₦airaland Forum

Nobody has responded to my question. Is the question tough? Even my number one student has not responded.
Do I need to explain the relay circuit all alone ? Nobody wants to stress his brain, why?

We are going to write an open test very soon. I will send an email address where you submit your answers to. Don't look down on what we are doing here. Many employers are following this thread.
You can't understand Automation and be poor for life. The employers look for you.
Please let's be serious in this class. Everybody should participate effectively

RELAY
You can't understand Automation without a good knowledge of relay logic.
Relay provides a good picture of ladder logic programming language. Relay consists of two things
a. Coil
b. Contacts
When coil is energized, the state of contacts changes. When de- energized, the state returns to original position.
I know by now everybody understands what coil is all about. Contact explanation will be made clearer as we progress.
Look at the picture of relay below and explain what you make out of it.

Class rep, am still expecting the list of inactive students

doghorp:
A contact has only two states: open or closed. An open contact breaks the current flow whereas a closed contact allows current to flow through it to the next element. The simplest contact is an On/OFF switch which requires external force (e.g. the human hand) to activate it. Limit switches are those small switches that are placed at certain location so that when a mechanical device moves towards it, the contact will be closed and when the device moves away from it, the contact will be open.
a contact is connected to a load and the contact is closed, the load will be turned ON

Thank you very much. Good explanation

What is Contact?
What does it mean?

Southboy:
Auxiliary contact(Normally open contact)

Good job

You should understand that your school work is just to assist you in knowing the real life engineering works.
Put your certificate aside and start learning a different thing that will change you for better.

The symbol above is very important and one of the most used in ladder logic programming.
It's not Capacitor.
Task your brain, research online and tell me what the symbol stands for

People should respond when I ask question. I don't like beating students but may start doing so if am forced to it.
Class rep, compile the list of class members that don't answer question.
I need the list tomorrow morning.
At long run, I shall present gifts to active students

Who can tell me what this symbol represent

I expected a lot of questions but none is coming. Does it means everything is well understood?
Please feel free to ask your question no matter how foolish it might sound

ClearDway4me:
Wow, just find this group when searching for something relating to automation.

God bless you op. I will fully once am done with exam but for now include my name in the class list

Our class rep @Southboy should note your name down and collect late registration fees

[quote author=Southboy post=125306008][/quote]Output

Now, everybody pay attention. This is a serious business.
What type of activities is represented in the bell circuit?
ON and Off bell
Is this activity digital or analog in nature?
Digital
What's the input signal for digital?
5vdc or 24vdc
What's the result of switch the circuit ON and OFF?
Inductor coil is Energized /De-Energized
What happens when the input is 1?
Coil is Energized
What happens when the input is 0?
Coil is de-energized
What's the output?
Coil
What action is triggered by the output?
Bell

Please study this over and over and ask your question

@Southboy got a and b.
From Automation point of view, he did not get c and d.
What's happening? Why afraid to make attempt?
More inputs please

[quote author=Southboy post=125299400][/quote]Thanks for your contributions. Very good input but you did not win the #500 recharge card.
Waiting for more inputs

Let get proper into the job. Class rep @Southboy, lock the class doors, make sure no student gets out.
Everybody must answer these questions:
From the bell diagram above, identify
a. The action control
b. The action itself
c. The input(Signal)
d. The output

Correct answer attracts #500 recharge card from me

Now, let me explain the circuit before we look into actions and control.
Looking at the diagram above,
a. There is no presence of magnetic field
b. Closing the switch cause current to flow in the coil introducing magnetic field
c. The two iron core containing the coil become magnetic (Electromagnet)
d. The long metal bar facing the magnet becomes attracted to the Electromagnet
e. This movement caused the bar to hit the bell
f. If the switch is opened, the magnetic property is lost, the spring push back the bar.

From the diagram above, two things are involved
a. Action
b. Control
First, you get to understand the action here and what controls the action.

I hope by now everybody has understood what Electromagnet is all about. This play very vital role in automaton and control industry. Let's consider the practical applications.
a. Bell application
When you understood this simple application, the same principle is applied in complex application.
The diagram below is open to the house for discussion.
Everybody get involved. What happen when current flows through the circuit?
That's when the switch is closed

Southboy:
Do you mean "note" or "not"?

Note

On the coil with soft iron core, the iron absorbs the magnetic field to become a temporal magnetic. The magnetic property is lost the moment the current is removed.
In summary,
The iron core becomes temporal magnet.
The iron core becomes normal iron, no more magnet, once the current is removed.

Here we get a situation where a material that's not originally a magnet, becomes one by simply applying a DC current to it.
This is what is called ELETRO - MAGNET.
We are gradually entering into CONTROL.

doghorp:
a. When DC Current is applied to a soft iron the magnetic flux is increased and the flux lines will be highly concentrated because soft iron have have high permeability it can strengthen the field and increase the working of a machine, it also have low reluctance which means it allows magnetic lines through them easily.

b. When the DC Current is removed it does not retain it magnetism in other word it does not permanently magnetized

Please note the following
a. There is no magnetic field of any kind on the coil until DC current is applied.
b. It's only applying DC current that brings in magnetic field.
c. The field builds up gradually before it gets saturated ( Full)
d. Removing the DC current, the field gradually fade off.

Summary, no DC current, no magnetic field

From @Southboy contribution, note the word TEMPORAL. This is very important.
Still need more inputs

doghorp:
a. When DC Current is applied to a soft iron the magnetic flux is increased and the flux lines will be highly concentrated because soft iron have have high permeability it can strengthen the field and increase the working of a machine, it also have low reluctance which means it allows magnetic lines through them easily.

b. When the DC Current is removed it does not retain it magnetism in other word it does not permanently magnetized

Very good answer. Keep it up.
I still want more inputs

I need respond to my questions above to move forward

Another question
a. How does the soft iron behave when DC current is applied?
b. When the DC current is remove?

Where are others outside Southboy, I want other people to make some input

The field produced on the hollow coil is weak and not concentrated. Some field is lost to the atmosphere.

The field produced on the coil with soft iron core is very strong, none is lost. The iron core capture all the fields and provided the right magnetic circuit for the fields to flow as can be seen in the picture above

Let's also consider the one produced on coil winded on soft iron core

Let's consider the nature and strength of the magnetic field produced in a hollow coil and compare it with that wound on soft iron core

Answering the question about the application of magnetic fields produced by both ac and DC current,
a. Ac magnetic field is used in Electromagnetic Induction
b. DC magnetic field used in Electromagnet
We shall channel our energy to
Electromagnet.

What is Electromagnet?

Southboy:
The rate at which the class is progressing is not encouraging oooooo. I keep refreshing this his page checking for update. Atleast let's put some structure in place e.g. Lecture time, so that everyone knows when to be in class and respond to any question asked.

I was too busy today. I can't fix time since I put up some write up when less busy.

Automation is built on Logic. You must be logical in your reasoning. Logic is equally built on knowledge, which means you must understand the system very well.
When a system stops working, it means that there is a missing signal. You must first determine the type and the source of the signal in the circuit. If you have a missing 5v or 24vdc signal, you must determine first where the voltage is coming from and the path of flow.

We are going to discuss or learn about CIRCUIT DIAGRAM. This is very important. When there is a fault or problem in a system, the first step you take is getting the circuit diagram. Without circuit diagram, you're not going anywhere. This diagram provides you the paths of signal flow, from there you can trace where the signal stopped.

Problems that has to do with current must be traced to current source, eg inductor. All these, we shall consider in details as we progress.
My motivation is active participation.
I wonder whether this class is meant only for southboy, others should get involved.