Programmable Logic Controllers Basic Level

The programmable logic controller represents a key factor in industrial automation. Its use permits flexible adaptation to varying processes as well as rapid fault finding and error elimination. This textbook explains the design of a programmable logic controller and its interaction with peripherals. One of the main focal points of the textbook deals with the new international standard for PLC programming, the EN 61131-3 (IEC-61131-3). This standard takes into account expansions and developments, for which no standardised language elements existed hitherto. The aim of this new standard is to standardise the design, functionality and the programming of a PLC in such a way as to enable the user to easily operate with different systems. In the interest of continual further improvement, all readers of this book are invited to make contributions by way suggestions, ideas and constructive criticism….

The PLC in automation technology 1.1 Introduction The first Programmable Logic Controller (PLC) was developed by a group of engineers at General Motors in 1968, when the company were looking for an alternative to replace complex relay control systems. The new control system had to meet the following requirements: * Simple programming * Program changes without system intervention (no internal rewiring) * Smaller, cheaper and more reliable than corresponding relay control systems * Simple, low cost maintenance Subsequent development resulted in a system, which enabled the simple connection of binary signals. The requirements as to how these signals were to be connected were specified in the control program. With the new systems it became possible for the first time to plot signals on a screen and to file these in electronic memories. Since then, three decades have passed, during which the enormous progress made in the development of microelectronics did not stop short of programmable logic controllers….

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