MDS Wireless PLC and SCADA data transmission radio system in the Waterworks
S7-200 PLC to the terminal for the on-site water supply wireless dispatch system composition and function. And focus on the PLC Modem with Wireless Interface and PLC software design into the analysis and explanation, given some of the process flow diagram and system applications.
Programmable Logic Controller (PLC) Monitoring data radio communication interface IPC MCGS configuration software
an overview of
a water plant control systems located in more than ten kilometers from the five deep water pumping stations, storage tanks, a network of user control. Gap between the level of the water supply system up to 150 meters, due to the water supply system, the special structure of the composition and topography, the last artificial control, to production management, water supply scheduling inconvenience.
implemented a computer monitor because it can real-time monitoring of the main parameters of the water supply system (such as pressure, flow, level, voltage, current, etc.), control of deep well pump, to monitor the operational status of pumps, while providing the necessary production management statements, curve, data query functions. It runs on the safety of water supply systems, scientific control of great significance.
computer monitoring system uses the master-slave structure of distributed wireless real-time monitoring method (referred to as SCADA), shown in Figure 1.
system consists of monitoring centers, wireless communication systems, on-site monitoring devices, sensors and instrumentation in four parts.
control center: the computer, MCGS configuration software, wireless data radio, omni antenna, and UPS mimic panel composed of the main terminal to complete the on-site real time data acquisition, monitoring, control, data storage, printing reports, data query and so on.
wireless communication system: pump station monitoring center and the use of wireless communication terminals. Monitoring center to active stations, and other passive terminal station from the station vice, the system uses radio management committee given the data frequency to one way and from the station-to-multipoint communication, control centers for the omnidirectional antenna, the deputy station directional antenna.
site surveillance terminal: the core of the PLC, is an intelligent device, it has its own CPU, and control software, mainly to complete the field data collection, conversion, storage, alarm, control and other functions, and with the monitoring center via wireless channel Microcomputer data communications. According to the order of the respective control center system self-test, data transfer, control output and other tasks.
sensors and instrumentation: a PLC signal to monitor on-site “Eyes”, the scene all the signals are subject to change through the sensor and the instrument can output standard signals, the terminal has been accepted by PLC. System is mainly measuring voltage, current, level, pressure, flow and power consumption parameters.
Well lose control of water pumps l manual control. Operator on the basis of the input pump clear water tank level to start and stop operation.
l control. PLC under the clear water tank level and the input pump start and stop the water level of the input pump in the automatic mode to start and stop operation.
Third, on-site PLC terminal
scene PLC control terminal is the industrial field and a bridge link between the monitoring center, on the one hand it is acquiring the instruments, transmitters, signal equipment, such as running, on the other hand it communication with the monitoring center, the implementation of the order. On-site terminal generally unattended. Therefore, the terminal s performance and quality of a great impact on system reliability. After full argument, use of Siemens S7-200 series PLC to the terminal site has a high cost performance, it has a small, easy to expand, excellent performance characteristics, is ideal for small-scale on-site monitoring.
1, PLC hardware design
site require monitoring and control of a terminal input signal switch, the switch output signal path analog input signal. Therefore, we choose the basic unit of S7-212, analog input expansion module (EM231), analog output expansion module (EM232). Meet site requirements.
2, communication interface
from the station PLC and radio communications: S7-214PLC basic unit of a RS-485 interface with the wireless channel for data transmission machine (power, data radio) is connected, we have designed a dedicated RS-485 Interface Modem and the use of photoelectric isolation technology, so the two are completely independent in the electrical and avoid mutual interference, as when data transfer plane firing RTS signal, the RS-485 interface, not Tigong RTS signal, two methods to resolve this issue. First, the Wireless Modem PLC launch information generated under the RTS signal, which requires the Modem must be intelligent, while PLC required before sending the message first and Modem communications, let the output signals RTS and RTS have been generated to send back information, then PLC and then send the site information. Second, the use of a PLC I / O output point, RTS signal generated by the PLC is connected before sending information to the point, the control data transmission machine launch, after a period of delay (the establishment of the carrier radio time), then send information. The latter method is simple, practical, better solve the problem of wireless communication interface. The news of two, currently incolor = red> 1????1 2