Unit 16: Systems and programming
LO3: Be able to program Programmable Logic
Controllers (PLCs)
Input and outputs, Boolean operations
Learner activity sheet
Activity 1
Ladder logic is a computer language that is commonly used to program the programmable logic
controller (PLC).
Ladder logic uses symbols to represent parts of the computer program.
Begin by identifying and describing the properties described by the ladder logic symbols shown below:
Symbol
Version 1
Description
Activity 2
Ladder logic programs can be created to perform Boolean operations (such as AND, OR, NOR etc.).
Look at the table below which shows some common logic diagrams representing Boolean operations.
Complete the table by filling in the truth table for each Boolean operation, and insert the appropriate
ladder logic equivalent diagram to perform this in ladder logic.
Logic Diagram/Boolean
Operation
A
B
Truth Table
Ladder Logic Equivalent Diagram
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
C
AND
A
B
C
OR
A
B
C
NAND
A
B
C
NOR
A
B
C
Exclusive OR
Version 1