O module be merged into this article. They were first developed in the automobile manufacturing industry to provide flexible, ruggedized and easily programmable controllers programmable logic controllers frank d. petruzella pdf download replace hard-wired relays, timers and sequencers.
Did not find what they wanted? Try here
Since then they have been widely adopted as high-reliability automation controllers suitable for harsh environments. O, and which are often networked to other PLC and SCADA systems. O, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory. It was from the automotive industry in the USA that the PLC was born. Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was mainly composed of relays, cam timers, drum sequencers, and dedicated closed-loop controllers.
When digital computers became available, being general-purpose programmable devices, they were soon applied to control sequential and combinatorial logic in industrial processes. However these early computers required specialist programmers and stringent operating environmental control for temperature, cleanliness, and power quality. To meet these challenges the PLC was developed with several key attributes. One of the people who worked on that project was Dick Morley, who is considered to be the “father” of the PLC. One of the very first 084 models built is now on display at Schneider Electric’s facility in North Andover, Massachusetts. It was presented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service.
Modicon used the 84 moniker at the end of its product range until the 984 made its appearance. The automotive industry is still one of the largest users of PLCs. In a parallel development Odo Josef Struger is sometimes known as the “father of the programmable logic controller” as well. Early PLCs were designed to replace relay logic systems. These PLCs were programmed in “ladder logic”, which strongly resembles a schematic diagram of relay logic.