4 steps to follow when commissioning a PLC system 

The commissioning of a system can be divided into four stages:
  • Material check
  • Transfer and test the software
  • Software optimization
  • Commissioning of the entire system

1. Checking the equipment

Each sensor, switch and button is connected to a specific input and each actuator to an output. During the engineering process, addresses and wires should not be mixed up. In addition, the sensors and the location of the actuators should be verified (whether they are where they should be in the automated system).

During the verification procedure, the outputs are set in a test mode . The actuators must then meet the specified requirements (functions). If changes are made, the documentation (allocation list, drawings, etc.) must also be updated to reflect reality

1.1 Testing inputs and outputs

Input devices , for example. switches, can be manipulated to give the open and closed contact conditions and the corresponding LED on the input module observed. It should be on when the input is closed and not on when it is open.


Failure of an LED to light could be because the input device is not functioning properly , the wiring connections to the input module, the input device is not properly powered, or the LED or module. input is defective. For output devices that can be safely started, push buttons may have been installed to allow testing of each output.


2. Software transfer and testing

Before commissioning, all available virtual and offline PLC strong>program testing tools should be used extensively to find program errors. This test tool can be found in STEP 7, for example, as an S7-PLCSIM subroutine. It simulates the work of a PLC (virtual PLC) and allows testing of the PLC program written by the user.

Then the program is transferred to a central processing unit of the virtual PLC. The entire program is executed without using the real PLC .

The user should simulate the input signal changes and check how the outputs react to them. Some PLCs offer simulation in a real PLC: the entire program is executed in a PLC without the real inputs and outputs being connected. The processing of the PLC outputs therefore only takes place in the PLC image table. Controller physical I / O is not updated to / from controller I / O images.

Therefore, this eliminates the risk of damaging machines or parts of the system .

After that, the different parts of the user program and the system functions are tested: manual operation, adjustment, individual monitoring programs, etc. and finally interaction of the parts of the program using the main program.

The system can and should be commissioned step by step . Important aspects of commissioning and fault Detection functions are the test functions of the programming system, such as one-step mode or setting of breakpoints. The single step mode is particularly important because the program in the PLC memory is executed line by line or step by step. In this way, any program faults that may arise in the program can be immediately located.

3. Software optimization

User programs can almost always be improved after the first test . It is important that any corrections or modifications are made not only in the PLC user program, but also in the documentation.

4. Commissioning of the entire system

This already happens in part during the test and optimization phase. Once the final status of the PLC user program and documentation is established, all controllers are operational (according to the automation task). must be performed step by step again .

If no faults occur during the complete commissioning of the system, it is ready for delivery to the customer.