Peter Wheeler: Hello again.
Today, I'd like to talk to you about a product or a tool let's say that you're going to use
in your laboratory for your experiments in electric circuits.
This tool is known as a solderless breadboard, more commonly just known as a breadboard.
What we do with this tool is we end up connecting components into this breadboard in such a
manner that they're electrically connected.
As a result, you can then start to do your lab experiments.
This, for example, is a breadboard that you will find in your toolkit.
One of the things that some students don't realize is that these holes that you see are
actually connected.
The gauge of wire, and let me just write that.
The gauge of wire is on the order of 22 or 24 gauge wire.
As far as wire gauge goes, what does that mean?
Basically, if you think of a pipe and how many of these wires you can put in, versus
say this pipe, the more wires you can put in, the higher the gauge.
The fewer wires, the lower the gauge.
This breadboard manages, in the early days we can manage 24 gauge wire.
As the springs that hold the wire in these holes loosens, then you tend to use a little
larger wire.
These wires are jumper wires that you will use to interconnect your circuit.
Jumper wires.
All right.
If we look at this breadboard, a couple of things you should notice.
You notice that it's labeled.
There is a plus and a minus which is the same as in a battery for example.
We have a plus terminal and we have a minus terminal.
They're trying to show the polarity of the bus.
The electrons don't really care what is printed on the board.
However, it's up to you to keep certain, let's say, orientations of the schematic and the
components in an order that allows you at least to troubleshoot, if not to at least
put this thing together quickly and accurately.
One thing that we have here is if you notice these holes here, actually they're all tied
together.
That's as if there is a wire, a solid wire underneath tying all those holes.
The same thing with this one.
Even though this is labeled plus and this one is labeled minus, it is also all tied
together.
This again is also tied together as is the one beside it.
Yeah, I think it's like that.
This is known as a bus.
This will be our power bus or power rail.
That is fine there.
We also have some other connections as you'll see with these dots.
Here for example, these are tied together.
These are tied together.
Notice the gap in between.
There's a physical cut in the board.
There's a detent in the board here in the center that separates those smaller buses.
Again, these are tied together in this manner.
We go down through the whole board till you get down to the bottom here.
Why do this?
Well, it's for the ease connecting parts together.
For example, I'm going to put a circuit together.
Let's say this circuit here.
This is a schematic.
This is a battery and it has some voltage.
We show like that.
This is resistor, R1 of some value, let's say 1000 ohms and this is another resistor,
R2 of some value, let's say 2200 ohms.
I ask you to put the circuit together and what we're going to do in this lab for example,
a simple lab is we're going to measure, let's say the voltage across R2, VR2.
You could twist wires together.
You could find a soldering iron or clips, leads with clips on them.
You can go through a lot of, let's say, variations on the theme, but the easiest thing to do
is just take this circuit and implement it as a prototype on a breadboard.
I'm going to use this one over here.
What we'll do is I'm going to put a battery.
I'm going to use a battery.
Let me just use a small battery here.
If you've noticed the nine volt battery, they tend to look like this and something like
that.
This is the plus side to the nine volt battery.
This is the minus of course.
What I'm going to do is I'm going to take one of my jumpers and I'm going to, in this
case here, I'm going to do this.
I'm going to tie it to the negative rail and I'm going to insert my wire into my negative
rail.
I'm going to take my plus lead from my battery and I'm going to insert it in my positive
rail.
I'm also going to do something else.
I'm going to make this a black wire, a black jumper and I'm going to make this a red jumper.
Why?
Because it helps you keep track of polarities.
What's going to happen here in this circuit is that current will flow and it will flow
in this manner.
It goes from, in this case here, from the plus of the battery to the negative return
on the battery.
Everything comes out of here will have to be returned back there.
In doing so, it will go through R1, it will go through R2 and we're going to measure this
pressure.
This pressure here, let's say this is a nine volt battery, that is the pressure pushing
the current through these two resistors, but what's actually happening here through R1,
you're going to take some of the pressure off and you're going to take the rest of the
pressure off with R2.
The exercise of the lab will be to measure the voltage across R2.
There are laws out there that have been developed by scientists who've done a lot of work on
this basically by doing experiments like you're doing and there's one called Ohm's Law.
That says the pressure is equal to the flow times the resistance.
The pressure in volts is equal to the flow in current times the resistance in ohms.
What's the lab going to ask you to do?
The lab is going to say, "Please put this circuit together and take these measurements."
Instead of doing the calculations which you could do, which you will do, you want to see
how the lab results measure up to what it is the theory telling you.
Let's put this circuit together.
Now, we need R1.
I'm in the bus here from R1.
I know this is all positive coming down here.
What I'm going to do is I'm going to take a jumper and I'm going to put it in the hole
over beside it.
I know these are all connected together, so not a problem.
I'm going to put a jumper in let's say to here.
I know these are all joined together.
I'm going to put in here my resistor.
I'm going to put the lead in right beside there.
It's going to have a physical body that's going to look something like that.
I'm going to bring the other lead down to here.
Again, there's a space there, so I don't worry.
This line here is joined together.
This is joined together here.
We're taking the plus from here into this connection over here which is isolated.
As you'll see, electrons don't like to jump across gaps.
Then we're going to take it through the body of this resistor into this point.
This is going to be our R1.
We need another resistor, we need R2.
I'm going to take R2 here, as you can see I'm right beside it and I'm going to put it
in right to here.
Did I miss the dot?
That's good.
Then beside here, I will take another jumper into that bus.
Now, I've completed my circuit.
All I need to do is take my volt meter and simply place it across R2 and take a reading
in volts.
One of the problems students have when their circuit is not working, they need to troubleshoot.
One of the issues that we've seen is there are times when you will put, not intentionally,
but you'll put a resistor like this.
Basically, you have taken this resistor here and effectively connected a wire underneath
it.
In other words, the current, when it sees the resistance says, "I don't need to go this
way.
I can go a shorter path.
I can go a less resistant path.
I can take a short circuit."
When students put the resistor across that connected bus, that shorts a bus there, points
there.
They end up shorting that resistor out and there's no value there, so they don't understand
why the measurement is off.
The truth is, is they simply didn't pay attention to keeping ...
You could do it this way.
You could do it this way for example.
As long as you don't do it this way, you'll be fine.
The resistor will be isolated.
The second thing is when some students need to join to this point here.
Let's just call this node A for now.
When you need to create the so called node A here, what this sometimes do is they miss
and as a result, these two points are separated and you've got a gap again.
We've got a gap again and the electrons don't jump across the gap.
From a troubleshooting perspective, you got what is known as an open circuit.
You got one resistor here and then you got a space and then you got the other resistor
here.
You need to understand that you have to make an electrical connection which means that
the wires have to be touching and that you have to avoid problems like this as short
circuits so that you're not actually taking a part out of the circuit.
Those are the two, basically the two main problems that people are being introduced
to electronics usually see.
Let's just take this one step further.
The breadboard is not just used for passive components like resistors or capacitors or
inductors.
It's also used for integrated circuits which you'll get to soon enough.
One of the things about an integrated circuit is, it looks like this.
I'm just going to draw over here an integrated circuit.
It's essentially a plastic case.
It will have a dimple on one end to indicate a direction.
What's happening here is that coming off there will be a lead and a lead and a lead and a
lead.
Some of these have many leads.
This one, let's say there's four on this side and four on the other side.
This dimple indicates that this is number pin one.
This is number pin four.
We count this way.
This will be five and we'd get over to eight over on that side.
Again, in a similar fashion, we need the pins separated on this IC.
We cannot short them out.
What we tend to do is we'll tend to use this open part of the breadboard.
If this is our dimple here, this will be pin one will be in there, two, three, four, five,
six, seven, eight.
You use the gap to isolate the integrated circuit pins.
Again, remembering not to put the chip this way.
You don't want to do this, because your pins would short.
They'd be shorted.
You don't want to do that.
This is wrong, this is right.
Again, this is a problem.
Again, if you put them across and you violate ... Here, you got a piece of wire underneath,
not that.
Also, this is a problem here because you got an open circuit and the electrons won't jump
it.
Keeping those types of things in mind.
You should be able to go from a schematic, a diagram showing the circuit which this is
here to your breadboard with no issues.
One final word.
If you have the opportunity to actually lay your board out in the same manner of the schematic
is, it will give you another visual clue as to how to put this together.
This is our two buses for example here and you may have preferred then to have laid this
circuit out this way.
This would have been the plus.
This would have been the minus and you would come in and then you would go to ... Again,
remember, you have to go across.
The resistor is like that and then from here, you may just want to do ...
If you have the center gap, you could ... I'm getting a little bit carried away here.
You could do it this way.
In fact, you could do it all the way down to here.
Don't forget, these are tied together.
I've created that point.
This will go off to my battery.
This will come from my battery.
You can lay your breadboard out this way.
It doesn't have to be in this manner.
In fact, if you lay it out to what you see the circuit to be, it will probably go a lot
quicker in your layout, your selection of jumpers and obviously minimizing your troubleshooting
issues.
Thank you.