Design of remote water supply control by wireless data transmission radio

　　1. Scheme selection

　　In industrial automatic control system, data transmission is the basis of realizing automatic control. Data transmission can be simply divided into wired (including erecting cables or renting special telephone lines) and wireless (including establishing special wireless data transmission system or using public network information platforms such as GSM and CDMA).

　　The cable wiring communication mode not only has the disadvantages of troublesome wiring, inconvenient maintenance and huge consumables, but also greatly increases the communication instability caused by long distance (such as signal interference and attenuation). Especially in the highly decentralized industrial control system, the wireless communication mode is replaced, which solves the problems caused by the traditional wiring mode. Wireless communication schemes mainly include GPRS / CDMA and wireless communication

　　There are two categories of line data transmission radio communication. At present, there are two kinds of wireless WAN in China: GPRS and CDMA. In different applications, the wireless transmission modes GPRS and CDMA networks are well established and maintained by China Mobile and China Unicom, so the operation cost is high and the initial investment is small, but there are blind spots, which are restrained by the operators. If you use the radio station, you can use it to build an overlay network. The frequency band has no interference, the operation cost is low, and the control system is simple It can be used in point - to - point and point - to - multipoint networks flexibly, without blind spots and being restrained by operators Suitable for use in a certain range. Digital radio is widely used in the construction of special network in the field of industrial control. The difference between digital radio and conventional transmission equipment is that it has been unattended for a long time, and the working environment is very complex. Many equipment are placed in the field, the power supply condition is unstable, and the temperature difference changes greatly. The equipment has strong anti-interference ability and good heat dissipation. It can adapt to long-term work in harsh environment and electromagnetic environment, and its working temperature range is wide.

　　The requirements for product structure, technical index and environmental index of data transmission radio station are much higher than those of conventional data transmission equipment. Compared with erecting special cables (or optical cables) and renting special telecommunication lines, it has the advantages of low cost, fast construction, reliable operation and simple maintenance. The project is located in the suburbs, and the coverage of China Unicom mobile signal is poor. If the cable is laid, it will pass through farmland and hardened pavement. The construction cost is high. The comprehensive site conditions and later operation cost are controlled by radio station and PLC.

　　2. System design

　　The project adopts long-distance wireless data transmission radio for communication transmission, which is composed of water source control box AP1 for controlling deep-water well pump, water tower control box ap2 for water supply signal acquisition and display control box AP3 in duty room. Each control box is composed of user equipment, wireless data transmission equipment and PLC.

　　2.2 control scheme

　　The water tower control box ap2 is responsible for collecting and processing the data of the side water level, water pressure, water tower upper pipe velocity and water tower lower pipe velocity of the water tower, and transmitting them to the water source control box AP1 and the display control box AP3; The water source control box AP1 is responsible for receiving the data of the water tower control box ap2 and the display control box AP3, controlling the start and stop of the deep-water well pump, and feeding back the operation parameters to the display control box AP3 and the fault indicator light: the display control box AP3 in the duty room is responsible for receiving and displaying the water level, water pressure, flow rate of the upper and lower pipes of the water tower control box ap2 and the API operation status and fault status data of the water source control box Be responsible for remote manual control of water pump operation.

　　If the remote / local switch of AP1 is in the local position, only the button AP1 of the water source control box controls the start and stop of the deep well pump. If the switch is in the remote position, the water level at the side of the water tower is less than h, the low water pump starts, and the water level is greater than h, and the high water pump stops. When the automatic / manual switch of control box AP3 is in the manual position, the water level, water pressure The flow rate of the upper and lower pipes is only displayed on AP3 and does not control the start and stop of the deep well pump The start and stop button on AP3 remotely controls the start and stop of deep well pump. If the contactor in the water source control box AP1 does not pull in, the pull in fault alarm will be fed back. If the motor does not rotate, the water pump has been damaged or the wiring fault alarm will be given. If the motor pulls in and the flow rate of the upper water pipe x the flow rate of the upper water pipe ≤ the flow rate of the lower water pipe x the diameter of the lower water pipe, the mechanical fault alarm of the water pump will be fed back. Thermal relay tripping feedback overload alarm. The poor communication of AP1, ap2 and AP3 is a communication fault, which is displayed on their respective control boxes. The system adopts distributed control to ensure high reliability; It is equipped with thermal fault and access control alarm to realize unattended duty; Built in watchdog function to detect whether the communication at each end is normal in real time In case of abnormality, the water pump will shut down automatically, with double sensing of water level and water pressure, so as to avoid overflow accident caused by out of control of the water pump.

　　2.3 performance parameters of the system:

　　(1) Working frequency: jy-rtu6640 series radio station can work at 220 ~ 240mhz conventional frequency.

　　(2) Physical interface: standard RS-232, communication rate 9600bps, completely transparent transmission, without special communication software.

　　(3) Working mode: full duplex

　　(4) Transmission distance: within 10 km.

　　(5) Power supply mode: when the radio works, the voltage is 12VDC, the transmitting current is 575ma (2W power, 13.8vdc), and the receiving current is 75ma. Equipped with switching regulated power supply for 220VAC operation.

　　(6) Working temperature: 45 ℃ ~ + 85 ~ C (refer to the communication report of temperature test of remote measurement and control terminal (RTU))

　　(7) Relative humidity: 95%, 40 ℃, no condensation.

　　3. Concluding remarks

　　The actual operation shows that the remote control system of water supply based on wireless data transmission radio station runs stably and achieves satisfactory results. The system can greatly reduce the labor intensity of operators and improve the working environment of operators. The equipment has the advantages of simple debugging, convenient operation, safe use, reliable operation, high efficiency and low failure rate, which realizes the centralized monitoring of the whole water supply system by the operator in the duty room. At the same time, due to the modular structure of software and hardware, it is convenient for engineers and technicians to install, debug and maintain, and can bring good social and economic benefits. Although this paper only takes jy-rtu6640 data transmission as an example to illustrate the construction, configuration and implementation process of this system, in fact, similar steps are adopted for PLC of other companies to realize the function of remote control.