Software offers configuration environment options

Configuration of programmable logic controllers is a common task in the controls industry because PLCs serve as the workhorse of automation in many industry segments from component manufacturing and assembly to chemical process automation. In each industry-specific requirements exist for each application, as well as individual preferences for programming methods.

06/01/2001


Configuration of programmable logic controllers is a common task in the controls industry because PLCs serve as the workhorse of automation in many industry segments from component manufacturing and assembly to chemical process automation. In each industry-specific requirements exist for each application, as well as individual preferences for programming methods.

There is also increasing use of third-party personnel (both internal and external) to perform initial programming. This can cause difficulties for individuals, who are called on to support these systems. Because of these variations in setup and among PLC programming environments, it can become increasingly difficult to implement required changes or locate operational errors later in the control system's lifecycle.

Expanded options

A package that assists with configuration in a vendor's product line is the Step 7 Micro/Win 32 from Siemens Energy & Automation, Inc. (Alpharetta, Ga.). The software supports programming of Siemens' S7-200 family of PLCs, and gives users a range of PLC capabilities to choose from while working in the same configuration environment.

Siemens' package covers a range of application sizes and is easy to work with, as well. When creating or editing a program, the user can select program elements by class from the toolbar or from the list of instructions on the left side of the display. Instruction choices are then explained in a context-sensitive Help menu, where functions and interconnects are described and illustrated. In addition, the software is shipped with a second CD, which contains electronic copies of all manuals for quick reference, as well "Tips & Tricks" application notes that aid typical projects.

When using toolbar objects, once a general class of operation is selected, a window is opened below the symbol on the network from which the specific operation desired can be selected. The list of instructions is also easy to comprehend because the user can select a "file" or type of instruction desired, which then expands to show all available instructions. The instruction list has an additional feature indicating which instructions are not supported by the current processor selection. This is important to note as the software does allow selection of an unsupported element. A program including an unsupported element will not compile for execution.

Freedom of choice

A unique feature of this package is the choice given to the developer. Any of three programming environments can be used. Prior to creating the first program line, users can select to work in traditional Relay Ladder Logic (RLL)—which is the default, Statement List Language (STL), or in Function Block Diagram (FBD). Each functions alike for instruction selection, but differs in the method of displaying the user program. Other development aids include "wizards" that assist with the setup of more complex tasks, such as PID loops and high-speed counters.

Once a program is complete and compiled without errors, users have the option of changing the programming environment. This allows programs to be developed in one environment and then supported in another, depending on user preference.

This review is based on version 3.1 of Step 7 Micro/Win 32 operating on Microsoft Windows 98. This package also runs on Windows 95/98 and NT.

For more information on Step 7 Micro/Win 32, Circle 345 online at www.controleng.com/freeinfo .

Tracy J. Coates P.E., contributing editor, is a consulting engineer at PCE Engineering (Johnson City, Tenn.)





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