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Automating Manufacturing Systems - Process Control and ...

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plc boolean - 6.21<br />

Inputs Output<br />

S M W A<br />

0<br />

0<br />

0<br />

0<br />

1<br />

1<br />

1<br />

1<br />

0<br />

0<br />

1<br />

1<br />

0<br />

0<br />

1<br />

1<br />

0<br />

1<br />

0<br />

1<br />

0<br />

1<br />

0<br />

1<br />

0<br />

0<br />

0<br />

0<br />

1<br />

0<br />

1<br />

1<br />

alarm off<br />

alarm on/no thief<br />

alarm on/thief detected<br />

note the binary sequence<br />

Figure 6.20<br />

Truth Table for the Alarm<br />

The Boolean equation in Figure 6.21 is written by examining the truth table in Figure<br />

6.20. There are three possible alarm conditions that can be represented by the conditions<br />

of all three inputs. For example take the last line in the truth table where when all<br />

three inputs are on the alarm should be one. This leads to the last term in the equation. The<br />

other two terms are developed the same way. After the equation has been written, it is simplified.

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