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2
I/O Module
The I/O interface section of a PLC connects it to external
fielddevices.
The main purpose of the I/O interface is to condition the
varioussignals received from or sent to the external input and
outputdevices.
Input modules converts signals from discrete or analog
inputdevices to logic levels acceptable to PLCs processor.
Output modules converts signal from the processor to
levelscapable of driving the connected discrete or analog output
devices.
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I/O Module
DC INPUT MODULE
OPTO-
ISOLATOR
IS NEEDED TO: Prevent voltagetransients fromdamaging
theprocessor.Helps reduce theeffects ofelectrical noise
CurrentLimiting
Resistor
FROM
INPUTDEVICE
USE TODROP THEVOLTAGETO LOGIC
LEVEL
Buffer,Filter,
hysteresisCircuits
TOPROCESSOR
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I/O Module
AC INPUT MODULE
OPTO-
ISOLATOR
IS NEEDED TO: Prevent voltagetransients fromdamaging
theprocessor.
Helps reduce theeffects ofelectrical noise
Rectifier,ResistorNetwork
FROMINPUTDEVICE
CONVERTS THE ACINPUT TO DC ANDDROPS THEVOLTAGE TO LOGIC
LEVEL
Buffer,Filter,
HysteresisCircuits
TOPROCESSOR
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5
I/O Module
DC / AC OUTPUT MODULE
OPTO-
ISOLATOR
IS NEEDED TO: Prevent voltagetransients fromdamaging
theprocessor.Helps reduce the
effects ofelectrical noise
FROMPROCESSOR
TTLCircuits
AmplifierRELAYTRIAC
XSISTOR
TO
OUTPUTDEVICE
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PLC
INPUTS
OUTPUTS
MOTOR
LAMP
CONTACTOR
PUSHBUTTONS
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OMRON PLC
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