Grounding in electronics question

Discussion in 'General Electronics Chat' started by Leonard Cua, Aug 4, 2015.

  1. Leonard Cua

    Thread Starter New Member

    Aug 4, 2015
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    Hello to all! I am very new to electronics and I have some questions regarding ground in electronics. I understand that there are 3 types of grounds used in electronics Signal, Chassis and Earth. I am confused as to how I should wire it when I encounter it in different schematic diagrams. Thank you in advance and hope someone could help a newbie like me.

    Are all of these types of ground connected the same way like the illustration with earth ground below or is signal and chassis ground different?

    [​IMG]
     
  2. DickCappels

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    Aug 21, 2008
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    [​IMG]
    In general, all points indicated to be "ground" with a given symbol should connected to one-another. Sometimes there are many signal grounds that need to be kept separate to avoid cross-talk and noise and they usually but not always meet one-another somewhere.
     
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  3. #12

    Expert

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    The one on the right is especially convenient when you have more than one circuit, but they are not connected, as when an opto-isolator is used or a transformer has more than one secondary winding, because you can put a symbol in the triangle, like, "A" or "B" or "1" or "2".
     
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  4. Leonard Cua

    Thread Starter New Member

    Aug 4, 2015
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    Thank Dick and #12! So does this mean that all types of ground are wired the same way in electronics (you connect all the ground together with the exception if there symbols inside the triangle) and that the reason for making different kinds of symbol for ground is because of their purpose?
     
  5. #12

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    Connect all similar ground symbols, each in their own group.
    It's normal to have one Earth ground, one chassis ground, and a bunch of circuit ground symbols.
    That's 3 types. They do not get connected together unless you know exactly why and where to mix them.
    That is not covered in the first chapter, so to speak.
     
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  6. DickCappels

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    Aug 21, 2008
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    Just to expand on that a little bit, when connecting grounds of a given symbol it is often necessary to pay attention to the path that the ground follows through the circuitry, for example having several amps of current go through the ground traces in a sensitive circuit would result in an IR voltage drop along the ground path that could cause significant errors in the output of the circuit.

    This sort of "ground loop" problems is more significant as frequency increases and rise & fall times get shorter.

    "War" story: I once made a 5 amp linear power supply (state of the art in those days -2N3055 output and all that!) but because of careless grounding as I increased the load on the power supply, the output voltage went UP rather than more logically sagging or staying stable.
     
  7. Jony130

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  8. MaxHeadRoom

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    Jul 18, 2013
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    As I have pointed out more than once, there can be some confusion because often many examples and literature shows the earth ground symbol used indiscriminately in various circuits to indicate power common whether the circuit is earthed or not.
    The starting point is as in post #2.
    In electronic systems that mate one or more separate systems together, there are often two schools of thought, one is to isolate each system power commons from any other, the second (which I mainly subscribe to) is to bond all commons where possible and bond this to the a service earth ground, usually in what is known as a Star Ground earth.
    http://sites.ieee.org/ctx-emcs/files/2010/09/Archambeault-Ground-Myth.pdf
    http://www.automation.siemens.com/doconweb/pdf/840C_1101_E/emv_r.pdf?p=1.
    Max.
     
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  9. dl324

    Distinguished Member

    Mar 30, 2015
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    I agree with this somewhat...

    When I was learning electronics in the 70's, I was taught to use the leftmost symbol in post #2 as circuit ground. In drafting, we were taught the number of lines to use. For fun, I leafed through a half dozen texts and databooks I have from that era and all of them used the "earth ground" symbol for circuit ground. I didn't start seeing the rightmost ground symbol until later and I always considered it to be "style" (much like some draw resistors as rectangular boxes and some draw them with an asymmetrical number of "humps"). I didn't start using the triangle ground symbol until I started using a schematic editor about a decade ago. When I hand draw I'm more inclined to use what I was taught...
     
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  10. MaxHeadRoom

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    My teachings were in the UK and tube era and I grew up with schematics such as below.
    Also earth ground is called Earth unlike N.A. where the term ground is used for power common And earth.

    I see schematics posted here frequently where the earth symbol is used an it is not clear whether the poster intends it to be earth ground, isolated or?
    Max.


    [​IMG]

    [​IMG]
     
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  11. PeterCoxSmith

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    Feb 23, 2015
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    Functions of different kinds of ground are different.

    Earth is a connection to mother earth and comes into your circuit via the mains connection and it will be used for safety to prevent electrocution; no current should flow in any earth connection except under fault conditions which will trip a circuit breaker or a fuse.

    Chassis is the metal work of your electronic package and again it is most likely connected to earth for safety; no current should flow through the chassis but it may be used for the EMC filters to direct noise away from your circuit and back to the mains source.

    Circuit ground which is the 0V of your circuit supply will carry the return current to your supply; the trick in electronics is to use a star point for 0V so that it can be used for current return and for a circuit reference point, which should not have current flowing through it.

    In a circuit digram and for simulation a ground symbol is used to save putting in many lines that would clutter the drawing. For all normal simple circuits use the circuit ground symbol and only use chassis for connection to the metal work of your system and use earth for the incoming mains.

    well that's my advice...Peter
     
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  12. #12

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    I bet you forgot how to do that by now. :D

    I have used a few megs of positive feedback resistor on the voltage divider (which makes the reference voltage) to obtain incredible stability, like 28.000 volts to 28.008 volts from zero load to full load (4 amps). The delta Vbe of a 2N3055 is used to increase the reference voltage during load conditions. Of course, the gain of a 2N3055 is so different from one transistor to another transistor that the amount of resistance is always a custom select. In practical terms, this is probably not. It was just a curiosity I indulged myself one rainy afternoon.
     
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