Introduction: With the continuous development of automation technology, customers need to conduct more accurate and in-depth monitoring of the working conditions of field equipment. The communication method used has developed from traditional serial communication to the current mainstream Ethernet bus communication. The operating environment is harsh and limited by on-site conditions. When it is necessary to realize remote equipment monitoring: whether it is serial communication or Ethernet bus communication, the range of data transmission is limited. For this reason, GPRS wireless communication technology came into being. . Yike proposes a wireless communication scheme based on HMI and GPRS technology, making full use of GPRS wireless network to realize wireless transmission of data and information, so as to effectively monitor the working conditions of field equipment. This paper takes the fire inspection instrument as an example to introduce the remote data communication scheme based on HMI products, PLC products and GPRS wireless communication technology.
1. Overview of the automatic control system of the fire inspection instrument
The fire inspection instrument can be applied to various buildings including buildings, office buildings, gymnasiums, hospitals, government agencies, etc., in order to achieve the purpose of improving the safety and reliability of fire water supply systems in buildings. Main realizations: 1. When carrying out equipment inspection of fire fighting equipment, fortify the overpressure device.
2. Inspection of electrical control system and electric valve inspection.
3. Regular automatic low-frequency, low-speed and no-pressure inspection of fire pumps.
4. Sewage pump inspection of fire pump room: When there is no sewage discharged from the pump room for a long time, the sewage pump rusts and rusts from time to time, and it cannot operate normally, resulting in a large amount of water in the pump room, damage to fire fighting equipment, and paralysis of the fire fighting system. , the fire inspection instrument can avoid this situation.
In order to further improve the real-time monitoring of the site, the GPRS wireless communication technology is added to the original system, and the characteristics of the GPRS network, such as wide coverage and low maintenance cost, are fully utilized to realize the remote monitoring of on-site monitoring data, equipment operation history data and fault alarm information. Wireless transmission.
2. Introduction of control system
The current design of the fire automatic inspection instrument is mainly composed of HMI, PLC, inverter, micro printer and GPRS wireless module. With the help of HMI products, it has the function of multiple serial ports and can communicate with various devices at the same time. PLC, printer and GPRS module products are connected to HMI. On the one hand, it can simplify the system architecture and reduce the system cost. On the other hand, in addition to transmitting on-site data, it can also complete the transmission of on-site information, such as event information or alarm information. Its electrical control system can realize:
1. Liquid level alarm function
Automatically shut down at low water level, automatically start when the water level is restored, automatically alarm when the water level is abnormal, query historical records, store tens of thousands of fault information, and automatically print.
2. Fault alarm function
The equipment on-site sound and light alarm, the on-site fire control room alarm, can be networked with the remote fire control room to realize remote data transmission and remote control.
3. Inspection record query function
The cycle of equipment fire inspection and the time of each fire inspection can be set by the HMI product on site. At the same time, the total number of inspections of the equipment, the date of the last inspection and the date of the next inspection can be checked.
4. Fire pump control function
The fire signal is automatically activated, replenished, and the main pump fails and the backup pump is automatically put into operation.
5. System authorization function
Authorize engineers and operators at different levels, and give engineers higher rights. They can modify system parameters on the man-machine interface to achieve full access to the entire system, while only granting monitoring rights to operators and cannot modify system parameters, thereby preventing unauthorized access. Mishandling by authorized personnel.
3. Hardware configuration
1. PLC control unit
PLC adopts ELCO C200 series 32/48-point host, with C200-DIO-BG01 24-point DI24-point DO (Transistor) hybrid module, C200-AI-0800U/I 12-bit current/voltage module, connected to HMI through RS232, At the same time, use the RS485 mode on the host to connect the inverter to complete the collection of on-site switch signals and the processing of analog data.
2. Human-machine interface unit
The HMI product adopts ELCO DEV series economical 10-inch human-machine interface DEV500T. This series of human-machine interface has the characteristics of rich colors, high resolution, high screen brightness and strong communication ability. It can use different serial communication methods at the same time to communicate with different devices. communication. In this control system, the C200 PLC is connected through the RS232 mode of COM0 to realize its monitoring and control, the micro-printer is connected through the RS232 mode of COM1, the fault alarm information is printed in real time, and the RS485 mode of COM2 and the custom serial port communication mode are connected. GPRS wireless module, when the designated mobile phone number is entered in the program screen of the man-machine interface, the directional sending of field data and fault information can be completed.
3. GPRS wireless module unit
The GPRS module adopts Beijing Chi Xunda SM10 series SM10LC-AB. This module has the characteristics of simple use, convenient installation and high reliability. After inserting the SIM card, it can send data and information wirelessly through simple configuration on the PC.
This control system puts forward higher requirements for the real-time communication, data processing and communication expansion capabilities of the touch screen when networking, and Eke C200 PLC has outstanding performance in the following two aspects:
1. By displaying and controlling the switching signals and analog signals collected by the C200 PLC, and optimizing the program, the serial communication delay time is reduced, and the real-time refresh of the collected signals on the touch screen is guaranteed.
2. By developing the macro code program on the touch screen (mainly using C language programming), when the PLC collects the fault signal, the touch screen displays and prints the real-time fault information, and converts the fault information message from hexadecimal ASCII code to ASCII code. The special Unicode code of the GPRS network is sent to the GPRS module to realize the wireless transmission of the fault information, so that the remote engineering personnel can keep abreast of the on-site work situation.
4. System Features
Using advanced software and hardware, the man-machine interface can Display the entire system status, on-site alarms, collect analog trend data, operation logs, etc., and can intuitively and dynamically Display the changes of important parameters on site, and realize human-computer interaction. Using GPRS network to wirelessly transmit data, the remote terminal can monitor the scene, making the further intelligent application of the scene data a reality.
2. High reliability
The whole system is reasonably priced and easy to maintain. Compared with the traditional radio transmission, the GPRS network has stronger anti-interference ability for data transmission, and the communication coverage is much larger than the former. good features.
3. Excellent openness
Network through GPRS network to realize data exchange between GPRS sites, and use the C language function in the man-machine interface configuration software to develop new communication drivers, which can communicate with devices using custom communication protocols , and can also realize the conversion of different data formats.
Compared with the original traditional control system, the wireless communication solution based on HMI and GPRS technology provided by Yike can further reduce the on-site maintenance personnel, reduce the cost of the enterprise, improve the economic benefit of the enterprise, and at the same time have better anti-interference and data transmission. safety. This solution will be widely used in industries that use wireless remote data monitoring, such as urban pipe network, heat network, petroleum, and electric power.
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