Elevator, the necessary transportation tool for tall buildings, is used for transferring passengers and commodities vertically. Most traditional elevator control system adopts relay--- contacting machine as its central director. But this system has so many disadvantages such as too many contacting points, high fault rate, heavy repairing work and so on. So if it was replaced by the control system equipped with PLC, the problems will be solved much more easily.
This essay explains the application of PLC (Mitsubushi PLC) on elevator，by discussing the construction of elevator control system. It also illustrates the general design project, the design process and construction of the PLC control system for three-story buildings, listing the specific main circuit, trapezia control chart of elevator and repertoires. It also shows the construction of frame chart of the system and process flow chart. Thus the programming method of PLC is brought forward on the basis of analyzing and dealing with the logic relationship of random signs. It also designed a complicated elevator control system. If the project can be accepted, it can solve the problems which can be brought by relay, such as too many contacting points, high fault rate, low reliability, long installation and debugging time, heavy repairing work, complex connection and so on.
