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From Reliability to Flexibility: Why PLC Control Systems Are Essential in Industrial Automation 1756-ENET/A/1756-CN2/A/1756-L62/1756-DHRIO/1768-M04SE

In order to adapt to the use of industrial environment, compared with general control devices, PLC machines have the following characteristics:
1. High reliability, strong anti-interference ability Industrial production reliability requirements for control equipment:
① The mean time between failures is long  (1756-M16SE/MVI56-MCMR/1756-M08SE/1768-CNBR/1747-SDN/1734-SSI/1786-RPFM)

② The average repair time is short  (1756-L71/1747-L552/MVI56E-MCMR/1746-NR8/1734-485ASC/1756-OB16E/1734SC-IF4U/1734-VHSC24/1794-PS13)

The failure of any electronic equipment is usually of two kinds:
① Accidental failure. Due to the external harsh environment such as electromagnetic interference, ultra-high temperature, ultra-low temperature, overvoltage, undervoltage, vibration caused by the fault. This type of failure, as long as it does not cause damage to system components, once the environmental conditions return to normal, the system will also return to normal. However, for the PLC, after external influence, the internal stored information may be destroyed. (1756-L73S/1769-L30/1769-OF4VI/1746-BSN/1786-RPCD/1786-RPFS/1769-ADN/1756-L75/1794-AENTR/1769-OF4CI/1747-SCNR/1756-OB16D/1794-IT8/1769-SDN/1756-L71-L72-L73-L74-L75)

② Permanent failure. Failure due to unrecoverable damage of components. If you can limit the occurrence conditions of accidental failures, if you can make the PLC in the harsh environment is not affected or can limit the consequences of the impact to the minimum range, so that the PLC automatically returns to normal after the bad conditions disappear, so that the average time between failures can be improved; If some diagnostic measures and appropriate protection means can be added to the PLC, when the permanent failure occurs, the fault can be quickly detected and the fault is limited to the local area, which can reduce the average repair time of the PLC. To this end, the PLC manufacturers have taken a variety of measures in hardware and software, so that in addition to PLC itself has a strong self-diagnosis ability, can give error information in time, stop running and wait for repair, but also make PLC has a strong anti-interference ability.(1756-M02AS-EN2F-DNB-CNB-DHRIO-CN2R-CN2-OF8I/1756-PA75-PA72-PB72-PB75-PB75R-PA75R-A4-A7/1756-L71S-L72S-L73S-L81ES-L82ES-L83ES-L84ES/1747-L553-L552-L551-AENTR-BSN-L531-L532-L541/1794-IB32-OB32P-IT8-IE8-IR8-PS3-PS13-VHSC/1783-EMS08T/1756-L81E-L82E-L83E-L84E-L85E-L8SP)

Hardware measures: The main modules all use large-scale or ultra-large-scale integrated circuits, and a large number of switching actions are completed by contactless electronic memory. The I/O system is designed with perfect channel protection and signal conditioning circuits.
① Shielding - For major components such as power transformers, cpus, programmers, etc., the use of conductive and magnetic conductive materials for shielding to prevent external interference.

Filter - The power supply system and input lines use a variety of forms of filtering, such as LC or π filter network, to eliminate or suppress high-frequency interference, but also weaken the interaction between various modules.(1756-IA16I-HYD02-EWEB-HSC-ENBT-CFM-OB16E-IB16D/1747-L541-L542-L543-L551-L552-L553/1756-IF4FXOF2F-OF6CI-OF6VI-IR6I-IT16-IT6I-IF8I/1756-SYNCH-TIME-OV32E-OX8I-IB32-OB32-IB16/1756-OW16I-IM16I-OB8-IB16I-OB16I-OB16D-IA32)

② Power adjustment and protection - The +5V power supply required by the core component of the microprocessor is adjusted by multistage filtering and integrated voltage regulator to adapt to the fluctuations of the AC power grid and the influence of overvoltage and undervoltage. (1768-PA3-PB3-L43-L45-L45S-L43S-ENBT/1769-L24ER-QB1B-L24ER-QBFC1B-L27ERM-QBFC1B/1769-L18ER-BB1B-L19ER-BB1B-18ERM-BB1B-32E-35/1734-IE2C/1734-OE2V/1734-OE4C/1756-L73/1756-BA1)

③ Isolation - between the microprocessor and the I/O circuit, photoelectric isolation measures are used to effectively isolate the electrical connection between the I/O interface and the CPU, reducing failures and misactions; I/O ports are also isolated from each other.(1746-NR4-NI4-NO4I-NIO4I-NT4-P2-P4-HSCE2-HSCE/1746-NO8I-NT8-NR8-NI16I-NI8-NO8V/1794-ID2-IE8XOE4-ACNR15-IM16-IF4I-OF4I-IT8-IE/1769-PB4

/1769-IF4I)

④ The use of modular structure - this structure helps in the case of failure short-term repair. Once a module is found to be faulty, it can be quickly replaced to restore the system to normal work; It also helps to find the cause of the failure faster.(1756-IB16IFK/1756-IB16IF/1756-IN16/1769-IR6/1769-HSC/1768-PB3/1768-L45-L43-L43S-L45S-ENBT-PA3-PB3/1768-L43-L45-L43S-L45S-ENBT-CNBR-PA3-PB3-EWE/1797-IRT8-OB4D-OE8-OE8H-PS1E-RPA-RPFM-IE87-O)

Software measures:
Has a strong self-test and protection function.(1769-L33EMS-L36ERMS-L30EMS-16ER-BB1B-18ER-BB/1756-OF8-IF16-OF4-IF8-IF8H-IF16H-IR12-IT16-IRT8I/1756-A4-PA75-PB75-IF16H-IF8H-IF8I-OF8I-IT16
1756-L73-L71-L72-L74-L75-L7SP-EN2T-CN2R-OA16I-OV32E)
① Fault detection - the software regularly detects the external environment, such as power failure, undervoltage, lithium battery voltage is too low and strong interference signals. For timely processing.
② Information protection and recovery - when the occasional failure conditions appear, do not destroy the PLC internal information. Once the fault condition disappears, you can return to normal and continue to work with the original program. Therefore, when the PLC detects the fault condition, it immediately stores the current state into the memory, and the software collaborates with the memory to seal it, prohibiting any operation of the memory to prevent the stored information from being washed away.
③ Set alarm clock WDT (watchdog) - If the program each cycle execution time exceeds the WDT specified time, indicating that the program enters a dead loop, immediately alarm.
④ Strengthen the inspection and verification of the program - once the program is wrong, immediately alarm and stop execution. ⑤ Battery backup for programs and dynamic data - After the power failure, the use of backup battery power supply, the relevant status and information will not be lost.

Among the factory test projects of PLC, there is one that is anti-interference test. It is required to withstand interference pulses with a amplitude of 1000V, a rise time of 1nS and a pulse width of 1μS. In general, the average time between failures can reach hundreds of thousands to tens of millions of hours; The finished system can reach 40,000 to 50,000 hours or even longer.(1747-L553-L552-L551-AENTR-ASB-L541-L542-L543/1794-AENT-AENTR-IE8-IF4I-OF4I-IT8-IR8-IE12/1794-IE12-OE12-OE8H-IF8H-IRT8-IRT8I-OE4-IP4/1783-BMS10CL/1783-MX08T/1756-SYNCH/1747-SDN/C)

2. Strong versatility, variable control program, easy to use PLC a complete variety of hardware devices, can be formed to meet various requirements of the control system, the user does not have to redesign and manufacture hardware devices. After the user determines the hardware, in the case of production process changes or production equipment updates, it is not necessary to change the PLC hardware equipment, just adapt the program to meet the requirements. Therefore, in addition to being used in single-machine control, PLC is also widely used in factory automation.

3. Strong function, adapt to a wide range of modern PLC not only has logical operation, timing, counting, sequence control and other functions, but also has digital and analog input and output, power drive, communication, man-machine dialogue, self-test, record display and other functions. It can control a production machine, a production line, and a production process.(1797-IE8-ACNR15-BCNR-BIC-BOOT-IE8H-IE8NF-IJ2/1764-24BWA-28BXB-24AWA-LRP-LSP)

4. Programming is simple and easy to master At present, most PLCS still use the "ladder diagram programming method" in the form of relay control. It not only inherits the clear and intuitive nature of the traditional control line, but also takes into account the reading habits and programming level of most factory enterprise electrical technicians, so it is very easy to accept and master. The symbol and expression of the programming element of ladder diagram language are quite close to the schematic diagram of relay control circuit. By reading the PLC user manual or short-term training, electrical technicians and technicians can quickly learn to use ladder diagram programming control program. At the same time, it also provides programming languages such as function diagram and statement table. When the PLC executes the ladder diagram program, it translates it into assembly language with the interpreter and then executes it (the interpreter is added inside the PLC). Compared with the user program written in assembly language directly, the time of executing ladder diagram program is longer, but for most electromechanical control equipment, it is insignificant, and it can fully meet the control requirements.(1797-IBN16-IE8-IE8H-IRT8-OB4D-OE8-OE8H-IRT8/1769-L32E-L35-L33ER-L30ER-L30ERM-L33ERM-L36E)

5. Reduce the workload of design and construction of the control system Because PLC adopts software to replace a large number of intermediate relays, time relays, counters and other devices in the relay control system, the design, installation and wiring workload of the control cabinet is greatly reduced. At the same time, the PLC user program can be simulated and debugged in the laboratory, which reduces the debugging workload on the site. Moreover, due to the low failure rate and strong monitoring function of PLC, modularity, etc., the maintenance is also very convenient.(1769-L24ER-QB1B-L24ER-QBFC1B--L27ERM-QBFC1B/1746-NR8-NT8-NI8-NO8I-NO8V-NI16I-P3-OV32E)

6. Small size, light weight, low power consumption, easy maintenance PLC is the microelectronics technology applied to industrial equipment products, its compact structure, strong, small size, light weight, low power consumption. And because of the strong anti-interference ability of PLC, it is easy to be loaded into the equipment, and is the ideal control equipment for mechatronics.(1769-L18ER-BB1B/1769-L35E-L32E-L33ER-L30ER-L36ERM-L33ERM-L30)

PLCs are essential tools in industrial automation, delivering high reliability, flexibility, and broad functionality. From minimizing environmental interference to simplifying programming and reducing installation work, PLCs offer unmatched efficiency and ease of use. Their compact and rugged designs make them ideal for a wide range of industrial applications, ensuring they remain a critical component of modern automation solutions.

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