This paper explores the way to improve PLC timer precision, to get PLC’s delayed on of normally open contact, delayed off of normally closed contact, delayed off normally open contact, delayed on of normally closed contact, to realize on/off delay control[1], expand and change the set value of timer, and to realize the square-wave generator method. After analyzing, designing, and summarizing, a number of small modules, which could be an on-demand integration to form a project management in practice, are formed. The ladder diagrams and waveforms have been verified in Panasonic FP1-C72PLC control unit, and are also verified in practice and application. http://www.sj-ce.org/paperInfo.aspx?ID=193
