The strategy of PLC implementation for a control task closely follows the development of an algorithm. The user has to implement the control from a set of basic instructions and produce the solution in a finite number of steps. If developing an algorithm to solve the problem becomes difficult, he or she needs to return to task definition to redefine the problem. We can not develop a control strategy until we have all of this information of problem definition.
A programmable controller or PLC is a powerful machine, but it can only do what it is told to do. It receives all of its directions from the control program, the instruction set or solution algorithms created by the programmer. Therefore, a PLC success control program depends on how organized the user is. There are many ways to approach a problem, but if the application is approached in a systematic manner, the probability of mistakes is less.
The techniques used to implement the program of control vary according to the programmer. The programmer should follow certain guidelines. New applications are new systems, while modernizations are upgraded to existing control systems that have functioned previously without a PLC, through electromechanical control or individual, loop controllers, analogue.
Understanding the machine or process operation is the first step in a systematic approach to solving the control problem as mentioned previously. The strategy should follow the problem definition for new applications. Reviewing of strategies for new applications as well as revising the control actual method for a modernizing project, will help detect errors that were introduced during the planning stages.
The programming stages reveal the difference between modernization and new projects. The users already understand the operation of the machine or process in a modernization project along with the control task. An existing relay ladder diagram usually defines the sequence of events in the control program. This ladder diagram can be almost translated directly into PLC ladder diagrams.