For the on-site hardware configuration and software debugging of various PLCs, experienced engineers should first spend some time making a simple plan for their on-site work, which should generally involve the following steps:
(1) System planning
First, it is essential to thoroughly understand the functions required by the system and investigate possible control methods. At the same time, it is necessary to discuss the best operating procedures with users or design institutes. Based on the conclusions drawn, a system plan should be formulated, and the PLC system architecture, the number of I/O points, and the type of I/O modules to be adopted should be determined.
(2) I/O module selection and address setting
Once the I/O module is selected, the PLC's CPU system will automatically set the I/O address according to the planned I/O point usage, or the user can define the I/O module address.
(3) Ladder diagram programming and system wiring
After determining the actual I/O addresses, the ladder diagram program is written according to the system's functional requirements. Simultaneously, with the I/O addresses configured, system wiring can also begin.
(4) Simulation and modification of ladder diagram program
After the ladder diagram program is written, it is written to the PLC. An online connection can then be established between the PC and the OpenPLC system to perform online simulation. If the program malfunctions, debugging must be performed and the ladder diagram program modified.
(5) System commissioning and actual operation
If the ladder diagram program executes correctly and the system wiring is completed in the online simulation, the system can be put into actual operation, and the project plan will be completed.
(6) Program comments and archiving
To ensure convenient future maintenance, the ladder diagram program that has been tested and is ready for actual operation should be annotated and organized for archiving. This will shorten the time required for future maintenance and program retrieval. This is a good habit of professional engineers, which will bring great convenience whether you are performing maintenance yourself or handing it over to users, and it is also a reflection of your professional level.
In the above tasks, complex system planning may take several days or even longer, but simple system planning in the hands of a programming engineer with good professional habits may only take a few hours.
One issue that needs to be emphasized here is very simple yet occurs in almost every project: PLC wiring. This is often overlooked by inexperienced engineers. In fact, most of the problems and workload during on-site commissioning lie in wiring. Experienced engineers should first check the wiring in the field.
Typically, if the on-site wiring is done by the user or other construction personnel, the quality of the wiring can be roughly judged by looking at the wiring diagram and the appearance of the wires. Then, a complete and careful inspection of all wiring is necessary. On-site PLC burnout due to wiring errors has occurred frequently; a thorough inspection is essential before any actual commissioning. Even if wiring is not your job, checking the wiring is your duty and responsibility, and it can save you a significant amount of time later.
