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Automation Lecture 4.
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transmitter
actuator
Structure of control system
Process
or plant
Material flow
sensorstransducer
actuating
unit
actuating
drive
controller
operator desk
Visualization software
SCADA (Supervisory control and data acquisition)
Simulation software
Control software
Standard signals
Variables
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Relay
When a current flows through the coil, the resulting magnetic
field attracts an armature that is mechanically linked to a moving
contact. The movement either makes or breaks a connection
with a fixed contact. When the current to the coil is switched off,
the armature is returned by a force approximately half as strong
as the magnetic force to its relaxed position. Usually this is aspring, but gravity is also used commonly in industrial motor
starters. Most relays are manufactured to operate quickly. In a
low voltage application, this is to reduce noise. In a high voltage
or high current application, this is to reduce arcing.
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PLC Programmable Logic
Controller
PLCs were invented as replacements for automated
systems that would use hundreds or thousands of relays,
cam timers, and drum sequencers. Often, a single PLC
can be programmed to replace thousands of relays.
Programmable controllers were initially adopted by the
automotive manufacturing industry, where software
revision replaced the re-wiring of hard-wired control panels
when production models changed.
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IEC 61131-3
Part 3 of IEC 61131 deals with programming languagesand defines two graphical and two textual PLCprogramming language standards:
Ladder logic (graphical) Function block diagram (graphical)
Structured text (textual)
Instruction list (textual)
The standard also defines both graphical and textualsequential function chart elements to organize programsfor sequential and parallel control processing.
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IEC 61131-3 Programming
languages /
Industrial Control Programming
Standardizing the way people work with controls
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IEC 61131-3 Programming
languages /
Industrial Control Programming...with support for people
with different background
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The IEC 61131-3 Programming
Languages
Instruction List Structured Text
Function Block Diagram Ladder Diagram
C:= A AND NOT
B
A BC
-| |--|/|----------------(
)
LD A
ANDN B
ST C
AND
A
C
B
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Sequential Function Chart, SFC
Powerful graphical
technique for
describing the
sequential behavior ofa control program
Used to partition a
control problem
Shows overview, also
suitable for rapid
diagnostics
Step 1 N FILL
Step 3
Step 2 S
Empty
Transition 1
Transition 2
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Program Organization
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PLC families example
Small compact PLC-s with low I/O capability
Small PLCs with extendable I/Os
Medium PLC-s
Large PLC-s
Process Stations
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Siemens LOGO
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Siemens Simatic S7-200
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Siemes Simatic S7-300
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Siemens Simatic S7-400
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Phoenix Products
RFC 400
IEC 350IEC 200
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