Input/Output (I/O) Modules Video Lecture | Computer Architecture & Organisation (CAO) - Computer Science Engineering (CSE)

hello guys so we have been having a
lovely day in this video we will be
learning about the input and output
modules of a PLC system so for any
system which includes the blt system we
need an input and output at least one
input and an output so a normal data
processing computer a normal data
processing computer that V people use
say for example Excel PowerPoint and for
applications like that which which are
called data processing computers we need
inputs like keyboard inputs we need a
data input and we get the output on a
specific monitor or any output device
that is going to display the process
that has been completed
however PLC's which are essentially
process control computers the inputs are
usually input from various sensors like
heat sensor humidity sensor etc and the
output is usually a motor a solenoid etc
so a PLC which is a process control
computer has a different approach than a
data control computer or a data
processing computer which is our general
conventional computer so now let us look
at the input modules of a PLC so a PLC
essentially has four stages of input the
first stage is it it detects and input
the first stages it detects an input and
the second stage it determines what the
input is that is it processes the input
that is is the signal high or or is this
sensor low and things like that
now here the third and fourth stages are
conversion and isolation we will talk
about this in detail and the fourth
stage is the output block so to start
with the detection of an input you will
understand this better by this small
circuit diagram so this is the circuit
diagram of the input module of a PLC on
the extreme left
what you're seeing is is a switch when
the switch is turned on you get a supply
of 120 volts 60 Hertz or as in some
countries like us where you have 120 60
in India you have 2 40 50 Hertz and yeah
that depends on your supply so once a
supply comes from the input end what you
can see here is a converter this is your
converter block as we know a PLC can
work on voltages of plus or minus 5
volts DC supply so we definitely need a
step-down
voltage we definitely need a voltage
that has to be stepped down by by a lot
of amount we nee because at the output
at the CPU we need only plus or minus 5
volts now you have a converter here that
will convert the voltage into your
specific voltage and make the AC into a
pulsating DC and later the pulsating DC
is converted into a pure
continuous DC which is actually required
for your PLC program and what you are
seeing next here is an optical isolator
or an opto isolator what an opto
isolator does is it converts the
electrical signals it receives here it
converts the electrical signals received
here into light signals the major
advantage of this is that if your
electrical signals container directly go
into the CPU it might cause any damage
to avoid that what this optical isolator
or opto isolator does is it converts
these electrical signals into light
signals so these light signals there
these signals whether they are on or off
they are carried by using a light beam
so this light beam is produced by an LED
or a light emitting diode which I am
sure you guys know and now when one
after the conversion here this is gone
as DC voltage into the CPU so this the
output of the input module is to the CPU
right and the input for the output
module will be from the CPU right so the
input this is all about the input module
of a PLC system so this is very simple
it has a supply it has a converter which
converts the AC to DC into the required
DC and then the optical isolator or the
opto isolator which converts this into
light signals and then from here these
light signals into DC which finally go
into the CPU so now that we are done
with the input module let us have a look
at the output module so as you guys have
might have guessed by now the output
module works in the exact opposite way
of the input module so what did we have
in the end of the input module we had
the optical isolator right
we had the output logic and before that
we had the we had the CPUs input which
is your output loss so now here I get
input from the CPU input is from the CPU
and this is converted by using an
optical isolator into your DC so this is
my opto isolator
right and then as I have mentioned in
the beginning of the video what are the
output devices that are usually driven
by a PLC module we have talked about
motors we have talked about solenoids
and other things so to control these
motors we use some solid-state devices
so we use many other devices we use
mainly three kinds of devices I will
show you what the first one is a triac
the output of the triac is given to the
load so this is how and I am going to
give a trigger control to the triac from
a right and yeah that's very much it so
this is your converter this is your
trigger for the triac and the load is
connected there is connected after this
so the load can be a motor and this
output supply is 120 voltage AC which is
which is the usual if it is two-party
then it's two-party if it's 1 when it is
120 etcetera so instead of a triac you
could use a DC to DC converter or you
can use another converter that again
converts this output DC into the
required AC so you can use different
methods of control but the major point
to note here is the input is from the
CPU and after it comes from the CPU it
is again optically isolated and once
that is done the triggering is given
into a triac or any converter and that
converter controls your load which is
your motor whether it is turning on or
turning off that that is very much thing
now another point to note about this
input and output modules is we have
scene two circuit diagrams for input and
output logics for input logics it was
from the 120 voltage AC then optical
isolator here and then we had the output
there but and this was two CPU and for
the output module it was from CPU and to
the output device right now what I would
like to tell you is in any PLC system
not a single in never a single terminal
is used for example what the circuit
diagram we saw was just a single
terminal usually four input modules we
have four six eight twelve sixteen
thirty-two terminals which means in
addition to this we also have ground
terminals which means you can have eight
opto isolator x' like this eight
converters like this eight output logics
connected to the CPU like this so 4 6 8
12 16 and 32 those are the terminals
that are possible for the input modules
and for the output modules it is very
much the same so this is how the input
and output modules of a PLC system work
hope you have found this interesting
thank you for watching and have a lovely
day if you have an exam tomorrow all the
very very best