What is a Programmable Logic Controller (PLC)?
Automation of many different processes, such as controlling machines or factory assembly lines, is done through the use of small computers called a programmable logic controller (PLC). This is actually a control device that consists of a programmable microprocessor, and is programmed using a specialized computer language. Before, a programmable logic controller would have been programmed in ladder logic, which is similar to a schematic of relay logic. A modern programmabl logic controller is usually programmed in any one of several languages, ranging from ladder logic to Basic or C. Typically, the program is written in a development environment on a personal computer (PC), and then is downloaded onto the programmable logic controller directly through a cable connection. The program is stored in the programmable logic controller in non-volatile memory. Programmable logic controllers contain a variable number of Input/Output (I/O) ports, and are typically Reduced Instruction Set Computer
Many years before the PLC was invented, machine controllers used combinational circuits, like a combination of many relays, timers or any other devices, mechanical controller like cam shafts and drums, including electronic circuits to make a sequence process (logic control system). With this old sequential controller, the circuit looks very crowded and usually it’s hard to find the malfunctioning part, or to even modify the sequence, also requires more time and cost. The old sequential controller was implemented only in small scale or medium scale systems and was specific to a system or machine. Because in large scale systems, it is hard to test the ability and the efficiency of the entire system. This system also cannot be implemented in the process that needs a high speed control. So that’s why the PLC was invented. Many new industries have already implemented PLC systems to control their machines. PLC is operated by the instruction input from the input devices (like push button swit
A PROGRAMMABLE LOGIC CONTROLLER (PLC) is an industrial computer control system that continuously monitors the state of input devices and makes decisions based upon a custom program to control the state of output devices. Almost any production line, machine function, or process can be greatly enhanced using this type of control system. However, the biggest benefit in using a PLC is the ability to change and replicate the operation or process while collecting and communicating vital information. Another advantage of a PLC system is that it is modular. That is, you can mix and match the types of Input and Output devices to best suit your application.
Chapter 2: Understanding the Input/Output (I/O) Section. Chapter 3: Processor Unit. Chapter 4: Programming Devices (Programmers). Chapter 5: Memory Organization. Chapter 6: Numbering Systems. Chapter 7: Understanding and Using Ladder Diagrams. Chapter 8: Relay Type Instructions. Chapter 9: Programming a PLC. Chapter 10: Programming Considerations. Chapter 11: Program Control Instructions. Chapter 12: Programming Timers. Chapter 13: Programming Counters. Chapter 14: Data Manipulation. Chapter 15: Math Functions. Chapter 16: Word and File Moves. Chapter 17: Sequencers. Chapter 18: Process Control Signals, Scaling, and PID introduction. Chapter 19: Programming with Boolean. Chapter 20: Understanding Communictaion Networks. Chapter 21: Start Up and Troubleshooting. Chapter 22: PLC Programming Examples. Glossary. Index. About the Authors: Richard A. Cox is the Executive Director of COXCO Training and Consulting in Spokane Washington and is a retired member of the Electrical, Robotics Depart
Many-many years before PLC was infented, machine controllers using a combinational circuits, like combine of many relays, timers or any other devices, mechanical controller like cams shaft and drums, include of electronics circuits to made a sequence process (logic control system). With this old sequensial controller, the circuit looks very crowded and usually it is hard to find the malfunction part, or even to modify the sequence, besides that it needs more time and cost too. The old sequensial controller also implemented only in small scale or medium scale system and specific to a system or machine, because in large scale system, it is hard to test the ability and the efficiency of the entire system. This system also cannot implemented in the process that needs a high speed control. So thats why the PLC was infented. Many new industries now a day already implemented PLC systems to control their machines. PLC is operated by the instruction input from the input devices (like push butto
