How to Program an Omron PLCby John Yarbrough
The programmable logic controller (PLC) is crucial to this modern age of industrial automation. In lieu of changing the wiring to an array of relays every time an update is needed, the PLC can be updated merely by reprogramming. Omron is one company that produces these PLCs. Paying homage to the classic diagrams used to wire up traditional relay-based control systems, the programs for Omron PLCs are written graphically by the user through ladder logic diagrams that are then translated into instructions understood by the PLC.
Load the programming software. There are different families of Omron's PLCs, so you will have to use the program that is compatible with your PLC. One such program is CX-Programmer.
Load or produce a ladder logic diagram. Using the classic “Open” command common for many Windows programs, locate the appropriate file and load it. Otherwise, create a new ladder logic diagram according to the instructions supplied with the software package.
Verify your ladder logic diagram. Make sure that you have no blank rungs that would essentially constitute short circuits. Also, be sure the inputs and outputs that you have specified are correct according to your program and the limitations of your specific PLC.
Set up the PLC to communicate with the computer. Depending upon the family of PLC you are programming, the connectors will be different. The end that connects to the computer may be a USB or D-Sub connector, while the connection to the PLC may be a USB, D-Sub or CS/CJ-series connector.
Download the ladder logic program to the PLC. You will need to execute the “Work Online” command. The keyboard shortcut of Ctrl+W will establish communication between the computer and the PLC. At this point, you will have to follow the directions for your specific software package in order to transfer the program to the PLC.
Test the PLC program. Either with the PLC still communicating with the computer or with it now disconnected and instead connected to the hardware it is to control, run the PLC program and test all inputs, such as switches and sensors, to verify that the outputs from motors, solenoids and the like are correct. If corrections have to be made, repeat the process from changing the ladder logic diagram through downloading the updated program to the PLC.