Programmable Logic Controller PLC
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 devices connected as outputs.

Almost any production line, machine function or process can be automated using a PLC. The speed and accuracy of the operation can be greatly enhanced using this type of control system. But the biggest benefit in using a PLC is the ability to change and replicate the operation or process while collecting and communicating vital information.

A PLC consists of following main parts:

What is a PLC input/output?

PLC Operations consist of four steps

1. Input Scan: Scans the state of the Inputs
2. Program Scan: Executes the program logic
3. Output Scan: Energize/de-energize the outputs
4. Housekeeping

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Rockwell Automation AB -

SLC 500 Programmable Logic Controller

The SLC 500 family is a growing family of small programmable controllers built around two hardware options: a fixed controller or a modular controller. The modular controller offers you maximum flexibility in system configuration.  Wth its multiple processor choices, numerous power supply options and extensive I/O capacity, the modular SLC 500 controller allows you to create a system specifically designed for your application.

The fixed controller provides the power supply, inputs and outputs, and processor in one unit. It also offers a 2-slot expansion chassis for increased flexibility. The programming tools and most I/O modules are compatible between the two hardware options, so you can cost effectively solve a broad range of applications.

PLC-5 / 1771 Controller System

PLC-5 processors are available in a large range of forcible I/O (512 maximum through 3072 maximum) and maximum user memory (6K through 100K words). All are capable of controlling remotely-located I/O.  The maximum number of I/O locations ranges from 5 through 125.

A PLC-5 processor communicates across the 1771 backplane to 1771 I/O modules in the chassis in which the processor resides. A PLC-5 processor can communicate with I/O across a DeviceNet or Universal Remote I/O link. Selected models of PLC-5 processors can communicate with I/O across a ControlNet or Extended Local I/O link. I/O adapters for 1771 I/O are available for ControlNet, Universal Remote I/O, and Extended Local I/O links. General communication messages can be sent from or received by PLC-5 processors across DeviceNet, ControlNet, or Ethernet networks, as well as Data Highway Plus, RS-232-C, RS-422-A, or RS-423-A networks. You can add a DeviceNet port to any PLC-5 processor with a 1771-SDN scanner module. Each Ethernet PLC-5 processor has an on-board Ethernet port, and you can add an Ethernet port to any PLC-5 processor with a 1785-ENET Ethernet Interface Module.
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SLC 500 Processors

PLC-5 Family

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Simatic S7-300

Siemens Simatic PLC's -

Simatic S7

SIMATIC S7 lets you implement an array of different technologies with integrated solutions.

It is easy to parameterize functions in the TIA range, using the interactive screen forms embedded in STEP 7.

The STEP 7 basic package already includes blocks for control tasks. These blocks can be loaded onto any CPU. In the field of microautomation, STEP 7-Micro/WIN also offers a user-friendly assistant for programming technological functions.

For the count, measure, control and position processes, there are CPUs available featuring the technological functions as an integral part of the operating system.

The technological tasks are executed by way of the inputs and outputs directly integrated on the CPU.

The Technology CPUs 315T and 317T integrate performant PLCopen-certified technology and motion control functions right into the standard SIMATIC CPU.

Simatic ET200S

SIMATIC ET 200S is the distributed I/O station that guarantees lasting savings in life-cycle costs with the highest flexibility. Installation couldn't be easier and the bit-modular design of the ET 200S enables multifunctional use of the station.

The multifunctional ET200S can now communicate over PROFINET as well as over PROFIBUS, giving the proven and field-tested I/O station all the advantages of Ethernet communication. PROFIBUS-DP is the fastest, most standardised network at field level. It has been standardised in accordance with the European Norm EN 50170. PROFIBUS is completely integrated in the new SIMATIC world, both in terms of hardware and software.

Modules for the ET 200S include power modules, digital or analog input and output modules, technology modules and motor starters. The ET200S is also equipped for fail-safe signal modules and motor starters. Completely new is the ET 200S frequency converter, which makes it possible to perform variable-speed drive tasks for up to 4 kW power.

The SIMATIC ET 200 distributed I/O system makes it possible to connect digital and analog inputs/outputs with the central controller. ET 200 also allows to use intelligent I/O modules in distributed configurations.

Terminal modules with FastConnect technology that needs no stripping of cables help minimize rewiring time.

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Simatic ET200

The following support materials are available as free downloads in PDF format from the PLC website

PLC Primer ( 252K PDF file)
For those new to PLCs--Grasp the basics of PLCs

Programming and Documentation Pads (ALL) (720K PDF file)
These useful PLC listing pads allow you to implement better PLC design implementations and keep an orderly documentation system. Select a PDF with all listing and sample pads or individual listings with samples (below)

PLC Program Listing (184K PDF file)
Input/Output Listing (200K PDF file)
Register-Word/Internal Output Usage Listing (196K PDF file)
PLC Automation Project Notes (168K PDF file)

PLC Glossary of Terms (92K PDF file)
A complete glossary of the most often used terms in PLC systems

Logic Symbols, Truth Tables and Equivalent Ladder/PLC Logic Diagrams (20K PDF file)
Handy table of equivalent electromechanical ladder diagram and PLC symbols

Electrical Relay Diagram and P&ID Symbols  (88K PDF file)
Reference table of relay and P&ID diagram symbols used in design

What is PLC Ladder Logic?
Electrical Equipment and Components 
Free PLC Programming Tutorial and Examples
Web site contains general information about PLC Command Instructions and explains how they function in your application program. These Commands are based on Allen Bradley's SLC-500 PLC and their RSLogix-500 Software.

Each of the command instructions include information on:
- Specifications for the instruction
- How to use the instruction
- An example program application
Industrial Automation
Siemens PLC Training - Step 7

Siemens PLC Training - PCS 7

Siemens Simatic HMI WinCC

Siemens Simatic Hardware and Software Configuration

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