Troubleshooting and Handling of Programmable Logic Controller PLC

During the long-term operation of the plc system, some failures may occur. PLC’s own faults can be judged by self-diagnosis, and external faults are mainly analyzed according to the program. Common failures include power system failure, host failure, communication system failure, module failure, software failure, etc.
1. Overall inspection and treatment of common faults
The purpose of the overall inspection is to find out the general direction of the fault point, and then gradually refine it to determine the specific fault point and achieve the goal of eliminating the fault Purpose. The general inspection and handling procedures for common faults are shown in Figure F-2-1.
Check power supply and RO failure 2 /STRONG>
PLC system host power supply, expansion machine power supply, power supply in the module, if any power supply is abnormal, it must enter the power failure inspection process. If all parts function normally, it can only be that the LED display is faulty, otherwise the external power supply should be checked first. , if there is no fault in the external power supply, then check the fault in the internal power supply of the system. The inspection sequence and content are as described in Table F-2-1.
Table F-2-1

3. Abnormal fault inspection and treatment
The most common faults of the PLC system are stop running (the running indicator light is off), cannot start, and work cannot be carried out, but the power indicator light is on. In this case, abnormal fault checking is required. Check the order andSee table F-2-2.
Table F-2-2

4. Check and deal with communication faults
Communication is the basis of PLC network work. The master station of the PLC network, the communication processors and communication modules of each slave station have normal working indications. When the communication is not normal, it is necessary to check the communication fault. The inspection sequence and content are shown in Table F-2-3.
Table F-2-3

5. Input and output failure inspection and treatment
The input and output modules are directly connected with external equipment, which is a part prone to failure. The damage is often caused by external reasons. If the cause of the fault is not found out in time and the fault is eliminated in time, it will do great harm to the PLC system. The inspection sequence and content are shown in Tables F-2-4 and F-2-5.
Table F-2-4

Table F -2-5

4 Installation Status Each Whether the unit is fixed reliably
Is the connector of the cable fully inserted?
Is the screw of the external wiring loose? No looseness
No looseness
No abnormality
5 Life components Batteries, relays, memory, etc. are subject to the specifications of each component

F.4 Troubleshooting Guide for Programmable Logic Controller
There may be some particularity for the specific PLC fault inspection. The fault inspection and processing methods of the S7-200 are given below. See Table F-4-1.
Table F-4-1

should say PLC is a highly reliable and stable controller. As long as it is installed and used according to its technical specifications, the probability of failure is extremely low. However, once a fault occurs, it must be checked and dealt with according to the above steps. In particular, check for damage due to malfunctioning external equipment. Be sure to find out the cause of the fault, and try to run it after the fault is eliminated.