PLC Control Cabinet

Product Overview

PLC control cabinet refers to a complete set of control cabinets, which can realize the automatic action of motors, switches and other equipment, and can also be a signal processing cabinet for receiving, processing and storing external signals.

PLC control cabinets are fully functional and compact in structure. They can be combined according to the actual control scale and have functions such as overload and phase loss protection. It can not only realize the automatic control of a single cabinet, but also realize a distributed control system composed of multiple cabinets through industrial Ethernet or industrial field bus network. It can adapt to various industrial automation control occasions and is widely used in metallurgy, electricity, ports, municipal construction, environmental protection and other industries, such as sewage treatment, constant pressure water supply, pipe gallery engineering, cooling water circulation, smart pump station, fresh air air conditioning and other automation application control scenarios.

PLC control cabinet can complete equipment automation and process automation control, realize the characteristics of perfect network function, strong anti-interference ability, stable performance and scalability, and is the core and soul of modern industry.

1、open

A main air switch controls the power supply of the entire cabinet.

2、Weak power supply

The 24VDC switching power supply provides stable power output for the PLC system and can also provide power for various external sensors.

3、PLC

Choose PLCs of different models and specifications according to project requirements. PLC is the core brain of the control cabinet.

4、Terminal Blocks

It can be configured according to the number of signals. If it is just a simple PLC control cabinet, these things are basically needed. If other devices in the control cabinet are required, it depends on the situation.

5、Relay

Sometimes the instructions sent by the PLC need to be transferred by the relay first. When the instructions are issued, the relay will act, so that the nodes of the control loop are connected to the normally open or normally closed points of the relay.

Power supply: DC 24V, single-phase AC 220V, (-10%, +15%), 50Hz.

Product functions and features

1. Controlled by a programmable controller (PLC). 2. Manual and automatic dual control. 3. Simple wiring and easy operation.

When the Programmable Logic Controller is put into operation, its working process is generally divided into three stages, namely input sampling, user program execution and output refresh. Completing the above three stages is called a scan cycle. During the entire operation process, the CPU of the PLC repeats the above three stages at a certain scan speed.

1. Input sampling stage

In the input sampling stage, the PLC reads all input states and data sequentially in a scanning manner and stores them in the corresponding units of the I/O image area. After the input sampling is completed, the user program execution and output refresh stages are transferred. In these two stages, even if the input state and data change, the state and data of the corresponding units in the I/O image area will not change. Therefore, if the input is a pulse signal, the width of the pulse signal must be greater than the scan cycle to ensure that the input can be read in any case.

2. User program execution stage

In the execution stage of the user program, the PLC always scans the user program from top to bottom. When scanning each ladder diagram, always scan the control circuit composed of the contacts on the left side of the ladder diagram first, and perform logical operations on the control circuit composed of the contacts in the order of left first, right second, top first, bottom second. Then, according to the result of the logical operation, refresh the state of the corresponding bit of the logic coil in the system RAM memory area; or refresh the state of the corresponding bit of the output coil in the input/output image area.

That is, during the execution of the user program, only the state and data of the input point in the I/O image area will not change, while the state and data of other output points and soft devices in the I/O image area or system RAM storage area may change, and the program execution result of the upper ladder diagram will affect the ladder diagram below that uses these coils or data; on the contrary, the state or data of the logic coil refreshed in the ladder diagram below can only work on the program above the ladder diagram until the next scan cycle.

3. After the scanning of the user program is completed in the output refresh phase, the PLC will enter the output refresh phase. During this period, the CPU refreshes all output latch circuits according to the corresponding state and data in the I/O image area, and then drives the corresponding peripheral devices through the output circuit. This is the real output of the PLC.