1. Power supply: The power supply is used to convert the alternating current into the direct current required inside the PLC, and most of the PLCs are powered by switching regulated power supply.
2. Central processing unit: The central processing unit (CPU) is the control center of the PLC and the core component of the PLC, and its performance determines the performance of the PLC. The central processing unit consists of a controller, combinators, and registers, all of which are concentrated on a single chip and connected to the input/output interface circuits of the memory via an address bus, a control bus. The role of the central processing unit is to process and run user programs, perform logical and mathematical operations, and control the entire system to make it coordinated.
3. Memory: Memory is a semiconductor circuit with memory function, and its function is to store system programs, user programs, logical variables and some other information. Among them, the system program is the program that controls the PLC to achieve various functions, which is written by the PLC manufacturer and solidified into the read-only memory (ROM), which cannot be accessed by the user.
4. Input unit: The input unit is the input interface connected to the PLC and the controlled equipment, and is the bridge for the signal to enter the PLC, and its role is to receive the signal from the main command element and the detection element. The types of inputs are DC input, AC input, AC and DC input.
5. Output unit: The output unit is also the connecting part between the PLC and the controlled equipment, and its function is to transmit the output signal of the PLC to the controlled equipment, that is, to convert the weak current signal sent by the central processing unit into a level signal to drive the executive element of the controlled equipment. The types of outputs are relay output, transistor output, and crystal gate output.
In addition to the above parts, PLC programmable logic controllers also have a variety of external devices depending on the model, which are used to help programming, realize monitoring, and network communication. Commonly used peripherals are programmers, printers, cassette recorders, computers, etc.
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The main characteristics of Hollysys LE series PLC
LE series is a new generation of high-performance small and medium-sized PLC products launched by Hollysys, which is suitable for small and medium-sized industrial equipment control and distributed long-distance monitoring applications. LE-PLC combines the compact structure of small PLC products with the abundant functional advantages of medium-sized PLC products, and can support up to 20 local IOs or long ...
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What should be paid attention to when cooperating with Lysys PLC-PLC and inverter?
1. Input of switch command signal
The input signal of the inverter includes a switch-type command signal that controls the operating status such as operation/stop, forward/reverse, section speed, and joging. Frequency converters usually make use of relay contacts or components with relay contact switching characteristics (such as crystals).
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Hollysys PLC - the design specification of PLC program
(1) Select the appropriate PLC model and I/O points, and select the special function module when there are special function requirements.
(2) Familiar with the selected PLC programming instructions and compilation software.
(3) Carry out soft component planning, including internal relays, holding relays, data registers, ...
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Troubleshooting steps of Hollysys DCS system
The steps of DCS system troubleshooting include:
(1) Check the fault caused by improper use.
Common types of operational faults include operator errors, terminal wiring faults, module installation faults, and power supply failures.
(2) Troubleshoot the improper operation of the DCS system ...
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Hollysys PLC - the isolation technology of the input/output loop of the PLC control system
1. Circuit isolation
The isolation of analog circuits is more complex, mainly depends on the accuracy requirements of the transmission channel, the higher the accuracy requirements, the higher the cost of the channel; However, when the performance requirements rise to the main contradiction, the isolation components should be selected based on performance, and the ...
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Hollysys DCS - How to deal with DCS system failure?
1. View the data on the monitoring screen
When the following situations occur, it means that there is a problem with the control system, and the microcomputer maintenance personnel should be notified immediately for maintenance, and the operator should go to the site to deal with it.
(1) Frequently changing data does not change for a long time, and several or all data do not ...
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Hollysys - Contribute to China's green development "Yizhuang Power"
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Whether it is a new unit or an upgraded DCS, the equipment of the system and controller should focus on the reliability and load factor (including redundancy) objectives. The load rate planning of the communication bus must be controlled within a reasonable range, and the load rate of the controller should be balanced as much as possible.
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Hollysys PLC - Classification and application of PLC
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2. In terms of networking, the DCS network is ...
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1. Preliminary preparations
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Hollysys OCS industrial optical bus control system was successfully applied in Sinopec project
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Hollysys delivered a keynote speech at CAIMRS 2023 and won a number of awards
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Hollysys successfully signed 16 sets of control system projects for 10 million tons of oil refining enterprises
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