Design and Implementation PLC Real-Time Control Based on NI-VISA

Abstract

PLC is an industry control computer which applies microprocessor to its core PLC has been applied to the distributed monitor system which is responsible for high speed data collect of the spot, logic operation, count, PID regulate etc. The computer has been used to manage the monitor system. The HostLink communication protocol of OMRON CP series PLC is introduced in this paper. This article introduces the serial communication control VISA provided by the LabVIEW, the command of the programmable operation of PLC, the link method between PC and PLC, the communication parameters setup of PLC.The article also introduces how to use the RS-232 serial communication port to realize the communication between PC and PLC. The method for realizing the communication between PLC and the host computer is presented by means of LabVIEW. The communication procedure and program is also introduced in detail in the paper. This method ensures that the communication is real time and accurate. Through reading and writing of the host computer from or to the PLC, automatic collection of field data is realized, and the device can be monitored and controlled effectively. The serial communication software is proved to be reliable and stable through the successful application in actual project. This article discusses the communication method between PC and PLC and the structure of s oft and hardware, applying the visual program language. The method can make the best of resources and characters of the system and improve communication efficiency.