Question about a certain schematic representation

Discussion in 'The Projects Forum' started by Kevin2341, Dec 5, 2013.

  1. Kevin2341

    Thread Starter Member

    Nov 1, 2009
    19
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    I'm in an freshman level EE class at the moment (circuit analysis to be exact), and we have to build a circuit of our choice from any schematic we can find (as long as it has a practical use, and not too simple like a 555 flasher).

    I found this schematic on Jameco,
    http://www.jameco.com/Jameco/Products/ProdDS/2169580Schematic.pdf

    I understand everything on this schematic except pins 3 and 4 on the 4017 chip. It shows a path going through this chip, and then those pins are highlighted in green but don't appear to be going anywhere, not even to ground.

    Can someone explain to me what this implies?
     
  2. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Just the way it's drawn so lines don't cross.

    3 goes to resistor.
    pin 4 to pin 15.

    vdd and vss not shown.
     
  3. Kevin2341

    Thread Starter Member

    Nov 1, 2009
    19
    0
    So I won't have to do anything with those pins then? The only pins I would use on the 4017 are 2, 13, 14, and 15?
     
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    You would use pins 2, 3, 4, 13, 14, and 15 plus 16 and 8 for power and ground.
     
  5. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    3 is used. connected to resistor ldr
    as is 8 an 16 not shown, to power counter
     
  6. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Ignore the meaning of lines drawn inside the chip. You will be wiring around the outside.

    Someone on here may volunteer a real drawing. :)
     
  7. Kevin2341

    Thread Starter Member

    Nov 1, 2009
    19
    0
    ok, so maybe someone can walk me through this. (or do a schematic redraw). I'll attempt to explain what I understand about this. I think I understand the lines now, but I want to get correction in case I am understanding this wrong.

    Going left to right on the schematic for 4017:

    Pin 14 connects to pin 6 of the opamp
    Pin 13 connects to ground
    Pin 15 Connects to the power supply (with a switch in it? Possibly an on\off switch?)
    Pin 3 is connected to pin 2 of the opamp with my LDR in between these two pins
    Pin 2 connects to the speaker
    Pin 4 connects to Pin 15 (which will connect through a switch to the power supply?)

    And then pin 8 and 16 will connect to the battery\power supply and ground? According to the pinout I'm reading from a google search, pin 8 is Vcc (positive voltage as I've known it?) and pin 16 is Vdd (ground?)

    Does this sound correct to you all?
     
  8. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    All correct, except I think the switch is a reset switch.
     
    Kevin2341 likes this.
  9. iimagine

    Active Member

    Dec 20, 2010
    129
    9
    Where there is a dot, there is a connection.
     
  10. Kevin2341

    Thread Starter Member

    Nov 1, 2009
    19
    0
    Oh yeah, you're right about that. Ok then, thanks for the help everyone, I think I should be able to put this together then :)
     
  11. tracecom

    AAC Fanatic!

    Apr 16, 2010
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