1. PROGRAMMABLE
LOGIC CONTROLLER
SOFCON INDIA PVT. LTD.
MENTOR: SHEKHAR MAURYA
PROF. S.K.PAHUJA 09106068
INSTRUMENTATION &
CONTROL
2. PLC
The PLC is an assembly of solid state
digital logic elements design to make
logical decisions and provide outputs.
PLC is programmed interface between
input sensor &output device.
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3. Programmable Logic
Controllers
Advantages of PLC :
They are fast and designed for the rugged industrial
environment.
They are attractive on Cost-Per-Point Basis.
These Devices are less Proprietary ( E.g.. Using Open
Bus Interface.)
These Systems are upgraded more Capabilities with
dedicated PID and Ethernet Modules.
Disadvantages of PLC :
PLC one time cost is high
To maximize PLC performance a number of IO Modules
to be added.
PLC hold only one copy DEKprogram.
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4. P L C Components(Hardware)
CentralProcessing Unit (CPU)
Input Modules
Output Modules
Power Supply
Bus system
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5. Advantage of PLC Over Relay
RELAY PLC
1-More wiring 1-Less wiring
2-Changes difficult 2-Changes easy
3-More power 3-Low power
4-More maintenance 4-Solid state
reliability
5-Difficult to expand 3113 -Easy to expand
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6. PLC Cycle
Sense the Input
Process the Logic
Give Output
Inputs CPU Outputs
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7. Ladder Diagram
Ladder diagrams are specialized schematics commonly used to
document industrial control logic systems.
It is a language or a method to create a program. The first PLCs
were programmed with a technique that was based on relay
logic wiring schematics.
Basic concept of this diagram is similar to the electrical wiring.
However in ladder logic, the symbol has changed and been
standardized.
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8. Ladder Diagram cont..
Type of graphic language automatic control systems.
A drawing program of a switching circuit.
Called "ladder" diagrams because they resemble a
ladder, with two vertical lines representing the power
trails (supply power) and circuits are connected in
horizontal lines called rungs. Connection between the
element in the rung called link.
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9. Ladder Diagram Operational
Principle
Referring to figure below, between these two rails, a horizontal
straight line was drawn with two symbols. These two symbols refer to
the input and output devices, which are used in the actual
process/system.
On the left, we put all kinds of input. While on the right, we place all
types of the outputs.
Once we complete one line of the program it seems like a ladder. This
horizontal line which places the input and output make one rung.
+24V -0V
Input Interface Output
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10. Ladder Diagram Symbols
Ladder diagram uses standard symbols to represent the
circuit components and functions found in a control
system.
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19. Logic Function…cont
3. NOR logic
Since there has to
be an output when
neither A nor B
have an input, and
when there is an
input either A or B.
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26. Control Circuit
Start stop circuit
-PB is pressed, output IR is activated
-IR contact will closed
-When PB is depressed, the output IR is still
activated since current can go through contact IR
unless is disturbed by stop button.
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27. Vibrating/Jog circuit
-When, PB is pressed, output IR is activated.
-When, PB is pressed, output IR is activated.
-But after several microsecond, the normally closed IR is
-But after several microsecond, the normally closed IR is
open then will stop the output IR.
open then will stop the output IR.
-This applicable to move an object which need to locate
-This applicable to move an object which need to locate
at precise location.
at precise location.
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