Development And Realization Of Comprehensive PLC Experimental System

Due to experimental teaching estalishments, equipment, funds, and many other objective conditions and restrictions, it is too difficult to equip real control object in laboratory, leading to non-intuitive experimental results. To solve the problems above mentioned, this paper has developed a set of full-featured PLC experimental teaching device which can dynamically display the work status of the system and improve the experimental efficiency greatly.PLC integrated experimental system consists of the controlled object simulation software on computer and I/O interface circuit. In this paper, the basic structure and working principle of the PLC experimental system are discussed, then analyzes the correlative software and hardware technologies as well as the development methods, besides, MCU interface, USB communication and computer simulation technology used in the system's specific design are elaborated.Sencondly, the hardware of PLC experimental system is designed centering on USB-C8051F340 microcontroller for the PLC digital and analog input/output signal process, completed the data transmission between the PLC and its controlled device model. Aiming at the specific functional requirements of the PLC experimental system, the MCU firmware is developed in C language to deal with USB bus protocol which achieved the data transfer between MCU and PC.Thirdly, with the methods of Windows operating system I/O device driver principle and the dynamic link library technology, USB communication programme is developed using Visual C++. Through calling the DLL in Labview platform, the communication of computer with MCU is realized, writing PLC's digital/anolog input signal and reading its output signal regularly. Then Labview is used to build PLC controlled device simulation model, realized the dynamic display of its actual running status.Finally, five sequential control system experiments are explored. The results show that PLC intergrated experimental system can fulfill the teaching requirements with friendly interface, the effect and efficiency of experiments are also improved.