PLC Overview PDF
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This document provides an overview of Programmable Logic Controllers (PLCs). It discusses their applications in industrial processes, highlighting their advantages over traditional relay control systems. The text emphasizes features like reliability, flexibility, ease of troubleshooting, and cost-effectiveness, along with communications capabilities and quick response time. The document also touches on the basics of computer architecture underlying PLC design.
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# Programmable Logic Controllers (PLCs) ## An Overview ### 1.1 Programmable Logic Controllers ### 1.1.1 PLC Overview Programmable logic controllers are now the most widely used industrial process control technology. A PLC is basically a digital computer designed for use in machine control. It h...
# Programmable Logic Controllers (PLCs) ## An Overview ### 1.1 Programmable Logic Controllers ### 1.1.1 PLC Overview Programmable logic controllers are now the most widely used industrial process control technology. A PLC is basically a digital computer designed for use in machine control. It has been designed to operate in the industrial environment and is equipped with special input/output interfaces and a control programming language. Initially, the PLC was used to replace relay logic, but its ever-increasing range of functions includes timing, counting, calculating, comparing, and the processing of analog signals. The structure of a PLC is based on the same principles as those employed in computer architecture. ## Programmable Logic Controller Advantages ### Advantages: * **Elimination of much of the hardwiring associated with conventional relay control circuits.** Relay panels are shown with extensive hard wiring. PLC control panels utilize less wiring. * **Increased Reliability** - Since all the logic is contained in the PLC’s memory, there is no chance of making a logic wiring error. * **More Flexibility** - It is easier to create and change a program in a PLC than to wire and rewire a circuit. * **Lower Cost** - Generally, if an application has more than about a half dozen control relays, it will probably be less expensive to install a PLC. ### Capabilities: * **Communications Capability** - A PLC can communicate with other controllers or computer equipment to perform such functions as supervisory control, data gathering, monitoring devices and process parameters, and download and upload of programs. * **Faster Response Time** - Machines that process thousands of items per second and objects that spend only a fraction of a second in front of a sensor require the PLC's quick-response capability. * **Easier to Troubleshoot** - To find and fix problems, users can display the control program on a monitor and watch it in real time as it executes
