Scheme to realize data communication between touch screen and PLC
1 System composition and communication method between devices 1.1 System composition The system consists of Kunlun TPC7063E touch screen, Siemens S7-300 module, and PCAdapter for data conversion between the two. TPC7063E not only has the function of interacting with many hardware, it can easily read and write the data of various PLC, intelligent instruments, intelligent modules, inverters and other industrial control equipment, but also has a powerful network communication function, supports serial communication and Ethernet communication . Siemens S7-300 module is used to complete data acquisition, processing and input and output control functions. The PC Adapter completes the conversion of MPI communication signals to RS232 serial signals to complete the MPI data communication function. 1.2 Communication method between touch screen and PLC The MPI communication method is adopted between the touch screen and S7 300PLC. MPI is the abbreviation of Multi-Point Interface (MulTI Point Interface). It is a confidential protocol developed by Siemens for communication between PLCs . Its physical layer is RS-485. MPI communication is a simple and economical communication method that can be used when the communication rate is not high and the amount of communication data is not large. The communication rate of the MPI network is 19.2 Kbps ~ 12 Mbps, and a maximum of 32 nodes can be connected. The MPI network has a network number. Before forming an MPI network, each node must be assigned an MPI address and a highest MPI address, so that all nodes connected through MPI can communicate with each other. The PLC establishes communication with the touch screen TP7063E through this interface. The user interface of STEP7 provides the communication configuration function, which makes the configuration of communication relatively simple. MCGS embedded version configuration software supports TPC7063E touch screen. The provided S7300_400MPI component is used by MCGS software to read and write various registers of Siemens S7-300 / 400 series PLC devices through the MPI adapter. The driver type is a serial port sub-device, which must be connected to the "universal serial port parent device" to work. The communication protocol is MPI, and the communication mode is a master-slave command mode. The driving component is the main, and the PLC device is the subordinate. 1.3 System design and verification In order to verify the reliability of the system operation, we designed a control system. It consists of 3 parts, â‘ Field-level equipment. Including temperature, pressure, water level sensors and pump operation control cabinet; â‘¡PLC processing level equipment. They complete data download, processing and communication functions, including power module 1, CPU module 2, Ethernet module 3 and analog module 4; â‘¢ Management level equipment. Mainly adopts Kunlun TPC7063E touch screen, which is mainly responsible for field-level device data monitoring and control. The overall structure of the system is shown in Figure 1. Through MPI communication between S7-300PLC and Kunlun TPC7063E touch screen, the control system solution requires the following basic functions: (1) The meter on the touch screen can display temperature, pressure, and water level values; (2) Control the pump by operating the valve opening and closing commands on the touch screen; (3) By operating the start and stop buttons, the touch screen can correctly reflect the changes of various points; (4) Input the set water level value on the touch screen, if it exceeds the set water level, turn on the pump, otherwise turn off the pump; (5) You can set the system time and start the time so that the year, month, day, hour, minute, and second are displayed correctly.
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