Undergraduate Lab in Ladder Logic using the Rockwell Workstations

Undergraduate Lab in Ladder Logic using the Rockwell WorkstationsIntroduction to Basics and Lab EquipmentThe students will become familiar with the PLC (Programmable Logic Controller) , Rockwell Automation Workstation, and their purpose in Industrial Automation.

The lab will introduce the basics of Relay Ladder Logic and how it can be used in industrial automation applications.In the United States, ladder logic is the most popular method used to program a PLC

The students will be introduced to utilizing RSLogix5000 to implement the Ladder Logic programs and load them into the PLC For the past decades, programmable logic controllers (PLCs) using relay ladder logic (RLL) programming have been the workhorse for controlling event-driven industrial automated systems. RLL proved flexible compared to the hardwired RLL control implementation, due to its feature of software implementation. As automated systems become more complex, they also become more difficult to understand and maintain. It takes tremendous effort to accommodate specification changes, which become frequent, to meet todays flexible and agile automation needs.

Ethernet based AC drive speed controlHardware Connection Diagram

PowerFlex 40P 192.168.1.5

DC Input/Output192.168.1.7

192.168.1.101

I/O BoxAnatomy of Ladder LogicInput Instructions (conditions)Output Instructions (actions)Rung 0Rung 1Rung 2Left Power RailRight Power RailLogical Continuity Input Instructions (conditions)Output Instructions (actions)Rung 0Rung 1Rung 2TTFFFTTTTRung FalseRung FalseRung TrueANDed InstructionsORed InstructionsLeft Power RailRight Power RailExample Experiment 1: Motor ControlA practical application of relay logic is in control systems where we want to ensure two incompatible events cannot occur at the same time. An example of this is in reversible motor control, where two motor contactors are wired to switch polarity/phase sequence to an electric motor, and it is necessary to insure that the forward and reverse contactors are not energized simultaneously.Example Experiment 1: Motor Control Circuit 1

Figure 1 shows a control where the motor will stay energized after the button is pressed but will only stop when there is no more power availableFigure 1Example Experiment: Motor Control Circuit 1 Ladder Logic

Example Experiment: Motor Control Circuit 2

Figure 2In Figure 2 a stop switch has been added in which will allow the user to stop the motor when desired.Example Experiment: Motor Control Circuit 2 Ladder Logic

Full View of Example Ladder Logic Circuit in RSLogix 5000

ReferencesAllen-Bradley Logix5000 Controllers, Quick Start, User Manual Lessons In Electric Circuits, Volume IV Digital ,Tony R. KuphaldtPLC Fundamentals-Ladder Logic Fundamentals, Controls & Instrumentation for Automation, T.E. KostekA comparison of relay ladder logic programming and Petri net approach for sequential industrial control systems, Proceedings of International Conference on Control Applications, MengChu Zhou, E. Twiss