Controversial schematic symbol

Discussion in 'General Electronics Discussion' started by tedstruk, Jul 11, 2018.

  1. tedstruk

    tedstruk

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    Now here I go again.
    The capacitor symbol is a widely used and important part of the diagram. It consists of a bar seperate from another bar, and often has (the following is as I learned it DIY study and research); A straight bar, with a curved bar on the opposing side.

    A barred line on schematics usually represents a block such as a diodes direction where the arrow designates the signal , or flow. but the way I learned it was that there is one exception to the rule, and that is the capacitor. In that case, it represents a cell terminal in a multi-cell battery(a type of capacitor), or a terminal on the positive side of the circuit and the curved line representing the negative side of the circuit.

    NOW there are lots of symbols for capacitors! two straight bars, the straight bar and curved bar, the straight and curved bar with a + sign on it, and of course the multiple, two sized straight bar symbol, indicating the cells in the battery.

    Usually....(in my opinion..not so good!)
    The cap is installed with the straight bar toward the flow, kind of like a stopper that has to charge, before it fires.
    and that means the curved line goes toward the grounded or
    "where the -(negative) side of the capacitor connects".ie. an antiquated polarized electrolytic type

    Now the teaching of the schematic symbol art is lost in all home made circuits and they are fading fast.

    I have a set of 0.1uf caps in my schematic. They are both straight bars with curved bars, but no + sign on them.
    Am I to presume that the straight bar is the + positive connection of the capacitor, and curved bar the - negative ?

    Or am I to assume that in power electronics, this is moot, arbitrary, and not warrenting any further discussion?

    I am asking this because I have run into this same misnomer every time I build something electronic. and it bothers me everytime....

    When I trust myself, it usually works. when I trust the taught diagramatic symbology of the electronical sciences, it fails.
    IDEAL? man I didn't even get past batteries and capacitors yet!

    how, can this be fixed so that our best techs don't blow the caps up in their faces?
     
    tedstruk, Jul 11, 2018
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  2. tedstruk

    Minder

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    I believe what you are referring to is non-polarized capacitors, IOW they work with both polarity.
    One of the main reasons for this difference in marking is in HF or radio circuitry where the capacitors are use for de-coupling.
    The curved bar end goes to ground connection, this connects to the outer foil of the cap, this ensures that the outer foil of the cap is also close to the ground connection in a capacitive sense.
    In many simple LF or slower digital circuitry, it is not so important.
    M..
     
    Minder, Jul 11, 2018
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  3. tedstruk

    kellys_eye

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    Electronic schematic symbols follow one of three standards:

    IEC (British)
    ANSI
    IEEE (American)

    and whilst there are similarities between some, there are also some (glaring?) differences too. Ideally, any schematic is drawn using ONE standard (try not to mix standards!) and the symbols readily available from the 'standards site'.
     
    kellys_eye, Jul 11, 2018
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  4. tedstruk

    Minder

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    Pretty much the same as the use of the Ground/Earth/Chassis/Logic common symbols.
    Very Rare to see the correct one used.:(
    M.
     
    Minder, Jul 11, 2018
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