The Step 7 Lite is a new product for automation programming in the established Simatic Step 7 line of IDEs. The system supports programming of several Siemens product lines of S7 300, ET200S ET200X series, comprising comparatively simple PLC components. It is intended for less or more basic problems at the lower end of the range of PLC applications. Siemens hopes that a highly usable and innovative product will help it gain access to new markets internationally.
PLC programming at nearly all existing IDEs for have a very long learning curve. The slow features accretion of implemented by diverse teams at various times, and the consistency resulting lack among the various subsystems have added to difficulties in learning and mastery and to complications in use. Functionality and features have been the driving forces in PLC programming tools with relatively little attention paid to usability during design. Moreover, the roles of actual users and the detailed nature of their tasks have not been articulated fully to be reflected in user interface design.
The key performance issues driving the Step 7 Lite system design were: immediate usability by qualified but inexperienced users, flexible accommodation to a wide range of work styles and reduction of user errors, programming practices, closer fit between the user interface, increases in productivity through reduced user steps as well as reduced errors, and the way actual PLC programmers think and work, and tasks implification where consistent with the need for great flexibility and with recognition of the inherent complexity and unpredictability of the PLC programming process.
This last point bears emphasis, as it makes the problem unusual in the application of a performance- centered design philosophy. No step-by-step process template or other rigidly structured performance would be acceptable within this kind of application or by the targeted users.