ChrisPLC.ppt

7/28/2019 ChrisPLC.ppt

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Current State

A PLC is a small, self-contained digital computer

Real time (output of the PLC is produced withina specific time bound relative to input data)

Encased in protective housing to allay extremeenvironmental conditions

Have multiple ports for inputs and outputs (more

ports = greater cost)Connect to sensors, actuators, and other outputdevices



Current State (continued)

May come in a modular form, such that additional I/Omodules may be attached

Programmed directly through the PLC via buttons andlights, text displays, GUIs, or through a connected PC

with appropriate softwareUtilize networks for communication





Uses

Who: Automated factories

Amusement parks

Any type of control system (could be used for a smalldevice that responds to inputs)

What for: Factory control (machines, conveyors, storage

retrieval, etc)

Device response control

Force regulation on park rides

Many more



Uses (continued)

When:

Whenever automation is required or humanskill is not great enough to operate a machine

Whenever great precision is required

Under difficult environmental circumstances



Costs

~ $50 to $5,000

Cost depends on the number and type of inputs andoutputs, PLC processor speed, modularity of the PLC

Additional costs for additional I/O modules

Economic for situations in which production quantitiesare not very large as to allow a custom-designed control



Supporting Technology

Communications RS-232, RS-485, Ethernet, coaxial

Personal Computer for software editingProgramming Languages: FBD (Function block diagram) LD (Ladder diagram) ST (Structured text, similar to the Pascal

programming language)

IL (Instruction list, similar to assembly language) SFC (Sequential function chart)

Adequate Sensors



References

http://www.allaboutcircuits.com/vol_4/chpt _6/6.html

http://www.omron.com/products/indu.html

http://www.eod.gvsu.edu/~jackh/books/plcs/chapters/plc_intro.pdf

http://www.jlab.org/accel/ssg/Pss/plc.pdf http://www.eod.gvsu.edu/~jackh/books/plcs/html/plcs.html#pgfId-864358



Application Rules and Limitations

Useful in situations that require outputresponses to given inputs

Can only respond as fast as input andoutput devices can send and receive data

Though rugged, still limited by operatingenvironment (i.e. 0 to 50 deg C, 10-90%humidity, 2000m or less altitude, etc)



Vendors



Standards

IEC 61131-3

Defines 5 standards-based programminglanguages (listed earlier)



Technical Paper

Title: Multi-axes sun-tracking system with PLC control for

photovoltaic panels in Turkey.

Authors: Sungur, Cemil1

Source: Renewable Energy: An International Journal;

Apr2009, Vol. 34 Issue 4, p1119-1125, 7p

A solar panel, attached to an electromechanicalsystem and controlled by a PLC, is oriented tofollow the sun’s position over a year so as toattain greatest solar energy input



Integration

Principles of automation are based upon controlsystems

Automation breaks down if it cannot respond tovariation, which is unavoidable

PLC’s act as the brains of the control system,interpreting real time data to alter the way thesystem operates



Video

http://video.google.com/videosearch?q=PLC&emb=0&aq=f#q=christmas%20light%20music&emb=0

http://video.google.com/videosearch?q=PLC&emb=0&aq=f








Class Application

A device must determine temperature,speed, acceleration, and pressure. Thedevice must then take this data and adjust

to follow a user defined speed andacceleration (through the use of 2 stepper motors). If a PLC were used to control this

system, how many inputs and outputswould it need?



Summary

Modern automation is built upon the backs of PLC’s PLC’s are highly customizable and may be altered toachieve a variety of tasks

PLC’s are an inexpensive alternative to highlyspecialized control systemsPLC’s require user defined programming in order toproperly adjust for given inputs

As processing capability has increased with time, so toohas the ability of PLC’s to perform an even wider rangeof tasks

A PLC may only be as fast and accurate as the sensor inputs

Documents

ChrisPLC.ppt