Chapter 11: PLC Compare Instructions Lab Activity

PLC Compare Instructions

• PLC compare instructions are used to compare values in a PLC program.
• There are five types of PLC compare instructions:
  • A. Equal to (EQU): compares two values to determine if they are equal.
  • B. Less than (LES): compares two values to determine if one is less than the other.
  • C. Greater than (GRT): compares two values to determine if one is greater than the other.
  • D. Less than or equal to (LEQ): compares two values to determine if one is less than or equal to the other.
  • E. Greater than or equal to (GEQ): compares two values to determine if one is greater than or equal to the other.

Lab Activity 11-2: LogixPro Lab

• The objective of the lab is to practice using compare instructions and to create a PLC ladder logic diagram using LogixPro simulation software.
• The lab consists of two activities:
  • Activity 1: Describing and practicing compare instructions.
  • Activity 2: Using compare instructions to compare the sum of two values.

Activity 1 Procedure

• Step 1: Describe the PLC compare instructions and provide an example for each.
• Step 2: Assign PLC input/output ports to devices.
• Step 3: Create the PLC ladder logic diagram using LogixPro simulation software.
• Step 4: Place the software in run mode and download the PLC ladder logic diagram.
• Step 5: Demonstrate the working PLC system to the instructor.

Activity 2 Procedure

• Program the PLC station using two counters to count the pressing of two pushbuttons.
• Use the ADD instruction to add the counter values together.
• If the sum is greater than 10, turn the green pilot light (Green_PLT) on.
• If the sum is less than 10, turn the red pilot light (Red_PLT) on.