Lecture 2.1 - Electrical Components

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En provenance du cours de University of California, Irvine

Interfacing with the Arduino

1432 notes

University of California, Irvine

Interfacing with the Arduino

1432 notes

Cours 3 sur 6 dans Specialization An Introduction to Programming the Internet of Things (IOT)

Arduino senses the environment by receiving inputs from add-on devices such as sensors, and can control the world around it by adjusting lights, motors, and other actuators. In this class you will learn how and when to use the different types of sensors and how to connect them to the Arduino. Since the external world uses continuous or analog signals and the hardware is digital you will learn how these signals are converted back-and-forth and how this must be considered as you program your device. You'll also learn about the use of Arduino-specific shields and the shields software libraries to interface with the real world. Please note that this course does not include discussion forums.

À partir de la leçon

Module 1

IoT devices involve a combination of software and hardware. This module provides background on the basics of hardware design and wiring needed to build useful circuits. This module describes the functions of basic passive components and describes how to use them in simple circuits. This module also describes how to wire circuits together using a breadboard. The goal of this module is to enable students to design and implement the circuits they need to interact with basic sensors and actuators.

Lecture 2.1 - Electrical Components8:34

Lecture 2.2 - Diodes5:26

Lecture 2.3 - Switches, Potentiometers7:04

Rencontrer les enseignants

Ian Harris
Professor
Department of Computer Science

[MUSIC]

[SOUND] So we're still talking about electrical circuits,

about the hardware side of these IOT devices.

Now, you know, we understand V equals IR, Ohm's law and so forth, that relationship.

But you're eventually gonna have to actually build these things physically.

You're gonna have to take these components.

And we saw a battery, some kind of power source, wires, resistor.

There are lots of different components.

Eventually you're gonna have to take these and actually plug them together and

make a circuit out of them.

Okay?

Now, typically, when you do that, you also have what's called a schematic diagram.

And we're gonna show some of these.

But, so you start off.

Usually when, say you're thinking of a new design.

What you do is you write, you draw out a schematic.

A drawing of what should be connected to what.

Now this schematic drawing, typically, it shows what components connected to what,

what terminals connect to what.

But it doesn't show exact placement.

It doesn't show how it will physically look in the real world.

It shows, though, how you would expect it to be connected electrically.

So these schematics, we're going to have to get used to reading these schematics.

And given a schematic,

you're going to have to get used to taking that schematic and implementing it.

Meaning wiring some components together according to the schematic, okay.

So that's the type of stuff we're gonna cover right now.

And so we're gonna go through some of these electrical components

that you commonly see, just so you know what they look like and

what their schematic symbols look like.

So that you can understand what a schematic diagram looks like, and

then you can understand how that matches the actual physical implementation that

you're gonna work on.

So up here we have resistors.

So on the left you see a batch of resistors so those

are your standard resistors and they can look different but that is a common look.

So if you look at those resistors and

you can see next to it there's a schematic symbol that little

saw tooth type of diagram saw tooth thing that's a resistors schematic symbol.

Now a resistor, it provides resistance to the current flow.

So we already talked about what a resistor's supposed to do.

A resistor has two terminals, two leads, right, two wires coming out of it.

If you look at any one of those resistors there's two wires, one on each side.

And it doesn't matter which one, they're equivalent, so current could flow either

direction through there, it doesn't matter which one is which, which side is which.

Now, each resistor has a certain resistance value associated with it.

Maybe this resistor is 10 ohms, maybe this is 10 k ohms,

meaning ten kilohms, maybe this is 100 ohms, and so on.

So every resistor has a resistance, and

that resistance is encoded in the bands on the resistor.

Now I'm not actually gonna go through the band coloring but

let me tell you how it basically works.

These resisters generally have either four bands or five bands of different colors.

I think the ones on the screen, hard for me to see at this distance, but

they have four, maybe it's four, four or five.

So one of the bands, at one end is always

the accuracy of the resistor value.

So say I got a resistor and I say, oh it's 100 ohm resistor.

It might not actually be exactly 100 ohms, that's plus or minus 5%, or plus or

minus 10%, or something like that.

So that plus or minus percent, that's represented in the last band.

So typically resistors we have,

they have a gold band as the last band, which means pretty good.

I forget what that means.

I think it's 5%, plus or minus.

And then silver I think is 10%, something like that.

So there's one band at one end that is how accurate the value is on the resistor.

The other bands, each band represents a digit.

So if you were to Google resistor color codes.

You'd see these tables where they'd show black, I believe black is like a zero or

something and brown is a one.

Every color is a digit, and these bands.

So say you got a four band resistor.

One band is the accuracy, but the other three bands they represent three digits.

It's basically scientific notation.

So the first two digits are just two digits of a number.

So let's say it's a two and a two.

So two two.

And the last digit is the exponent of ten.

So let's say I had two two three.

That would mean 22 times ten to the third.

That's how many ohms resistance the resistor is.

So that's how you read them, so you need to have the color code sheet in front you,

it's sort of a tedious thing.

You can read the colors off of the band and figure out the size of your resistor.

It's tedious also because the coloring.

How good is your estimation of color?

Meaning they all have, there are kind of shades of colors that look kinda similar.

Like the orange sometimes looks like the red, things like this.

It is awkward to read these bands.

But that's what you have to do.

So now, what I actually do.

Tell you the truth, I have tons of resistors.

I basically, when I get them, they come in a bag that says what resistance they are.

I just keep them in that bag.

So I never have to read the bands again.

But you can always resort to reading the bands if you have to.

So just Google it and you can find the color codes and that's that.

So those are resistors and that's their schematic symbol.

Okay, here are some more schematic symbols for some common components that you get.

First, we got the battery.

Now, notice the battery has, basically, it's a long bar and a short bar.

The long bar is the positive terminal.

The short bar is the negative terminal.

Now, sometimes, you're driving something with a battery,

but sometimes you're driving it without a battery.

You just have a power source, maybe from the wall, or some arbitrary power source.

So, for instance, actually, in our examples,

all of our examples, we're not using a battery.

We're using the Arduino itself, right.

The Arduino, we're gonna pull five volts and ground from the Arduino itself.

So we won't use a battery.

Instead we'll just have a power symbol and a ground symbol on our diagram.

Power is actually drawn several different ways but

we're gonna use a little triangle that points up like that.

That's usually power.

And next to it you'd have the power of the voltage value.

So for instance, if it was a five volt source, you'd take power,

you'd have the little triangle.

And next to it you write five V.

Plus five V.

Something like that.

Now ground is actually always drawn, almost always drawn exactly like that.

Ground is just, it goes down and it says three bars, smaller one after the other.

So those are some common symbols, you see those in schematics all the time.

DC power.

So, this is all direct current, DC.

Just to note this, we're dealing only with direct current.

So, to tell you what direct current is,

there's direct current versus alternating current.

Alternating current is when current goes back and forth.

The electrons move back and forth.

Like coming out of the wall I believe we got 60 hertz.

Yeah, I think its 60 hertz coming out of the wall.

Which means 60 cycles a second, so the current goes back and

forth 60 times every second.

That's alternating current, alternating current is good for transmission.

Meaning it loses less power in long distance transmission.

Okay? That's why we have alternating current

in our houses and things like that because you gotta transmit

it from wherever the power station is, and it transmits there.

But direct current is what we use in our devices in our houses.

So there's always this conversion from AC to DC, to DC,

direct current, into our devices.

Like a TV or something like that, that runs off a DC.

All of our circuit boards, Arduinos, all that junk, that runs off of DC.

One other note, never create a short circuit.

So short circuit, actually specifically a short circuit between power and

ground, short circuit is when you accidentally connect two wires together.

If you were to short power to ground, so if you took power and

ground and wired them together by accident then power,

what happens is between those two points, you got, let's say power is five volts.

So you've got a five volt difference between ground and

power, but their resistance is zero.

If you have a conductor, if you've run a wire,

you've got effectively no resistance.

Now if we were to go back to Ohm's law V equals IR, right so

I the current equals V over R.

V divided by R.

If R is close to zero then I is infinite or approaching infinity right.

So what that means is if you short power and ground you get a rush of current and

something smokes.

Literally smokes, I mean you'll see something on your boards.

Smoke coming at you, you'll smell it, it'll be extremely hot.

It's not overly dangerous because we're dealing with low current levels, right?

But you don't wanna do that.

And you can mess up your bread board too, it'll brown out a hole and

it might hurt in the future.

So you don't wanna do that.

So never put a short between power and ground.

Thank you.

[MUSIC]

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