Abstract: This paper introduces a multi-story elevator control system developed using an AC variable frequency speed control method, with an FX2N-80MR PLC as the main controller and an N2-420 frequency converter as the N2-420. The following problems were solved through program design and debugging: remote speed control; directional and leveling control; door control; and digital control of internal commands and external call signals. Keywords: elevator; PLC; ladder diagram; collective control; frequency converter 0 Introduction A PLC is an industrial control device with a microprocessor as its core. It combines traditional relay control systems with computer technology, featuring high reliability, flexibility, ease of programming, and convenient use. The collective control system, composed of a PLC and variable frequency speed control, can better meet the control requirements of elevators, a mechatronic device with random control and complex logical relationships. 1 Basic Structure and Control Requirements This elevator is a ten-story elevator, 30m high, with each floor 2.8m high. Its electrical control system consists of a PLC, frequency converter, traction motor, door motor, safety devices, hoistway system, car control panel, hall control box, and floor indicators. The main control requirements of the system are as follows: ① Automatic door opening and closing; ② Registration, cancellation, and display of internal commands and external call signals; ③ Orientation; ④ Automatic floor selection; ⑤ Indication of the car's arrival floor position; ⑥ Pre-deceleration during leveling and automatic door opening upon stopping at level; ⑦ Forced speed change at the terminal station. [b][align=center]For details, please click: Design of an Elevator Control System Based on PLC[/align][/b]