Wednesday, July 6, 2011

Micro Programmable Logic Controllers of Modicon





A PLC (Programmable Logic Controller) is a device of solid-state with the capabilities of digital processing designed for industrial real time control and applications of manufacturing. A PLC contains the units of input and output (I/O) and a CPU. The Modicon Micro PLCs are permanent I/O devices. The components of input and output are developed into the same physical box with the CPU. The package offers a light-weight, small, self-contained, and low-cost solution for a large range of control applications.

Theory of Operation
The major components of a Micro PLC monitors the field devices state by receiving signals from its inputs, resolves a user logic program saved in its CPU, and next directs added field device activity by transferring control signals to its outputs.

Inputs
The inputs are placed in a block of terminal across the top of PLC. Inputs are field-wired to devices of sensing in the appliance for example thumbwheels, pushbuttons, selector switches, limit switches, or motor starter contacts. If an input mind that an area sensor is closed, the input changes the voltage of field to a signal of logic-level understood by the CPU that explains the state of the sensor—a logic 1 designates a CLOSED state or ON, and a logic 0 designates an OPEN state or OFF.

CPU
Inside the CPU are the power supply, digital processor, and memory. These parts interrelate to resolve logic function and pass control signals to the outputs. The CPU interprets the transformed input data, performs the user logic program saved in its memory, and next writes the suitable output signals to the switching devices area. The reading input signals process, work out logic based on the inputs states, and next updating the output machines is namely scanning.

Flash Memory
Also enclosed in the CPU is a component of Flash Memory where the PLC’s operating system exists in. The Flash contents are nonvolatile—they do not need backup of battery. The operating system inhabit in Flash is a supervisory programs of collection that give the PLC its self by: Defining the language in which the function program is written—i.e., ladder logic Assign the resources of CPU’s memory for definite purposes formative the structure in which the PLC saves and handles data The operating system of ladder logic describes the Modicon Micro PLCs functional capabilities.

Outputs
The outputs are placed in the block terminal of crossways the PLC bottom. Outputs turn the voltage of supplied control that energizes or de-energizes the area switching areas in your application. If an output is switched ON by the CPU, the voltage control is controlled to activate the addressed device.



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