# 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.

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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