PLC design of the hottest HVAC monitoring system

2022-08-05
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PLC design in HVAC monitoring system

clean room is the key facility for LCD production, in which HVAC (heating, ventilation and air conditioning) system is very important for clean room environment. The HVAC control system includes the control of cold and heat source units, air conditioning units and air conditioning terminal equipment. The HVAC monitoring system monitors in real time the start and stop of heating and ventilation and air conditioning equipment in the clean room, as well as the alarm of electric leakage and water leakage. At the same time, it monitors the temperature, humidity and pressure of various parts of the clean room, as well as other parameters such as the temperature, pressure, flow and frequency of the equipment, and alarms for faults The equipment startup and shutdown status and analog quantity data are recorded and saved at any time, so that the central monitoring personnel can timely handle the corresponding alarms according to the real-time data displayed by the monitoring system, analyze and do the corresponding early warning according to the data trend chart, and analyze the system fault causes according to the historical data recorded by the system

project status

s plant is divided into three plants: array, box and module according to its production process, and the power plant responsible for the power supply of the whole plant. Due to the large area of the plant, the product equipment for heating and ventilation in the dust-free room is scattered in all parts of the plant, and the signal points to be monitored cannot be centralized in one station. Therefore, the supervisory control and data acquisition (SCADA) system based on PLC is adopted

according to the equipment distribution in the plant, set up multiple sub stations in each area: 2 Box sub stations, 2 module sub stations and 6 array sub stations to collect the surrounding data to be monitored; The factory has two monitoring rooms. The array monitoring room is equipped with two monitoring master stations, "box forming module master station plc1" and "array master station plc1" to monitor the information of box forming module plant and array plant respectively. The power monitoring room is equipped with "power master station plc1" to monitor all the information including box forming module and array plant at the same time

the specific distribution of each station is shown in Figure 1

the data collected by each PLC substation distributed in the plant site will be transmitted to the PLC master station of each monitoring room through the network, and then the upper monitoring computer will connect to the master station PLC, and the relevant information of the whole plant site will be monitored and recorded through the upper industrial monitoring software

plc hardware configuration

1. the PLC of each station adopts the current CS1 model PLC product of OMRON company

and its main features include the following

(1) advanced performance: further improve the computing power, the highest computing speed in the industry at present. Industrial 32-bit reduced instruction system CPU, basic instruction processing speed up to 0.02 μ s。 The built-in program capacity of CPU can reach 250K steps, the data capacity can reach 448k words, and the capacity of external memory card can reach 64MB. The number of local rack control points can reach 5120. With remote i/o, the control points can reach more than 100000

(2) various application related instructions: there are a variety of special instructions without complex programming. With self-tuning PID command, double precision command, fault diagnosis command and stack command, mineral products will be affected by many factors such as logistics conditions when they are transported to the domestic market

(3) integrated development environment and intermediate software: from program development to simulation, network communication and touch screen software, they are all integrated in a unified software package, which is very convenient

(4) good openness and seamless network system: from the information layer to the control layer and then to the equipment layer, CS1 supports seamless and transparent information communication between multi-layer networks that comply with international standards. The supported network types mainly include Ethernet, controllerlink, PROFIBUS DP, DeviceNet, MODBUS, can, etc

(5) it is more convenient to connect with third-party devices: the protocol macro function of CS1 can easily interconnect with multiple third-party devices with different protocols

(6) inheritance and Maintainability: the new system is compatible with the old system and easy to upgrade; The CPU supports battery free operation and remote maintenance, which is very convenient for maintenance

(7) system function expansion can be realized: various PLC based process control automation systems, high-precision positioning, remote monitoring, fieldbus network systems, etc

CPUs of different grades can be selected according to the load of PLC in the substation and master station: the PLC in the substation only processes local data with a small amount of data, and the CPU adopts Omron CS1 series cs1h-cpu44h; The master station needs to process the data transmitted from the PLC of each substation of the whole plant, with a large amount of data. The CPU adopts cs1h-cpu67h with the strongest performance of OMRON CS1 series, which has the fastest instruction processing speed and the largest program and data capacity

2. each substation shall configure corresponding digital input (DI) module and analog input (AI) module according to the number of field collected signals

(1) digital input module (DI)

- 64 points: cs1w-id261 is shown in Table 1

- 96 points: cs1w-id291 is shown in Table 2

(2) analog input personnel less input module (AI)

- 8 points: cs1w-ad081-v1

- input points: 8 channels

- input range: 0~5v, 1~5v, 0~10v, -10~+10v, 4~20ma optional

- resolution: ≥ 13 bits (1/8000)

- isolation mode: photoelectric isolation

- conversion speed: 1ms/point

- accuracy (25 ℃): voltage ± 0.2% current ± 0.4%

- other functions: line break detection, peak holding, average value function, calibration function, etc

- external connection: removable terminal strip is adopted to improve reliability and facilitate connection and maintenance

network architecture

1 On site Layer-1 PLC network

Omron controller is used to link the optical fiber redundant link between the PLC of each substation on site and the PLC of the main station of the monitoring room: the PLC of the four stations on the boxing module site and the boxing module main station plc1 located in the array monitoring room form an optical fiber ring. Through the boxing module field Layer-1 network CLK1, the data collected by each PLC on the boxing module site are collected to the boxing module main station plc1 for monitoring display; The six array site station PLCs and the array master station plc1 located in the array monitoring room form an optical fiber ring. Through the array site layer 1 network CLK1, the data collected by the array site PLCs are collected to the array master station plc1 for monitoring display

2. Monitoring layer-2 P and LC network

through the field Layer-1 network, the data collected by the field PLC are collected to the two main stations plc1 in the array monitoring room. The power monitoring room monitors and displays the data of the whole plant by monitoring the two-layer network CLK2 between the power master station 1, the box forming module master station 1 and the array master station 1, and centralizes all the field data collected by the box forming module master station 1 and the array master station 1 to the power master station plc1 to complete the monitoring and display of the whole plant

3. The Ethernet

monitoring upper computer of the information layer communicates with plc1 of each master station in the monitoring room through Ethernet to display field data in real time and make data records

the Ethernet link of the information layer is shown in Figure 2

Figure 2 Ethernet link diagram of information layer

software composition

1. the upper industrial monitoring software

the upper industrial monitoring software adopts RSView 32 developed by Rockwell software company of the United States. RSView32 is an integrated and component-based man-machine interface software, which runs under windows95/98/2000/nt and other operating systems, and can monitor and control automatic equipment and processes. It can easily complete the formation of process monitoring screen, real-time data collection, trend record analysis, alarm report printing and other tasks. The software also has strong web browser integration function, embedded standard programming language (VB), help, support real-time video image and embedded word processing, spreadsheet and ActiveX text

the upper software is mainly used to monitor the main process parameters and operation status of the equipment in the form of process screen and table, set and monitor the adjustment parameters and process of the main control circuit on the screen, and record the trend, alarm and interlock values of the main instrument data

2. OPC server

before, the upper software connected with the field automation equipment needed to develop a special bottom communication interface, which was very inconvenient for practical application

now, as an effective connection between automation system, fieldbus, fieldbus equipment and office management application, OPC makes the data exchange between office and field equipment simple and standardized, greatly simplifies the system structure, and makes the original complex architecture simple and clear. The upper software only needs to pay attention to the data exchange with OPC server, No need to worry about the connection of specific equipment

opc (OLE for process control) is an industrial standard based on Microsoft's OLE (now active X), com (component object model) and DCOM (Distributed Component Object Model) technologies. OPC includes a set of standard sets of interfaces, attributes and methods for process control and manufacturing automation systems. Active x/com technology defines how different software components interact and share data. No matter what software or equipment is used in the process, OPC provides a common interface for communication between a variety of process control equipment

Omron SYSMAC OPC server is an OPC software specially used for Omron series PLC and other equipment. In this system, it is used for the data interface with the upper Software RSView32 to realize the data exchange between Rockwell RSView32 and OMRON PLC

3. The communication tool software

finsgateway is the communication interface tool software of OMRON PLC, which is mainly used for the management between the upper computer and various communication networks of PLC, and provides the data interface for establishing communication. In this system, it is mainly used for communication control and data management between the upper computer and PLC Ethernet. In the software, Omron PLC Ethernet can be set and service start and stop control

in this system, the physical connection between the monitoring host computer and the plc1 of each master station in the monitoring room is realized through Ethernet; SYSMAC OPC server exchanges data with PLC through PLC communication interface tool software finsgateway, and also with RSView 32 database, which becomes the software interface linking Rockwell RSView32 and OMRON PLC

the software link diagram is shown in Figure 3

c programming software

cx programmer is the software programming and debugging tool program of OMRON PLC. It runs under windows98nt2000 operating system and has a rich and simple operating environment and powerful programming and debugging functions. Omron's SYSMAC CS1 series PLC has a rich instruction system, including relay instructions, timer and counter instructions, calculation instructions (including trigonometric functions, exponents, power operations, etc.), data conversion, diagnosis, displacement registers, comparison, data transmission, program control, PID control and other instructions. These instructions can be used to complete the data acquisition, processing and transmission of the field environment and equipment parameters of the system. (end)

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