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Homework Help: Boolean Logic design help

  1. Mar 25, 2010 #1
    1. The problem statement, all variables and given/known data

    Using NAND, AND OR, &/or NOR gates build a vote counting machine. It should light an LED when majority votes are true (or answer "yes"). Assume 4 input votes only.


    2. Relevant equations

    Boolean Logic

    3. The attempt at a solution

    So I know the solution in terms of algebra, which is ABC + ABD + ACD + BCD (where ABCD are the 4 input votes) and I know at the end I need two OR gates summing up to one single OR gate. Not sure how to design the beginning though.

    I am also looking for a way to simplify it since I have to build the whole thing out of NAND gates only.
     
  2. jcsd
  3. Mar 25, 2010 #2

    berkeman

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    Staff: Mentor

    Your problem statement doesn't confine you to 2-input gates. It only takes two levels of logic to do it with AND-OR logic, right?

    Are you constrained to only using 2-input NANDs for the final circuit? How do you make an OR out of a NAND? Have you looked at the inverted function in case it offers some optimization? Please show us more work...
     
  4. Mar 28, 2010 #3
    Yeah we can have 4 inputs, but I am still not sure about you saying using the two level AND-OR logic.
    I know how to construct the different kind of gates from NAND gates now, just need a clear concept how to solve this problem.
     
  5. Mar 29, 2010 #4

    berkeman

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    Staff: Mentor

    Show us your initial truth table and initial logic implementation.
     
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