Automating Manufacturing Systems - Process Control and ...

plc karnaugh - 7.3
expression.
The patterns can then be converted into a Boolean equation. This is done by first
observing that all of the patterns sit in the third row, therefore the expression will be
ANDed with SQ. Next there are two patterns in the second row, one has M as the common
term, the second has W as the common term. These can now be combined into the equation.
Finally the equation is converted to ladder logic.
Step 4: Look for patterns in the map
S Q
SQ
SQ
SQ
M W MW MW MW
1 1 1
Step 5: Write the equation using the patterns
Misthecommonterm
all are in row SQ
W is the common term
A = S ⋅Q ⋅( M+
W)
Step 6: Convert the equation into ladder logic
M S Q A
W
Figure 7.3
Recognition of the Boolean Equation from the Karnaugh Map
Karnaugh maps are an alternative method to simplifying equations with Boolean
algebra. It is well suited to visual learners, and is an excellent way to verify Boolean algebra
calculations. The example shown was for four variables, thus giving two variables for
the rows and two variables for the columns. More variables can also be used. If there were
five input variables there could be three variables used for the rows or columns with the
pattern 000, 001, 011, 010, 110, 111, 101, 100. If there is more than one output, a Karnaugh
map is needed for each output.