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Error in Schematics or am I missing something?

Discussion in 'General Electronics Discussion' started by JohnS0N, Dec 19, 2016.

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  1. JohnS0N

    JohnS0N

    12
    1
    Nov 14, 2016
    I am learning electronics by the book Make Electronics from Charles Platt. It is the second edition.

    And I am in experiment #8. I got it working, however I can not seem to grasp this picture.

    The author says that the right schematics picture corresponds to the simplified drawing on the left. However on the breadboard drawing the positive charge is connected to the 3rd pin on the relay (from up to down), while on the schematics it shows it should connect to the 2nd pin.

    Is that a book errata or am I missing something?

    Thanks a lot for looking!
     

    Attached Files:

  2. hevans1944

    hevans1944 Hop - AC8NS

    4,325
    2,031
    Jun 21, 2012
    If the intent is to alternately light the LEDs when the push-button switch is actuated and released, then the schematic is wrong. The positive from the battery must connect to the moving contact of the relay, which is pin 5. The anode of the left-side LED on the schematic must connect to the normally-closed contact, which is pin 3. The breadboard drawing is correct.

    BTW, dual in-line package (DIP) pins are numbered counter-clockwise starting at pin 1 in the upper left corner, continuing down to pin 8 in the lower left, then continuing from pin 9 in the lower right and back up the right side to pin 16 in the upper right... all this looking down on the relay package from the top (relay pins pointing down into the breadboard. There is usually a dot or a "U"-shaped notch on the package to identify which end to start the pin numbering from. Same pin numbering scheme applies to any size DIP package... 4-pin, 6-pin, 8-pin, 14-pin, 16-pin... etc. It gets really hard to count when the pins number twenty or more.:D Gets even worse when the package is surface mount and contacts are on all four edges. Becomes impossible when the package is a ball-grid array with contacts on the bottom. But you aren't there yet, so don't worry 'bout it.
     
    Last edited: Dec 19, 2016
  3. JohnS0N

    JohnS0N

    12
    1
    Nov 14, 2016
    Thanks so much hevans1944! I'm looking forward to much more confusion in the future :D

    In essence, just to be sure as I really want to understand it... we can conclude that the drawing and schematics do not represent the same circuit, as they should? The are different from each other, right? And thus, this is a book errata?
     
  4. hevans1944

    hevans1944 Hop - AC8NS

    4,325
    2,031
    Jun 21, 2012
    Yes.
     
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