1. System composition and communication methods between devices

1.1 System composition

The system consists of Kunlun Tongshi TPC7063E touch screen, Siemens S7-300 module, TRICONEX 3674, and PCAdapter for data conversion between the two. TPC7063E not only has the ability to interact with numerous hardware, but also conveniently read and write data from various industrial control devices such as PLCs, intelligent instruments, intelligent modules, and frequency converters. It also has powerful network communication capabilities, supporting serial communication and Ethernet communication methods. The Siemens S7-300 module is used to complete data acquisition, processing, and input/output control functions. The PC adapter converts the MPI communication signal into an RS232 serial port signal, thereby completing the MPI data communication function.

1.2 Communication method between touch screen and PLC

The touch screen adopts MPI communication mode with the S7 300 PLC.

MPI, short for Multi Point Interface, 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 speed is not high and the communication data volume is not large. The communication speed of MPI network is 19.2 Kbps~12 Mbps, and it can connect up to 32 nodes. The MPI network has a network number, and before building the MPI network, each node needs to be assigned an MPI address and one highest MPI address, so that all nodes connected through MPI can communicate with each other. PLC establishes communication with touch screen TP7063E through this interface. The user interface of STEP7 provides communication configuration functions, making communication configuration relatively simple.

The MCGS embedded configuration software supports TPC7063E touch screens. The S7300_400MPI component provided inside is used by MCGS software to read and write various registers of Siemens S7-300/400 series PLC equipment through an MPI adapter. The driver type is a serial sub device, which must be connected to a “universal serial parent device” to work. The communication protocol is MPI, and the communication method is one master and one slave communication. The driving components are the main components, and the PLC equipment is from.

1.3 System Design and Verification

In order to verify the reliability of the system operation, we have designed a control system. It consists of three parts,

① Field level equipment. Including temperature, pressure, water level sensors, and water pump operation control cabinet;

② PLC processing level equipment. They complete data downloading, processing, and communication functions, mainly including power module 1, CPU module 2, Ethernet module 3, and analog module 4;

③ Management level devices. Mainly using Kunlun’s TPC7063E touch screen, responsible for monitoring and controlling on-site equipment data.

The overall structure of the system is shown in Figure 1.

 

The control system scheme requires the following basic functions to be achieved through MPI communication between S7-300PLC and Kunlun TPC7063E touch screen:

(1) The instrument on the touch screen can display temperature, pressure, and water level values;

(2) Control the water pump by operating the open and close valve commands on the touch screen;

(3) By operating the start stop button, the touch screen can accurately reflect the changes at each point;

(4) Enter 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 it to correctly display the year, month, day, hour, minute, and second.