Questions about schematic symbols

Discussion in 'Electronics Resources' started by Chris Wright, Nov 21, 2006.

  1. Chris Wright

    Thread Starter Well-Known Member

    Jul 26, 2006
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    A couple of questions about schematic symbols.

    1) The part C2 at "A" is a 10 microfarad Cap, but I'm not familiar with this symbol. Is it for a electrolytic cap? If so, is it polarity sensitive and what is the polarity, the thick side positive or no polarity?

    2) What value does "8K2" represent for the resistor at "B"? I've seen this notation a few times before, but I'm not familiar with it. Does the "K" take the place of the decimal point to avoid confusion? I.E. It is 8.2K as opposed to 82K

    3) At "C", is the value 100 nanofarads (or .1 microfarad)?

    [​IMG]
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    A) The symbol is for an electrolytic. The + is for the thick line inside the U shaped border.

    B) 8K2 is indeed 8.2K where the K shows the location of the decimal point.

    C) nano means 10e-9 and micro means 10e-6

    So
    Code ( (Unknown Language)):
    1.  
    2. 100e-9 = 0.1e-6
    3.  
     
  3. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    143
    I am stumped!

    Correct, the resistor is 8.2kOhms.

    100nF = 0.1uF

    Dave

    Edit: D'oh! Papabravo beat me to it!
     
  4. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
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    Don't you mean: nano means 1e-9 and micro means 1e-6?

    Dave
     
  5. Papabravo

    Expert

    Feb 24, 2006
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    Yes. I was thinking 10 to the minus nine and 10 to the minus six when I wrote the programmers shorthand for exponential notation. The digits before the "e" are mantissa digits not exponent digits. I should have written:

    10^-9 and 10^-6 since that was where my thought process was.
    I learned engineering in the days of the slide rule and we always wrote our answers as:

    6.02 * 10^24 instead of 6.02e24

    Sorry for the confusion
     
  6. Chris Wright

    Thread Starter Well-Known Member

    Jul 26, 2006
    62
    0
    Thanks to you both for the responses. I guess my assumptions were correct, ... but you know what happens when one assumes!

    Now that the Tryptophan is wearing off, I've been thumbing through the Jameco catalogue to put together the components for the above schematic, but I can never seem to exactly match the numbers.

    Now, I gather that there is some sort of "generic" numbering system for components? Where can I find a listing of these component "generic" numbers and a description of what they do? Or is there some sort of chart to decode them?

    For instance I know a 7805 is a 5v regulator (as a 7812 is a12v and a 7815 is a15v), but the schematic calls for a 78L05. Is there a significance to the "L" that I could find from a generic list?

    The catalogue lists:
    7805K TO-3/2 5v IA
    7805T TO-220/3 5v 1A
    78L5CZ TO-92 5v 100mA
    78L05ACM SOIC-8 5v 100mA
    78M05 TO-220/3 5v 500mA

    Of the two with the "L" in them, 78L05ACM is a surface mount (which I don't want to try yet), and the 78L5CZ. Can I assume the "0" in front of the "5" was just a place holder and was dropped, but now what is the significance of the "CZ". And Jameco doesn't give the manufacturer to look up the manufacturer's data sheet.
     
  7. pebe

    AAC Fanatic!

    Oct 11, 2004
    628
    3
    The 'L' is for low power - 100mA max current as against 1A max for the 7805.
     
  8. Chris Wright

    Thread Starter Well-Known Member

    Jul 26, 2006
    62
    0
    This is what I had assumed, and thanks for confirming it. But the real question is:

    Where can I find the "generic" list so that I can decode the rest of the numbers now and in the future?
     
  9. Papabravo

    Expert

    Feb 24, 2006
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    Every manufacturer has different prefixes, infixes , and suffixes. There really is no standard and you need to add all manner of surface mount devices to the mix. For each manufacturer you need to look for "ordering information" which tells you how to decode their part numbers. It also happens, especially on newer parts, that the data sheet will be out of date.
     
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