Ground?

Discussion in 'The Projects Forum' started by Lightfire, Mar 29, 2011.

  1. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
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    Originally posted by SgtWookie at my earlier post.

    So, I really don't know what is ground or whatever. I got the feeling that the ground that most people are saying is the third wire. What is that? How to install that wire? It can be installed in battery? How?

    Thanks...
     
    Last edited: Dec 5, 2012
    SgtWookie likes this.
  2. GetDeviceInfo

    Senior Member

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    http://www.hark.com/clips/txctrbvdjh-thats-hilarious
     
  3. SgtWookie

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  4. studiot

    AAC Fanatic!

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    What is all this about?
     
  5. Lightfire

    Thread Starter Well-Known Member

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  6. SgtWookie

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    Our OP doesn't understand what "ground" is. Hopefully, the Wikipedia link that I posted will help to clear up their confusion.
     
  7. Lightfire

    Thread Starter Well-Known Member

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    but it can connect in simple dc circuit??? just project????
     
  8. SgtWookie

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    It could. Battery powered projects are usually "floating" - they have no electrical connection to earth ground. However, it is still common to declare one point of the circuit to be the 0v reference. In the case of a single-supply system, it is most frequently the negative side that is declared to be 0v, or the ground reference point.
     
  9. CDRIVE

    Senior Member

    Jul 1, 2008
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    After the OP reads those articles be prepared to answer the inevitable question regarding long running discrepancy of the Earth GND vs. Chassis GND symbol. I was taught using the convention that we use here on AAC and in all the Spice programs I've used. Over the years, most schematics have also followed this convention but there's always been the occasional exception. If I were to guess, I'd think that the most probable cause for the discrepancy was born between the electronics industry and the electrical (Electricians Union) industry but not sure. To further muddy the water, most circuits today don't employ a metal chassis. Here at AAC we're dealing with mostly with PCB design which (technically) should be drawn as an inverted triangle to indicate a Common Gnd, Board Gnd, System Gnd, Circuit Gnd, Floating Gnd and any other above ground terms I've missed. From an aesthetics point of view I've never liked it.

    There's yet another ground symbol that I use. See attachment.
    This is a classic "Bar Napkin Ground Symbol" that I like to call the "Lazy Z". :D
     
  10. Wendy

    Moderator

    Mar 24, 2008
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    I'd never seen the Lazy Z, I'll have to remember.

    Ground, as referenced to electronics only, is the common point. It is where you put the negative lead from your meter, and the other voltages are measure with the positive meter lead.

    Some circuits use more than one power supply. Op amps are the usual example, they use two voltages, a plus and a minus, and ground is where they connect. This is a bit advanced for you, but not too much so.

    My personal convention, where there is only one power supply (or battery), is that negative is always ground. This is pretty common, but not written in stone.

    There was a time with cars, many decades of years ago, that ground was the positive lead from the battery. This has pretty much gone away.
     
  11. studiot

    AAC Fanatic!

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    The difficulty with calling the chassis 'ground' is that it may not be.

    At one time many televisions and mains radio sets were build on metal chassis. Many parts of the circuit were connected to chassis, but the chassis was not earthed ( connected to the incoming mains earth ). Indeed in some models the chassis was live.

    Although this is no longer practiced, the symbol for connection still remains and some assemblies of industrial apparatus is built into a metal frame. Connections to such a frame is still correctly represented by this symbol.

    CDrive's lazy z usually represents mains ground.
     
  12. bertus

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  13. CDRIVE

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