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What Is A Programmable Logic Controller (PLC)?
What Is A PLS?
What Is A Programmable Logic Controller (PLC)?
Stepper vs Servo
A PROGRAMMABLE LOGIC CONTROLLER (PLC) (PLC) is an industrial computer control system that continuously monitors the state of input devices and makes de cisions based upon a custom program to control the state of output devices.
What Is A Stepper Motor? Stepper Drivers: RMS vs Peak C urr urrent? ent? What Is A PLC? Press Releases
What Is A PLC?
Almost any production line, m achine function, function, or process pro cess can be greatly enhanced using this type of control system . Howe ver, the the biggest benefit in using a PLC is the ability to change and replicate the operation or process while collecting and communicating vital information. Another advantage of a PLC system is that it is m odular. odular. That is, you can m ix and match the types of I nput and Output Output devices to best suit your application. History of PLCs
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Also Also see o ur line line of P LC Modules; we carry Allen-Bradley, Allen-Bradley, GE Fanuc Series, Series, and M odicon:
The first Programmable Logic Controllers were designed and developed by Modicon as a relay re-placer for GM and Landis. These controllers eliminated the need for rewiring and adding additional hardware for each new configuration of logic. The new system dra stically increased the functionality functionality of the controls while reducing the cabinet space that housed the logic. The first PLC, model 084, was invented by Dick Morley in 1969 The first commer cial successful successful PLC, the 184, was introduced in 1973 1973 and was designed by Michael Greenberg. What Is Inside A PLC?
PLC Mo dules dules Allen-Bradley GE Fanuc Series Modicon
The Central Processing Unit, the CPU, contains an internal program that tells the PLC how to perform the following functions: Execute the Control Instructions contained in the User's Programs. This program is stored in "nonvolatile" memory, meaning that the program will not be lost if power is removed Communicate with other devices, which can include I/O Devices, Programming Devices, Networks, and even other PLCs. Perform Housekeeping activities such as Communications, Internal Diagnostics, etc. How Does A PLC Operate? 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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AMCI : Tech Tutorials : What Is A Programmable Logic Controll er (PLC)? http://www.amci.com/tutorials/tutorials-what-is-programmable-logic-co...
Four Steps In The PLC Operations 1.) Input Scan Detects the state of al l input devices that are connected to the PLC 2.) Program Scan Executes the user created program logic 3.) Output Scan Energizes or de-energize all output devices that are connected to the PLC. 4.) Housekeeping This step includes comm unications with programming terminals, internal diagnostics, etc...
These steps are continually processed in a loop.
What Programming Language Is Used To Program A PLC? While Ladder Logic is the most commonly used PLC programming language, it is not the only one. The following table lists of some of languages that are used to program a PLC. Ladder Diagram (LD) Traditional ladder logic is graphical programming language. Initially programmed with simple contacts that simulated the opening and closing of relays, Ladder Logic programming has been expanded to include such functions as counters, timers, shift registers, and math operations.
Function Block Diagram (FBD) - A graphical language for depicting signal and data flows through re-usable function blocks. FBD is very useful for ex pressing the interconnection of control system algorithms and logic.
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AMCI : Tech Tutorials : What Is A Programmable Logic Controll er (PLC)? http://www.amci.com/tutorials/tutorials-what-is-programmable-logic-co...
Structured Text (ST) – A high level te xt language that encourages structured programming. It has a language structure (syntax) that strongly resembles PASCAL and supports a wide range of standard functions and operators. For example; If Speed1 > 100.0 then Flow_Rate: = 50.0 + Offset_A1; Else Flow_Rate: = 100.0; Steam: = ON End_If;
Instruction List (IL): A low level “assembler like” language that is based on similar instructions list languages found in a wide range of today’s PLCs. LD MPC LD ST RESET: ST
R1 RESET PRESS_1 MAX_PRESS LD 0 A_X43
Sequential Function Chart (SFC) A method of programming complex control systems at a more highly structured level. A SFC program is an overview of the control system, in which the basic building blocks are entire program files. Each program file is created using one of the other types of programming languages. The SFC approach coordinates large, complicated programming tasks into smaller, more manageable tasks.
What Are Inp ut/Output Devices? INPUTS – Switches and Pushbuttons – Sensing Devices • Limit Switches • Photoelectric Sensors • Proximity Sensors
– Conditon Sensors – Encoders • Pressure Switches • Level Switches • Temperature Switches • Vacuum Switches • Float Switches
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OUTPUTS – Valves – Motor Starters – Solenoids – Acuators
– Horns and Alarms – Stack lights – Control Relays – Counter/Totalizer – Pumps – Printers – Fans
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AMCI : Tech Tutorials : What Is A Programmable Logic Controll er (PLC)? http://www.amci.com/tutorials/tutorials-what-is-programmable-logic-co...
What Do I Need To Consider When Choosing A PLC? There are many PLC systems on the market today. Other than cost, you must consider the following when deciding which one will best suit the needs of your application. Will the system be powered by AC or DC voltage? Does the PLC have enough memory to run my user program? Does the system run fast enough to meet my application’s requirements? What type of software is used to program the PLC? Will the PLC be able to manage the number of inputs and outputs that my application requires? If required by your application, can the PLC handle analog inputs and outputs, or maybe a combination of both analog and discrete inputs and outputs? How am I going to communicate with my PLC? Do I need network connectivity and can it be added to my PLC? Will the system be located in one place or spread out over a large area? PLC Acronyms The following table shows a list of commonly used Acronyms that you see when researching or using your PLC. ASCII BCD CSA DIO EIA EMI HMI IEC IEEE I/O ISO LL LSB MMI MODICON MSB PID RF RIO RTU SCADA TCP/IP
American Standard Code for Information Interchange Binary Coded Decimal Canadian Standards Association Distributed I/O Electronic Industries Association ElectroMagnetic Interference Human Machine Interface International Electrotechnical Commission Institute of Electrical and Electronic Engineers Input(s) and/or Output(s) International Standards Organization Ladder Logic Least Significant Bit Man Machine Interface MOdular DIgital CONtoller Most Significant Bit Proportional Integral Derivative (feedback control) Radio Frequency Remote I/O Remote Terminal Unit Supervisory Control And Data Acquisition Transmission Control Protocol / Internet Protocol
portions of this tutorial contributed by www.modicon.com and www.searcheng.co.uk
A small number of U.S. based tech companies design, manufacture and sell PLC modules. Advanced Micro Controls Inc (AMCI) is such a company, specializing in Position Sensing interfaces and Motion Control modules. The company's products are listed below for your reference: AMCI PLC Modules Index: Allen-Bradley | GE Fanuc | Schneider (please scroll to view)
Allen-Bradley: ControlLogix PLC
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CompactLogixPLC
MicroLogix 1500 PLC
POINT I/O
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AMCI : Tech Tutorials : What Is A Programmable Logic Controll er (PLC)? http://www.amci.com/tutorials/tutorials-what-is-programmable-logic-co...
Analog Inspection
Resolver Interface
Resolver Interface
Resolver Interface
PLS Control
PLS Control
SSI Interface
SSI Interface
SSI Interfac e
PLS Control
Stepper Control
Stepper Control
Stepper Control
Stepper Control
SLC500 PLC
PLC-5 PLC
Resolver Interface
Resolver Interface
LDT/SSI Interface
LDT/SSI Interface
PLS Control
PLS Control
EasyPack Series
EasyPack Series
PressPRO Series
PressPRO Series
GE Fanuc: GE Fanuc 90-30 Series PLC
GE Fanuc 90-70 Series PLC
Resolver Interface
Resolver Interface
SSI/LDT Interface
SSI/LDT Interface PLS C ontro llers
Schneider Automation: Modicon Quantum PLC
Square D SY/MAX PLC
Resolver Interface
Resolver Interface
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