PLC E-Learning Session 1 – Introduction to PLC & PLC Wiring


Ok. so Welcome to the Learn PLC in a Day Session
1, which is wiring the PLC. In this session we are going to learn about
– How to wire a PLC! Now when we are going to install a PLC, in
any panel or any machine, or in any process, first we have to wire up that. So we will understand that, how to wire a
PLC. Which wire is to be connected where? So very quickly, lets understand the basic
components of PLC. In front of the screen you can see ‘This is
a PLC’ by the company Delta Electronics. We have some Input terminals. Now these are the terminals onto which we
will connecting the Inputs. Now what are the inputs? Inputs can be switch,
it can be sensors, it can be limit switches, it can be any source of input signal (sensor) Then we have the output terminals. We can see here. These are the Output terminals..onto which
we will be connecting the outputs. Now what output or what input can be in any
machine depending on the various processes. For example: Suppose we are going in a lift. Now what you do – You push a button! The button is your Input. That buttons tells the machine, tells the
process or tells the lift, which floor you want to get into. So that movement of the lift is done with
the motor. And that is your output. So you understand that the button is the input
which will be connected to the input terminals and the motor will be connected to the output
terminals. But what happens inside that! That is the program. How the controller has been programmed? In a similar way we will program this PLC
using this ‘Programming Cable’ – That’s the programming cable! We have to make the program
in the computer, then we have to download that in to this PLC. Which will remain stored in that. So that’s what all about Programmable Logic
Controller. That’s what PLC stands for! Programmable Logic Controller. A Controller which can be programmed using
various Logics. Logics can be If-else, OR, NAND, NOT.. so
that’s the logic which we are using in our day to day life. The similar logic we can program in a PLC. OK let’s see further components! We have RS 485 terminal over here. Now this terminal is used to connect this
PLC to an HMI or any other communication source. So that we can communicate what’s happening
inside the PLC. Then we have D-A Card. This is Digital to Analog Card, which converts
digital data into Analog signals. In this case, digital data can be binary bits. These binary bits can be converted into analog
voltage which can be further used to drive different analogue outputs. Then we have A/D card which is Analog to digital
converter, which convert analogue to digital signals Now analogue signals can be given by analog
sensors. Now if you are from Instrumentation, electronics
or Electrical background! So you can understand, there are two basics
control signals – which is 0 – 10V and 4-20 mA. So there are sensors which gives these control
signals. So that signals needs to be processed. To process those signals we have to convert
that into Digital form, which makes the processing very easy. That’s why we convert analogue signal to digital
using this card. So these are the basic elements you will find
in many different companies of PLC. So i will show another PLC. That is of company Siemens- S7 200 CN. Similarly here we have.. This is the Power – 24 VDC which will be used
to RUN (power) a PLC. Then we have input terminals. As we have in Delta. These are the output terminals. Then we have this Programming cable, which
is used to program a PLC. That is the battery. Now this battery is used to store the information. To store the program, when there is.. in
case of Power failure. Now, another PLC of the company Allen Bradley-
Micrologix 1000. Similarly we have input terminals here, output
terminals here. And again Programming cable to program a PLC. Then power of 24 VDC which is used to RUN(Power)
the PLC. You can see some indications here, When PLC
is powered ON you can see this green light. When PLC is RUNNING, you can see green light
here again. When it is having some fault, there wil be
some orange light ON here, and where there is some forced Input, which we are running
the Input from Inside the software, instead of switches, then there will be FORCE light
here. So these are the basic components of What
PLC is all about! Ok, so this is the software in which we are
going to learn about – How to wire a PLC! This software is Automation Studio, by the
company Famic technologies, which is in Canada. And this software is being used in our academy
to teach the students – How to do the wiring! How to do the electrical wiring and how to
make the sophisticated circuit and how to test that.. how to simulate that. So that after making circuits in this Software,
we can implement that directly. So let’s take some PLC Cards. This is my PLC Input card. It is analogous to those Input terminals which
we have seen in that presentation. So.. Let’s take some power sources. Now this PLC, i assume is running on 24VDC. So i will take 24V and i will take 0V. So, as this is the software, this PLC is not
needed to connect to Power sources. This will be connected (powered) internally
by the software. But we have to provide the voltage to drive
the Inputs. So let’s understand how this input will be
RUN. How they will indicate that there is some
voltage or there is some physical activity outside this PLC. So you can see COMMON terminal here. Now i am going to connect this 0V to this
COMMON. Like this ! So my 0V has been connected to COMMON. Now we have to understand that – We need to
create a potential difference of 24V across these input terminals. Then only this PLC will recognize that there
is some input. For example, if i connect this 24V over here
(IN0). And then i am going to simulate that. You will see this is ON. This is ON because this 24V and 0V. 0V is
connected internally to this Input (IN0). So we have created a Potential difference
of 24V. To clear this understanding, lets take a relay. For example, i will take a coil. This one! Let’s name is r0. Alright! So let’s take another voltage source – 24V. And this one (0V). Now this is my relay, this is my electro-magnetic
relay. What happens, when i provide a signal of 24V
and 0V across it’s two terminals. You will see it is ON. The similar way, these are the internal relays
of the PLC. You need to provide 24V potential difference
across every element (terminal) to make it ON. So if i take another relay..like this! And let’s name it as r1. And i connect this with this.. and this..
ok let’s not connect it initially. Now you see, This relay is getting 24V potential
difference, this is ON. This is open from one end. Similar way, these all are open from one end. The are getting 0V from here, like this relay
is getting from here. but 24V is not provided. So when i provide this 24V this relay will
be ON. You can see here. Similar way, if i connect other terminals to 24V,
this will be ON. You can see here. So the concept is, we need to maintain the
potential difference of 24V across this input and the COMMON. Now in many PLC’s instead of 24V you may find
Line and Neutral, because that depends on the manufacturer, whether he is providing
24 VDC inputs or whether he is providing AC Inputs. In some PLC, you may find instead of 24V and
0V – it is written Live and Neutral. So in that case, you have to give LIVE over
here, L1 and instead of 0V, you have to give Neutral. So this can be in case of some different PLC. So we have to check it out on the PLC whether
it is DC Voltage driven or AC Voltage driven. So, let’s remove it out for a second. Now this was my input card. I am going to connect some input switches
here. Now this is my push button. Let’s take it x0. Now i have connected this to IN0. And again i need some power sources. Let’s take 24V. OK, so what happen if i don’t connect 0V over
here? Nothing gonna happen! It’s not going to get ON, because there is
no potential difference, there is nothing at the common end. So we have to connect 0V as well. Ok, so now i have connected a switch. What happen, this is a normally push button
which is spring loaded. When i press this switch, Input will be ON
and when i release it, Input will be OFF. So this is an Input switch. You may find such kind of switches in your
panel in some other machines. You may find some green button. So this button is connected in this way. This is connected to some input and COMMON
is connected to 0V. So similarly, let’s connect some other switches. This is my normally closed button (switch). As it’s symbol indicates, that it is passing
the signal in normal position. That is why it is called Normally closed. Because the switch is CLOSED normally. When i press this button it will be OPEN. And it is again spring loaded. When i release this button, it will be CLOSED
again. And this is Normally Open, Normally Open means
when i am not pressing this button, the circuit will be OPEN. When i press this button, it will be CLOSED. So these are the different types of switches,
which we can find in the inputs. Now let’s have a toggle switch. Let’s name it x2. It’s connected to IN2 and again this to here. Some more input buttons. These are again Normally Open Toggle switch. Now toggle means they are not spring loaded. They are retentive, they have retentive position. When it is OPEN it remains OPEN, when i CLOSE
it, it will remain CLOSED. So that’s the beauty of this switch. So i have connected 4 switches. So i hope you have understood that .. that
this is ON because we have 24V already across this terminal (IN1). This will be ON, when i press this button. And again similarly with these cases. So this in my input section. How we are getting the input from the outer
world and how PLC is judging the inputs just by this voltage! Again where we are going to have potential
difference, that input will be ON. So this was about the Input card of PLC or
we can say input terminals of the PLC. Now let’S see what happens at the Output terminals. For that i am going to have Output card from
here. You can see like this. So i am placing this output card little bit
away from input card to make the concept pretty easy. Similarly we have different outputs – OUT
0, 1,2, 3, 4..7 and then we have a COMMON. So similarly i am going to connect 0V, i can
take the wire from here to this COMMON terminal. Now here i will be connecting the output components. Not the switches,. but the output components. So let’s see what we have in output components. We have Coils, LED Display, Coil Unlatch,
Latch, Solenoid, Indicators.. so let’s take an indicator. Now this indicator is my light, so let’s name
it y0. This is an indicator light. I am going to connect the one end of this
indicator to this OUT 0. Now i have to give 24V to it’s other end. Again, to maintain the potential difference. Now what happen here is, Now when i simulate
that, This 24V is travelling to the one end and another end is not connected to the 0V. Why, because! in this case, it was already
connected here. But in this case, it is not connected! And this will be connected only after when
we will be do the programming. It won’t RUN when i press this button, or
when i press this button or this button. But how it will RUN that depends upon the
program. So this is my output not running right now. Let’s add some more outputs here. Let’s call it y1. So i have connected two outputs now and both
are not running, because i have not program the PLC. What does a program do? Program will link this Input section with
the output section. Suppose i want, by pressing this button this
first light should be ON, i have to make the program according to that. If i want, after pressing this one, i want
both outputs should be ON, again i have to change the program. I don’t have to change the wiring. I just have to change the program. Similarly if i want, by pressing this button,
both should be ON. I have to change the program only. Wiring is one time. Remember this! So this is all about the wiring! How we have to wire the input section, how
we have to wire the output section ? We can similarly connect some more inputs, we can
connect some more outputs. Like this.. So you can see here, now i have connected
6 outputs to the output section (terminals) and few inputs to the input section. Now in next session, we are going to see how
to make a program? How to make this outputs (indicator) glow
by using the programming? We are going to see how to do the programming,
that’s based on simple logics -OR, AND, NOT, IF, ELSE, TIMERS, COUNTERS. So that’s very interesting. Stay tuned, and if you have any doubts, kindly
post below this video .. if you have any doubts, i will clear it out. So this was all about the wiring.

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