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.
