as techs perpetuate the myth. It may seem a mute point, but in the world of power and instrumentation, it's carefully calculated.

    'Common' is a generalized term that means what it says, that all points marked as such are interconnected. 'Ground' on the other hand, refers to the desired neutrallity between the circuit and the surrounding environment, which most importantly considers our safety being within that environment.

    I understand and tolerate the misuse of the term in common application, but when it comes down to applying power, there's no room for generalities.

    How valid is that?

    Your Electrical Code declares 'ground' to have a single meaning, as it should, to be positively and securely connected to a grounding electrode.

    Ground is nothing but, and for those that offer experience or education, get your terms straight
     
    Last edited: May 2, 2011
  18. CDRIVE

    Senior Member

    Jul 1, 2008
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    Wow! Who wudda thunk that this topic would trigger, what appears to be, combat readiness? :eek:
     
  19. Wendy

    Moderator

    Mar 24, 2008
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    Try looking it up elsewhere, the use is valid and appropriate. You may disagree with common usage, but you do not define it. No one person does.

    Common may be a better way to describe the common point in circuits, but the definition has gotten very ambiguous over time, and the symbol as I use it is definately used that way. When it comes to applying power with batteries, there are generalities. Electricians and electronics codes diverged quite some time ago.

    http://en.wikipedia.org/wiki/Ground_(electricity)

     
    Last edited: May 3, 2011
  20. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
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    In searching I've found that some authentic looking places say one thing and another will say the opposite:
    http://digital.ni.com/public.nsf/allkb/11BE00780D41622686256BE5006F04CF
    http://www.rapidtables.com/electric/electrical_symbols.htm

    In other words it's somewhat of a moot point, left to the knowledge of the circuit designer to use the symbols in a clear enough way that someone else can easily determine which symbol is intended to mean chassis or common ground and which symbol is intended to mean earth ground.
     
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