With the continuous development of industrial technology, automatic control has gradually been taken seriously and started to be applied in factory production, which has led to the unprecedented development of automatic control technology to replace people engaged in dangerous and repetitive production work. Since programmable controllers have the advantages of high safety, a low market price, perfect functions, and easy maintenance, they are extremely widely used in modern industry. According to the design requirements, this paper uses the S7 series PLC in the small machine developed and produced by Siemens Germany and focuses on its features and functions. This paper takes the inner bearing spray washing machine of a railroad wagon locomotive as the object, designs the electrical control schematic and PLC control program, which can realize fully automatic control washing and at the same time has the power-down protection function, and can realize automatic-checking conversion operation and manual setting of spray washing time.
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