该文介绍了用PLC改造旧设备时,根据原继电器电路图设计梯形图的方法与步骤,并针对具体应用中存在的问题,给出了解决方法及注意事项。PLC是以微机技术为基础发展起来的新一代工业控制装置,目前它已被广泛应用于各个领域。它是把继电器控制的优点与计算机的功能齐全、灵活性、通用性相结合,用计算机编程软件逻辑代替了继电器接线逻辑的一种通用性自动控制设备。目前,用PLC控制取代继电器控制已是大势所趋。有些 This paper introduces the method and steps of designing the ladder diagram according to the original relay circuit diagram when transforming the old equipment with PLC, and gives the solutions and precautions for the problems in the specific application. PLC is a new generation of industrial control device developed on the basis of microcomputer technology. At present, it has been widely used in various fields. It is the relay control of the advantages of computer functions, flexibility, versatility combined with computer programming software logic instead of the relay wiring logic of a universal automatic control equipment. At present, using PLC control to replace the relay control is the trend of the times. some