Okay, we get a lot of questions about the basics of electrical control panels,
such as what devices and equipment we typically use,
how the devices are wired,
how to keep the control panel and the cabinet within a normal temperature range and so on.
A while back, we did a very detailed and easy-to-follow video on this topic,
and we received a lot of positive feedback.
If you have not already watched that video,
click on the link in the description
and that will take you to the RealPars blog
where you can watch the video and read the article as well.
But today, I am here at Pro-Control workshop in the North of Amsterdam,
They have some very cool industrial automation projects going on,
and we are going to shoot a multi-series video
reviewing an actual electrical control panel,
for you to see what the basic components of a control panel are,
how they are wired, the function of a thermostat and so on.
So in this video, we are going to review the basic of an actual control panel,
and I promise you this is not going to be just a normal review,
it’s going to be very in-depth, easy-to-follow and you are going to love it. I promise.
And in the next videos, we are going to learn about the other aspects of
this electrical control panel.
But before we get into the video,
don’t forget to like this video if you find it useful.
This keeps us motivated to create more valuable and easy to follow videos in the future.
And also as a heads up,
since we know many of you love Joshua’s professional voice,
he is going to take over the video from here
and explain everything and then I will be back again at the end of the video.
Stay tuned!
This is a control panel that is used for a system that turns wastewater into clean water.
An example of wastewater could be the water that comes out of the bathroom or the toilet.
This control panel controls the system that cleans this wastewater
and turns it into the drinking water. Pretty cool, huh?
This is a 2-door control panel.
As you may remember from the previous RealPars video about the basics of a control panel,
we mentioned that we name control panels
based on the numbers of doors that they have.
So you have one-door, two-door or three-door control panel enclosures
depending on how big of a panel you have.
The more equipment and devices you have,
the larger the control cabinet you will need.
This one that we have here is a two-door control panel.
Here on the front of the panel,
we have some switches that are connected to the PLC inputs and outputs.
The first one says ’Mute Buzzer’.
This is the button that you use and press when there is an active alarm on the system.
When there is an active alarm on the system,
the technician, engineer, or whoever is responsible on the factory floor,
presses this button to acknowledge the alarm and mute the buzzer.
That’s why we often call this the acknowledge button as well.
But you may ask, why do we need this?
Why should we press this button and mute the buzzer, acknowledging the alarm?
Well, first off, to state the obvious,
by pressing this button when there is an active alarm,
you only “mute” the buzzer.
Muting the buzzer means the alarm is still there
and still visible on the HMI,
but the buzzer has stopped sounding.
But why should we mute the buzzer and make it silent?
Well, the answer is simple,
because you don’t want that annoying, loud sound of the buzzer in your ears
while you are working to resolve the issue.
So when there is an active alarm on the system,
and it’s making that crazy loud noise,
the engineer or technician can press this button to mute the buzzer,
and in doing so, acknowledge that they are aware of the alarm as well.
Therefore, next time that you see an alarm on the HMI,
but there is no sound,
it probably means that somebody has already acknowledged the alarm.
Next, we have the ‘ESD Reset’ here
which I will get into shortly.
Below this switch,
we have the big red Emergency Shutdown push button
or the E-Stop as it’s often called.
As the name indicates,
you use this switch to shut down the whole system when there is an emergency,
and by doing this you can prevent damage being caused to the system,
or the people around it.
As you can see, it has some guarding around it, called a shroud.
This will prevent the button from being used unintentionally.
Emergency Stop devices are always close to where people work
in order to be useful,
but we have this shroud around it to prevent any unwanted use.
Why? Because if someone presses this button unintentionally
the whole system will be shut down completely.
Now, when you press the Emergency Stop switch,
a red alarm indicator appears on the HMI screen.
After the emergency is gone and you want to run the system again,
you can press the ‘ESD Reset’ button,
or Emergency Shut Down Reset, here,
to clear the alarm and the indicator on the HMI.
An Emergency Stop switch is designed to work as a normally closed switch.
That means this switch is closed in normal operation
and when it is pressed, the switch opens.
Now you may wonder why we have this Emergency Stop as a normally closed switch.
Well, let’s say that you have this as a normally open switch instead.
That means the switch is open in the normal state
and will be closed when it’s pressed, right?
Now, let’s say that unaware to you,
a wire that is connected to the lower part of the contact has been disconnected
and you are not aware of it.
Now, what happens when there is an emergency?
Well, when there is an emergency, you press this Emergency Stop switch,
BUT the switch will not work. WHY?
Because the wire has been disconnected and you are not aware of it.
You never want to put yourself in a situation like this.
Because this is too late and also too dangerous.
So what’s the solution here?
Well let’s repeat the same scenario
but this time replace this normally open Emergency Stop switch
with a normally closed switch.
With this normally closed switch in the normal state,
there is a 24-volt signal connected to the PLC input,
giving an Emergency Stop healthy signal to the PLC, or other safety systems.
When the switch is pressed, the healthy signal will be lost,
and that’s how the PLC, or safety system,
knows to shut down the whole system. Right?
Now imagine the switch is back to the normal mode,
but this wire gets disconnected for some reason.
What happens now?
In this situation, the healthy signal will be lost,
and the PLC sees that as someone pressing the switch, right?
So it shuts down the whole system.
So with this Emergency Stop switch,
if the wire connected to the switch breaks,
the PLC shuts down the whole system.
Yes, I know, an unwanted shut down is not what you want when a wire-break happens,
but this is much better than having an emergency
but not being able to shut down the system.
That’s why you always need to use a normally closed switch, for your Emergency Stop.
The Emergency Stop that I have here goes to the lock mode when it’s pressed.
So I press the switch, and as you can see,
the switch goes back to the lock mode.
Now to unlock the switch and turn it back to the normal mode again,
I can twist it like this,
and the switch will get back to the normal mode again.
On the back of the door, you see that the switch is wired all the way to the PLC input.
This is a BECKHOFF PLC.
The blue wires that you see here are digital input and output signals,
the white wires are analog inputs and outputs signals.
These wires come all the way from the sensors and actuators in the field
and get connected to the PLC.
Of course, we only have these switches on the panel door connected to the PLC
and the rest of the sensors and actuators
will be connected to the PLC once we install this control panel in the field.
The Emergency Stop that we have on the door
is connected to the PLC digital input card
as it only sends an on and off signal to the PLC input.
Now you maybe be curious how you should know which input on the PLC
you should connect the Emergency Stop to.
Well, this is simply done based on the wiring diagram that we have here.
In a later video, I will get into the details of the wiring diagram
and show you how simple it is to read and carry out the wiring on this panel.
Now let me give you an overview of all of the important components that we have for this panel
and also see how they are connected.
As I mentioned before, this is a BECKHOFF PLC.
The first module that we have for this PLC is a CPU.
The CPU works as the brain of the PLC.
As you can see, the CPU has a few LED indicators here,
a couple of Ethernet ports
and also a bunch of DIP switches right here.
Next, we have the input and output cards.
Of these cards, those with blue wires
are “digital” input, and output cards
and those with the white wires are “analog” input and output cards.
So you see that we use separate cards for digital and analog signals.
This PLC that we have here is a unit that includes a CPU
and a few input and output cards,
which together make up the PLC hardware.
Now let’s take a look at the wires that are connected to the PLC.
These wires come all the way through the trunking,
and then they are connected to these terminals here.
So one end of the wires are connected to the PLC cards,
and the other end is connected to these terminals.
Now later, when we install this control panel on the field or the factory,
the sensors will be connected to the other end of these terminals. How?
It’s very simple!
First, we make some holes on the bottom of this panel,
like the holes that we have here.
This is called a gland plate and allows the cables to come into the panel.
Then, we put them into the trunking
and connect them to the other end of these terminals.
Please note that I am using the term “cable” here instead of “wire”.
What's the difference?
“Wire” is a single conductor, like this,
but a “cable” is a group of wires, like this, that is covered in a jacket.
So wire and cable are different.
A wire is a single conductor
but a cable is a group of wire. Very simple!
Outside of the control panel, you use cables,
but inside the panel, you remove the jacket and use the wires.
Why? Because inside the panel,
you need to label every single wire.
Why labeling?
You need to label each wire to be able to make the uniquely identifiable,
which helps with troubleshooting if there is an issue.
The wire is labelled at both ends,
so you know exactly where each end terminates.
Moving on, as you can see,
the PLC is connected to an Ethernet switch via these cables.
From the other end, the Ethernet switch is connected to these devices
which we call Communication Interface Unit or CIU.
These interface units connect to the pumps that are installed in the field,
and that’s how the PLC can control the pumps.
So the PLC is connected to this Ethernet switch first,
then the switch is connected to these Interface Units,
and then the other end of the units are connected to the pumps.
Some field devices are connected to the PLC directly via wires,
and some others are connected via Ethernet cables.
All right, here we also have the power supplies.
The bigger one has 24-Volt DC output voltage
and 20 Ampere or sometimes shortened to Amp or Amps output current.
The small one has 12 Volt DC output voltage
and 10 Amp output current.
Both of these power supplies receive 220 Volt AC as input.
This bigger one gives you 24 Volt DC in the output here,
and the smaller one gives you 12 Volt DC on the output.
Now you may ask why we have two power supplies in this control panel
with different output voltage.
Well, that is simply because we have some devices in the control panel
that work with 24 volt DC and some other devices that work with 12 Volt DC.
We use this one to power the devices that work with 24 Volt DC
and this one for powering the devices that work with 12 Volt DC.
Wonder why the 24 Volt power supply has a greater output amperage
compared to the 12 Volt power supply?
This is because the number of devices,
or the devices themselves,
powered by the 24 Volt power supply
require more input current to operate
than those powered by the 12 Volt power supply.
We usually size the power supplies based on the amount of current output that we need.
For example, we have power supplies with 1 Amp,
3 Amp, 5 Amp, 10 Amp, and 20 Amp output current.
The more devices we have, the more current we need
and the bigger the power supply gets.
Easy, right?
So this was an in-depth overview of the essential components that you see
in an electrical control panel.
This video was brought to you by RealPars in partnership with
Pro-control here in the Netherlands.
They are experts at control system design and industrial automation.
They have a team of world-class automation engineers
and have been designing and implementing
industrial control systems in different industries for many years.
If you want to get in contact with them, you can check out their website at pro-control.nl.
That’s pro-control.nl.
We will put a link to their website in the description below the video as well.
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