So I don't have any data to back this up,
But I feel pretty confident in saying that
The resistor is the most common electronics component in the world.
It is used in practically everything.
It's used in setting operational amplifiers, getting that feedback loop setup,
voltage dividers, current limiters for LEDs and so many other things.
They're just everywhere.
So we're gonna go over that really quick and we're going to learn more about resistors
and what we should pay attention to with them.
So the resistor symbol is actually very straightforward.
There's the European resistor symbol,
and then there's the American or the most
Well, for Americans, more standard resistor symbol.
And as you see, they are actually quite similar.
So that's pretty nice.
However, the challenge comes when you're looking at the actual physical resistor itself.
Even though on your schematic they look the same,
in reality, resistors look wildly different.
So I have here what one would consider the most stereotypical resistor.
And this is an axial lead quarter watt through-hole resistor
and this is when people think of resistors, basically, what you think of.
It's got the color bands to show you exactly what the resistance is
As well as a band showing the tolerance of this.
And so this is the stereotypical resistor.
However, resistors come in all shapes and sizes.
So I also have here with me a small bag of resistors.
Now. These are 0603 resistors.
And they are absolutely tiny and they're not even close to the smallest they have out there.
The smallest one that I am able to actually solder is an 0402.
Which is quite a bit smaller than this
and the smallest ones are so small
I wouldn't even try, even using my microscope, to solder.
They're so small.
And resistors also come in the other size.
They get huge.
My father-in-law makes elevators and he designs control boards
and he uses these massive brown o'my resistors
to control the flow of electricity when necessary.
And when I first saw that, I was still in school
and I did not believe that they were resistors.
I thought my wife was just messing with me.
But no. You can see resistors in all shapes and sizes.
So if you see something and somebody says it's a resistor,
They're probably not lying too
Even if you've never seen it in that package before.
So don't be surprised if you have some that are through-hole, that are surface mount.
As you saw here, they're chassis mount, panel mount, any variety.
Again, since the resistors are so ubiquitous
They are in every package style, every mounting style that you can imagine.
So now the good news is that resistors are very easy to use.
They're highly linear.
As the voltage changes, the current through them changes linearly.
There's not much that you have to worry about in terms of parasitics.
There is a little bit of inductance and a little bit of capacitance.
But it's so tiny that most the time you just completely ignore it unless you're doing RF circuits.
And frankly, they're just very straightforward.
So the basis of a resistor is that, as the resistors put into the circuit,
The electrons go to it and it slows that flow of the electrons.
It resists the flow of electrons so that you won't have nearly as much going through it.
So very frequently, when people use water as an analogy
A resistor is like basically a point
where the pipe gets smaller
so the water struggles to get through it.
So, a bigger pipe means lower resistance.
Smaller pipe means higher resistance.
Less current or less water flow, using that analogy.
Now the behavior of electricity through resistor
is very easily described using Ohm's law.
V equals IR or voltage equals current times resistance.
Now I'd like to emphasize this law because it's so important
To get a fundamental understanding of how electricity works.
Now going back to that analogy,
You can see that voltage, which is the pressure
Pushing the water versus the current which is the actual flow of the water
Would be related to the size of the pipe.
So Ohm's law shows that linear relationship
And is really helpful to get an intuitive understanding of what to do when you're trying to set the current
or control the current in a circuit.
So when you're choosing a resistor
Some of the most important things to figure out is obviously the resistance.
That's the biggest one.
But you also need to know what the power reading is.
How much current and at what voltage is going to be through and across this resistor
Because too much power and too small of a resistance.
Again, this is a quarter watt resistor.
You try and put too much power through this thing,
And you are going to have some serious issues.
That large resistor in the picture from the elevator controller
That obviously is more in the tens to hundreds of watts.
Where these are more in the quarter two tenths of watts.
So again, figure out the resistance,
the power and dissipation capabilities.
You also want to know the tolerance.
Most resistors like this, the tolerance is 5%.
You want to pay more to get more like 1%
You can even get down, I think, to .01, .001%
Of course, the price just keeps on ramping up
And if you don't need that sort of precision,
You usually want to design around it and you don't want to pay for it.
And then finally, the thermal coefficient.
You want to make sure that as you're in a hot place or cold place,
It's not going to throw off the resistance of your resistor.
Because you could have your circuit in the Antarctic
and it acts one way or the Sahara and it acts another way.
You want to make sure that you either have a resistor
that doesn't have an issue with that temperature coefficient or you're gonna design your circuit
so that any sort of deviation from that ideal resistance is not a big deal.
Finally, as I mentioned earlier, resistors are great
In that they're very linear and they don't get affected by frequency.
However, again in reality, all of them have a little bit of inductance and a little bit of capacitance.
So if you're gonna be doing a high frequency circuit
You want to be making sure that your resistor has minimal capacitance or minimal inductance
or at least that you know what it is so that you can take that into account
When you're designing your circuit.
And that's really it.
Resistors are very straightforward but incredibly powerful.
And for the most part you can just drop them in and it's not until you start doing More production level designs
that you need to worry about.
Exactly all of those tiny little details, but for most just prototyping hobbyists work.
You can just buy a package of these things and use them in almost every single project you have.
And then from there, change what you need and if you're going to start doing your PCBs
You can start buying these tiny ones so that you can make your circuits even smaller.
Alright, that's it for now.
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