Voting Circuit

Discussion in 'Homework Help' started by ckrupala, Oct 28, 2009.

  1. ckrupala

    Thread Starter New Member

    Oct 28, 2009
    2
    0
    For Digital Electronics I have been trying for hours to figure out a way to simplify this circuit:

    X=(STxV)+(PS+PT+PV)

    I have tested it in MultiSim and it works perfect.

    The scenario is that you have to make a voting machine so that the President's (P) vote counts as 2, and the Vice President's (V), the Secretary (S) and the Treasure (T) counts as 1.

    3 Votes are needed to pass and make X = 1

    The fun part is that it needs to be as efficient as possible by using only AND, OR, and NOT gates for a total of less than 8.

    I have tried all sorts of wacky things and have not yet figured this out.
    Any help or tips would be greatly appreciated.. :)

    I am using MultiSim 10.1
     
    Last edited: Oct 28, 2009
  2. jut

    Senior Member

    Aug 25, 2007
    224
    2
    So X is a boolean value? What does STxV, PS, PT, PV stand for, exactly?

    Post the schematic please.
     
  3. ckrupala

    Thread Starter New Member

    Oct 28, 2009
    2
    0
    X is the boolean value.

    Here is a truth table of the values that need to work.

    P V S T
    0 1 1 1 = 1
    1 1 1 1 = 1
    1 1 0 0 = 1
    1 0 1 0 = 1
    1 0 0 1 = 1
    1 1 1 0 = 1
    1 0 1 1 = 1

    Diagram of what I have now is attached.
     
  4. jut

    Senior Member

    Aug 25, 2007
    224
    2
    According to your truth table, no matter what the inputs are, the output is a 1. That can't be right.

    Are you guys studying Karnaugh maps?
     
    Last edited: Oct 28, 2009
  5. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    Not all possible input's were put in the table, just the ones where the output equals one.

    I think he forgot

    P V S T
    1 1 0 1 = 1
     
  6. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    Given you original equation:

    X=(STxV)+(PS+PT+PV) assuming it is X=((ST)V) + (PS+PT+PV)

    Is there anything common to the terms in the second half of your equation? If the President votes, what else needs to happen...
     
  7. RiJoRI

    Well-Known Member

    Aug 15, 2007
    536
    26
    "The fun part is that it needs to be as efficient as possible by using only AND, OR, and NOT gates for a total of less than 8."

    Check out the 74HC21 dual 4-input AND gate and the 74HC4075 triple 3-input OR gate. (Along with an inverter.) You should be able to solve X = (P' * V * S * T) + (P * (V+S+T)) readily, using only 4 gates.

    --Rich
    P.S. -- If V, S, & T are TRUE, then the state of P is immaterial. The solution becomes:

    X = (V*S*T) + (P * (V+S+T))
     
    Last edited: Oct 28, 2009
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