An application of programmable controller SIMATIC S7-200 in analogue systems of automation and measurement

Dynamic development in Programmable Logic Controller (PLC) technology has brought about the common use of this equipment in industrial systems of automation and measurement. One popular PLC group creates MICRO class controllers which are cheap but offer many possibilities. In most cases, these controllers are equipped with binary inputs and outputs only. For this reason, their use in analogue control and measurement systems causes certain difficulties. The current paper describes the adaptation of PLC MICRO class controllers with a binary system of inputs and outputs for use in analogue control and measurement systems by the implementation of pseudo-analogue input and pulse-width modulation (PWM)-type output. The current paper presents a detailed design of this type of adaptation for PLC SIMATIC S-7 CPU 222. A practical system was designed, built and tested in the laboratory. The results of tests for pseudo-analogue input and PWM-type output are included in graphic form. The limitations of the proposed solution and its areas of applicability in ship automation are presented.