I have already assembled a model of a traffic light.
It is small and it doesn’t have a body frame, but it can work like a real traffic light.
The only difference is that ours is controlled manually.
Like this.
[NOISE]
Please, note that my traffic light is functioning correctly
and it has all the phases, including the red and the yellow lights which are on simultaneously.
Now let’s have a look at the details which I used for creating this model.
Indicators are LEDs which are connected via resistors.
I control each colour with the help of a tact switch. The power supply is connected to the board
via a technical block and is supplied by 4 AA batteries.
To be honest, the most interesting thing for us here is this rectangle
with holes, the so-called solderless breadboard circuit.
It is needed to connect all these components without the need to solder them.
You can assemble, dismount
and rebuild the circuit, it’s totally easy.
There are different types of solderless breadboard circuits: small ones,
bigger ones, even bigger ones and finally large ones.
But their mechanisms are always the same.
These holes hide metallic conductors which clamp your details.
Each of these rows of 5 holes is connected inside.
I am going to demonstrate it by opening one of these breadboard circuits.
[NOISE]
As you can see, there are metallic clamps here.
I have removed one conduct rail out of the breadboard circuit so that you could see these clamps
which are holding your details.
In the bigger breadboard circuit they are all the same, and the only difference is that
along its sides there are long rails through which power is usually conducted.
This is why they are marked with symbols of “+” and “-“.
One shouldn’t think that there is a battery inside the breadboard circuit
It’s just that the power unit has wires connected to these rows, and the rails are quite long here.
Look how all the details that we are going to insert into the breadboard circuit in one row
are all going to be connected with each other.
The rows and the vertical bars are numerated with letters and numbers.
Don’t pay attention to it, as it might only be useful for you if you want to
let somebody know where exactly you would like to insert the LED header, for instance.
So these rows are all absolutely identical, and their host of functions is the same.
One more thing to point out is the fact that
all these wires that connect details with each other,
are actually identical, although they are of different colours. .
You must be wondering
why on earth you have assembled a manually controlled model.
For starters, we just need to remember some facts about
how electric circuits are organized.
We won’t get too deep into electrical physics, because you can
read many outstanding books on this subject and even watch some online courses.
We need to remember that our circuit contains a power unit.
Its poles hold the difference of the electric potential.
And if you close them together, an electric circuit will appear.
As we remember, electric circuit is the ordered motion of electric charges.
Running through conductors, charged particles can perform some work,
for example, heat them up or create a magnetic field.
In our case, we are interested in LEDs, which begin to emit light
when the electric current runs through them.
Let’s remove one LED from the board to have a closer look at it.
Firstly, we can see that its headers or leads are all of different length.
One of them should be connected to the positive pole of the power unit,
which is called anode, and the other one to the negative pole, known as cathode.
The electric current can run through the LED only in one direction.
While the current runs through it, it emits light.
Let’s put it back now and have a look at the resistor.
In this case, we need the resistor,
so that the electric current which runs through the LED would not be too strong.
Every element has its own performance limits,
and these LEDs allow only 20 mA to run through them.
If you want to conduct the same experiment, take the 200 ohm resistors.
You can tell them apart by their coloured marking.
Let's see what happens if we connect the LED without the resistor,
and when the electric current is too powerful.
I am removing the resistor and spreading the LED headers wider.
Spread them wider, and here they are.
Now let’s turn it on.
[NOISE] This LED will never start again.
In this case, to switch on the LED, we are using the tact switch.
Unless it is on, the circuit is not closed, and there is no electric current
running through this section, therefore, the LED cannot be turned on.
Let’s sum up our understanding of how this model works.
The power unit creates power in our electric circuit.
Its positive pole is connected to the terminal block and then, with the help of the red wire,
it gets to the positive long rail.
The same happens with the negative pole, but through the black wire,
and from the other side of the breadboard circuit.
Then, 3 wires connect the positive pole with 3 switches.
By pressing each of them, you open up the further way for the electric current.
And it runs through resistors which, as we already know,
are an absolute necessity for LEDs, finally running to LEDs which emit light.
Each section closes in the minus rail.
I would also like to pay your attention to the fact that
the electric current can heat up the conductor.
Beware of short circuits, when the poles of the power units are closed directly,
without any payload between them.
And now we are going to sacrifice one of the components so that you could see
what this might lead to.
You already know that the rows in the breadboard circuit come in a series connection.
Now without any payload I am going to insert
the power unit in the same row.
Make sure you never do this.
Oh, look, something is emitting smoke here.
This must be the breadboard circuit.
It’s on the point of catching fire, so I might as well turn this whole thing off.