Name: なぜコンピュータ全体をブレッドボードで作るのか？ (Why build an entire computer on breadboards?)
Uploaded: 2021-01-14T10:42:22.000Z
Duration: 28 min 43 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Is it a good idea to build an entire computer from scratch on bread boards like this?

様態の副詞

Well, might seem like a strange question for someone who's basically made an entire YouTube channel out of doing precisely that.

再帰代名詞

And I sell kits with all the parts so you can do it yourself.

So obviously, I'm a pretty big fan of building computers on bread boards, and the big reason I really like it is that it forces you to think through how everything works.

You know, they felt like something was missing with these projects, where you get a premade circuit board and you just saw her a bunch of components to it.

It's great if you want to learn how to Sauder, But once you know that, I just don't see how attaching a bunch of components to a circuit board teaches you much about electronics.

In fact, the typical experiences that you saw her, the whole thing together plug it in, and it it just works the first time.

There's no need to understand how it works, and so you don't this.

On the other hand, you know it really forces you to think about each individual connection to each pin.

And as you build each section testing, you know each as you go, there's a very good chance things aren't going to work perfectly the first time.

It forces you to think about why, and it helps you build a deeper intuition for how it all works.

And so that's what I really like about doing big projects like this on bread boards.

But aside from being a lot more work, which which I think is a good thing, there are definitely some caveats to be aware of when building complex projects like this on bread boards.

First, not all bread boards are the same.

There's a big difference in quality between the cheap $2 bread boards you can get and a higher quality, you know, eight or $9 bread board.

Each row on the bread board is connected with a metal strip that grabs the wires that are inserted, and if I dig under the backing here, um, I can remove that metal piece so we could take a closer look at it.

And here it is, what it looks like, have we take a closer look?

You can see the wires air inserted like this here and make contact with metal here and in a good quality bread board.

These this metal, it's nice and flexible, and you can see even if you, Anna, insert the wired kind of weird angle like this.

It it flexes like that, um, and then pops back nicely.

You can also see it's nicely shaped so that when you insert the wire from the top, which is which is what you'd be doing, Um, you know, it kind of finds its way in there nicely.

These make very good contact with wire spring back, So they last a long time on everything else.

Now let's take a look at the cheaper bread boards.

Construction on the cheaper bread board is pretty much the same, so it's actually pretty hard to tell the quality just by looking at a bread board.

Which is unfortunate because it means it's easy to pay for a high quality bread board and end up receiving one.

That's lower quality, and I may not even be the fault of the person selling it to you, since they may just not realise that there's such a big difference.

But anyway, here's the same piece from the cheap bread board.

So let's take a look at the difference, and you can see it's the same basic shape.

But right away you can see there's a huge difference here.

You know, the metal is just not, um, not a springy, and so it doesn't snap back together.

And so it may not make great contact with the wires you can see here, and it actually gets worse over time.

If you Ah, you insert something big, you can actually bend this out of shape.

And I mean, that's maybe a little bit extreme for what you might stick into a bread board.

But once that's bent out of shape, you know nothing.

You know you're not gonna make great contact there.

Um, and so the quality of this bread board in the quality of the connections you're going to get is much worse.

There's a big quality difference, and you can even see the, you know, just the shape of the of the top.

There where the wire goes in is very different, um, and much less consistent on the lower quality one.

So the quality the Bridgeport matters, you can run into a lot of problems building a more complex project like a computer on these cheaper bread boards, because you just can't be assured that all the wires are making good contact.

And you can check out my website for more information on what bread boards I recommend.

And, of course, if you get any of my kids, they're all gonna come with these high quality bread boards.

But okay, even with the best bread boards, there's still a lot of limitations to building a complex design, like a computer on bread boards, versus a custom printed circuit board.

Or even these, you know, Stoddard prototyping boards.

And that's because the physical properties of the conductors in a circuit, whether that's the traces on the printed circuit board or the wires and bread boards in something like this, you know, those conductors and everything have physical properties that affect the circuit.

For example, it's easy to look at two wires like this, you know, Let's say these two wires here and think well Okay.

You know, this wire connects this point here to this point here.

This wire connects this point here to this point up here, and maybe they don't really have anything to do with each other.

You know, anytime you have two pieces of metal close together like you have these two wires that are close together.

And that's why the schematic symbol for a capacitor is two plates next to each other, but not touching.

And the way a capacitor works is you have a difference in electrical potential on either side.

And a charge builds up between these two plates and another way of saying that you have a difference.

Electrical potential between two points is saying that you have a voltage across those points.

It's always, you know, sort of a voltage measured between two points.

And it's just the difference in electrical potential between those points.

If you try to change that voltage, um, the capacity rubble will actually try to prevent that.

Yes, if you try to increase the voltage Bye bye.

You know, adding more charge to one side, the capacitors actually gonna absorb that charge and charge up a bit before the voltage between these points actually changes.

And then if you try to decrease the voltage hereby, by pulling some of that charge away, the capacitor will discharge as much as it can to keep the voltage from dropping.

So, for example, in the power rails usually don't want the voltage to fluctuate, right?

And you know, we want five volts everywhere on our power rails to be actually five volts.

We don't want a dropping and things like that.

So if a if a chip is switching circuit on and off, and it has to draw more current to do that, we don't want the voltage on that power rail to drop.

And so it's actually a good practice to add some capacitors just across the power rail like this.

So actually, at a couple of 0.1 micro fared capacitors here across the power rails to help stabilize the five volts that are on this power rails and really the best practice here is to have one of these capacitors for every chip that's on in your circuit.

So, for example, we could have a capacitor here directly from five volts to ground across this power rail four for this chip here like this.

And that means that if this chip has has any change in the amount of current it needs to draw from the from its power rails, it's always going to see a consistent five volts or as close a cz close as we can get to that.

And the closer you can put the capacitor to the power inputs for any particular chip, the more the better stabilized the power's gonna be for for that ship.

And that's I guess one of the other maybe drawbacks of bread boards is that it's, you know, kind of hard or at least inconvenient.

To get these capacitors directly across the power rails of a chip like this, you've got to kind of put it across, and some of these chips, they're the powers were just kind of in an inconvenient place.

But I think you know, for what we're doing, it's probably good enough just to have a couple capacitors here these will still help stabilize the power rails without really getting in the way too much.

You know, we can add capacitors here if we want to stabilize the voltage and keep the voltage from changing like we do on our power rails.

But elsewhere, you know, we have signals that need to change voltage rapidly.

You know, any of these signals need needs to change full to drafted Lee because they're carrying signals on DDE that has to change.

And so the stray capacitance that inherently exists in the bread board we're even a printed circuit board can cause problems.

And, you know, since one factor that determines how much charge capacitor can hold is this is actually the physical area of the conductive plates.

In that capacitor, you're more likely to have a lot more capacitance in a bread board circuit just because you've got a lot more metal in here, you know, in the bread board and in all these wires, then you might have in other types of circuits.

Now, another related phenomenon is induct in CE, and if you've learned a little bit of physics, you might know that any time you have a current flowing through a wire like this.

There's a magnetic field that has generated around that wire.

Course, if you have a lot of wire, uh, especially wound up like this, you can use that magnetic field to do work.

And that actually works in reverse as well.

Right now, I'm using current to generate a magnetic field that's pushing against this fix magnet here.

But any motor is also a generator, and that's because a changing magnetic field around the wire will induce a voltage in the wire.

So when I spin this, the magnetic field from the permanent magnet changes relative to the wire and induces a voltage in the wire.

So what does this mean for a bread board computer?

Well, you know, if you've got a wire with the current going through it, you're gonna have a magnetic field around that wire.