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After the CPU processes the input data (input scan), it will then make any needed output changes after executing the user program (output scan). There are four basic steps in the operation of all PLCs: Input Scan, Program Scan, Output Scan, and Housekeeping. These steps continually take place in a repeating loop.
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associated high cost of these systems propagated a need for a less costly alternative. In recent years, the equipment used in the manufacture of glass has become more sophisticated, further increasing the demand for PLC solutions that are based on a DCS, which in turn is driving the demand for technicians who have completed PLC programming courses.
and impact. A PLC will consist of two basic sections: the central processing unit (CPU) and the Input/Output (I/O) interface system. The CPU controls all system activity primarily through its processor and memory system. The CPU consists of a microprocessor, memory chip and other integrated circuits to control logic, monitoring and communications.
Basic PLC Operation. PLCs consist of input modules or points, a Central Processing Unit (CPU), and output modules or points. An input accepts a variety of digital or analog signals from various field devices (sensors) and converts them into a logic signal that can be used by the CPU.
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• Describe important number systems and data types used by Siemens PLCs. • Identify the major components of a PLC and describe their functions. • Describe the parts of a typical PLC scan. • Define the terms “functional safety” and “failsafe.” • Identify the key features of S7-1200 standard and failsafe CPU models.
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The processor of a PLC (Courtesy: Allen-Bradley) The main processor (or CPU) is a microprocessor-based system that executes the control program, after reading the status of the field inputs. It, in turn, sends commands to the field outputs. Depending on the manufacturer, it is possible to find bit or word processors.
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Welcome. The Programmable sequential relay circuits electronic which are. Almost any fact, whether assembly, Controllers, covers or PLCs. Controller (PLC) was in machine controls ogic the functions, operation memory, via. application that machining, packaging, industries, FIGURE 1: A PROGRAMMABLE LOGIC CONTROLLER.
