Abstract : This paper describes the automatic control of an elevator using a Siemens S7-200 series programmable controller CPU226CN as the control core, expanded with an EM223CN expansion module, and a Siemens MM440CN frequency converter as the motor drive. The output is achieved through a traction machine. The main functions of the elevator include: responding to internal and external call signals, automatic door opening and closing, automatic leveling, and automatic display of the car position (floor). A novel design concept and approach were adopted, resulting in significant technological breakthroughs. Multiple input signals are input to the PLC input terminal through an OR gate, and the PLC's internal logic unit filters the signals, saving I/O ports and significantly reducing hardware design costs. The elevator features smooth and comfortable lifting, safe and reliable operation. Keywords : elevator; PLC; CPU226CN; MM440 An elevator is a general term for vertically running elevators (usually referred to as elevators), inclined escalators, and inclined or horizontal moving walkways. Elevators have become a widely used means of passenger transportation in modern life. The continuous pursuit of elevator safety, efficiency, and comfort has driven the advancement of elevator technology. Currently, the method of using programmable logic controllers (PLCs) to replace microcomputers for signal selection control gives elevator control systems high reliability, convenient and flexible programming, strong anti-interference capabilities, and stable operation. Therefore, various elevator control systems now widely adopt PLCs. Achieving low-cost, high-performance elevator control is therefore particularly important. 1. Elevator Control System Design 1.1 Hardware Composition The key to controlling passenger elevators with PLCs is how to rationally utilize the PLC's hardware resources, save on PLC input/output ports, and reduce design costs; at the same time, fully utilize software resources to simplify the control program, shorten the PLC's scan cycle, and improve the elevator's safety, reliability, and operational flexibility; furthermore, the control program should be as simple as possible and have certain regularity, suitable for developing control requirements for various floors. The following analysis uses a 5-story passenger elevator as an example to illustrate the system design approach. The PLC control unit is the core of the elevator control system. The main unit uses a Siemens 7-200 series programmable controller CPU226CN (24 inputs/16 outputs), and a Siemens MM440CN frequency converter is used as the motor drive. The system block diagram is shown in Figure 1. The PLC provides the frequency converter with the running direction and speed commands, enabling the frequency converter to adjust the running direction and speed according to the elevator's required speed curve. Through proper PLC programming, collective control functions such as automatic leveling, automatic door opening and closing, automatic stop time monitoring, registration and cancellation of internal and external call signals, forward-direction elevator stop, and automatic reversing are achieved. [Full text available for download: Application of PLC Technology in Elevator Operation]