and I like to make stuff.

Today we are here

to look at another project

from our Arduino Starter Kit.

Today

we are making this spaceship interface.

This is a simple project

designed to teach you about

simple inputs and outputs with Arduino.

This circuit is going to show you

how simple it is to connect

a small button

and a set of LEDs

to the Arduino board,

and how you can control

the LEDs through the button.

First I want to explain

a few concepts about Arduino.

First of all Arduino

is the size of a credit card

as you can see here.

We can program

using the Arduino development environment

that I am going to show you in a few minutes.

The idea is that we write instructions

in the development environment,

then we press the button

that turns the instructions into a program

and get downloaded into the Arduino.

Then the Arduino can interface

with the outside world

to implement any crazy

projects that you can come up with.

So this project is very simple.

We have a button connected to

pin number 2 on the Arduino,

and then we have three LEDs connected to

pin 5, 4 and 3

of the Arduino.

When I press the button,

these two LEDs that are now

blinking will stop blinking,

and the yellow LED will turn on.

If I release the button

the two LEDs will keep blinking.

So,

this is a very simple

circuit that allows us to

control the behavior of these 3 LEDs

from this button.

Let's have a look to the code

that we need

to implement this behavior.

At the beginning of the code we have

this line that says

const int redLed1 = 5,

so this creates a constant

called redLed1 that contains the value 5.

This is actually a very clever technique

that allows us to give a meaningful name

to pin numbers.

So, throughout the code

I don't have to use the numbers

but I can use redLed1

to remember that particular pin

is associated with the first red LED.

And if you look, there are another

couple of lines

where you defined constant

for redLed2 and greenLed.

Then, later on we have another

constant called switchPin = 2.

This specifies that a switch

or a button that we are using

is connected to pin number 2.

Then let's look at the setup.

The setup() is that part in your

Arduino code that gets executed once

when the board is powered on or reset,

This means also right after

you upload some code into the Arduino.

So, as I said, this gets executed only once.

We see the instruction pinMode().

pinMode() basically tells Arduino

that we want to make sure that

pins, redLed1, redLed2 and greenLed

are all configured as outputs,

because the input and the output pins

of the Arduino can be configured

to assume both configuration.

Then we have an instruction called

pinMode(switchPin, INPUT),

which is used to specify that

the pin number 2 is connected to a switch.

And then we want to make sure

that is an input so we can read from it.

Now let's have a look of the loop section.

The loop section in your code

gets executed over and over

as long as the board is powered on.

We created a variable

called switchState and then we say

switchState = digitalRead(switchPin)

Basically what this does

is to read the state of the pin

connected to the pushButton

and it returns a value HIGH or LOW

depending on the fact that the button

is pressed - HIGH - or released - LOW

Then we are going to use

a clever statement called if,

which is very important

whenever you write some code

because this "if" statement allows us

to take decisions.

In this particular case

we basically ask Arduino

if (the switchState == LOW)

do something.

So in this case, we used

curly brackets to group

lines of code together.

You can see that

this

"if" statement

is followed by a question,

a condition that needs to be verified.

and then the curly brackets

specify which lines of code

need to be executed

when the condition is true.

In this case, switchState == LOW;

basically says if the button

is not pressed,

and then we follow that

with a series of digitalWrite()

statements that are used to

turn on and off the LEDs

and to implement this particular

blinking behavior.

After that we have a

delay of 250 milliseconds

followed by a short blink cycle

that happens on the other red LEDs.

The instructions that you see

in this section

of the "if" statement

are used to implement this

blinking behavior that you see here.

Afterwards,

there is a statement called "else".

Else is a statement that allows

you to basically create a fork

in the road in your Arduino code.

With "if" you can say

if something is true, execute this

piece of code. And else says

if that condition is

not true, then execute

this other piece of code.

So you can have two different

paths of your code that get executed

depending on the condition,

if that condition is true or false.

In this case, when the button is pressed

then we use two digitalWrite()

to turn off the red LEDs.

And we use one

digitalWrite(greenLed, HIGH)

to turn on the green or yellow LED

like we have here.

So if I press the button, the LED

turns on. If I release the button,

the LEDs are blinking.

So this is all the code

that we need in order to

implement this behavior.

I want to remind you that the code

that's inside the loop

statement will be executed over and over.

so as you can see

the blinking pattern is executed.

Then

Arduino reads the input,

checks if it's true or false.

So depending on that it decides which

behavior to implement

and then loops back

from the beginning.

That's all for today.

I hope you enjoyed the tutorial.

And remember: build it,

hack it, share it,

because Arduino is you!