Midterm Examination. Practical Work.
Note: This is Written Practical Work with all answers and diagrams.
1. Give a full explanation of PLC. List its components and support your answer with
appropriate examples.
2. In the figure below, will the power for the output on the first rung normally be on or
off? Would the output on the second rung normally be on or off?
3. Draw a Ladder Diagram for the following case:
“The output switches on if Input 1 is on AND the other two are off, OR input 2 is on
AND the other two are off, OR input three is on AND the other two are off.”
4. a) Explain why a stop button must be normally closed and a start button must be
normally open.
b) Consider a case where an input to a PLC is a normally closed stop button. The
contact used in the ladder logic is normally open, as shown below. Why are they both
not the same? (i.e., NC or NO)
5. Simplify the following boolean equations.