Programmable logic controllers (PLCs) automate electromechanical processes using a microprocessor programmed in a specialized language. They monitor sensor inputs and control output actuators, replacing thousands of relays and timers. PLCs have a range of functionality and can withstand harsh environments. They can be configured with various interfaces and were first developed for the automotive industry in 1968.
Automation of many electromechanical processes, such as the movement of machinery on an assembly line, is done through the use of small computers called programmable logic controllers (PLCs). A PLC contains a programmable microprocessor that is programmed using a specialized computer language. Typically, the program for the automated process is written to a computer and then downloaded directly to the programmable logic controller via a cable connection. The program is stored in the programmable logic controller in non-volatile memory.
Inputs and outputs
Programmable logic controllers typically contain a variable number of input/output (I/O) ports and typically use reduced instruction set computation (RISC), which consists of simplified instructions that are intended to allow for faster. PLCs are designed for real-time use and often have to withstand harsh factory environments, such as excessive vibration and high noise levels. The programmable logic controller circuit monitors the state of multiple sensor inputs, which control output actuators such as motor starters, solenoids, lights, displays, and valves.
Advantages
This type of controller has made significant contributions to factory automation. Previous automation systems had to use thousands of individual relays, timers and sequencers, which had to be replaced or rewired every time the automated process needed to change. In many cases, a programmable logic controller allows you to replace all relays and timers within a factory system with a single controller. Modern PLCs offer a wide range of functionality including basic relay control, motion control, process control and complex networks. They can also be used in a distributed control system (DCS).
interfaces
There are several types of interfaces that are used when people need to interact with programmable logic controllers to configure or work with them. The interface could be configured with simple lights or switches, or it could include a text display. A more complex system might use an Internet-based interface to a computer running a supervisory control and data acquisition (SCADA) system.
History
PLCs were initially created to serve the automotive industry. The first programmable logic controller design was developed in 1968 for General Motors to replace hardwired relay systems with electronic controllers. PLCs remained in widespread use into the early 21st century in manufacturing sectors such as the automotive industry.
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