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  • Hi I am Massimo Banzi

  • and I like to make stuff.

  • Welcome to another tutorial

  • taken from our Arduino StarterKit.

  • Today we are going to build

  • a small musical instrument.

  • You can see, it’s again

  • a simple circuit.

  • We have four buttons

  • connected to the Arduino

  • and a small piezo speaker

  • orpaizospeaker

  • depending on where you come from.

  • So let’s press the buttons

  • and see what happens.

  • Each button

  • is associated with a note.

  • Every time I press a button,

  • Arduino produces a sound

  • through the piezo speaker.

  • So, how does this work?

  • Let’s start from the circuit.

  • You can see here there are four buttons.

  • But the four buttons are connected to the

  • Arduino board with just one wire.

  • In the previous examples,

  • weve seen that

  • for every button we had a wire

  • going to the Arduino board

  • We were using one digital pin

  • to read each individual button

  • and here we have four buttons

  • connected to just one wire,

  • because we have built

  • what is calledresistor ladder

  • That's a combination

  • of resistors and buttons.

  • When I press one of the buttons,

  • I create a combination

  • of resistors

  • that let current flow through them.

  • But then the voltage

  • that the Arduino board measures

  • out of this resistor ladder

  • changes depending on which

  • button I press.

  • So, each combination of buttons

  • produces a different voltage.

  • You know that

  • voltages applied to an analog input

  • can be read from the Arduino

  • using analogRead().

  • Then using a

  • series ofifstatements,

  • we can actually say

  • ok, if the value is

  • between this number and this number,

  • it's because I pressed the first button.

  • If it’s between

  • another set of numbers,

  • I pressed the second button.

  • And I could experimentally figure out

  • which one of the buttons

  • I pressed

  • by looking at

  • all the numbers that come out

  • when I press different buttons

  • that correspond to the combinations

  • of resistors.

  • Now

  • the output of this circuit,

  • the actuator, is this piezo speaker.

  • The piezo speaker

  • is a very simple device made of

  • piezo electric material

  • that has this feature

  • that whenever you power it

  • with electricity, it will make

  • a small click.

  • If you turn on and off

  • the power to the piezo speaker

  • at a certain speed,

  • these sequences of clicks

  • make a sound.

  • So, for example,

  • if I turn on and off

  • the power 440 times per second,

  • I produce a sound, which is a very

  • well defined note.

  • In our code,

  • as we will see in a few minutes,

  • we have defined all the different

  • frequencies of each note.

  • And when you press the button,

  • the Arduino detects

  • which button has been pressed,

  • and then plays that particular note

  • on the speaker.

  • Now let’s have a look at the code

  • and let’s read it line by line

  • to understand exactly

  • how to implement this behavior.

  • Let’s start from the beginning.

  • You can see on this line

  • that we are defining

  • a new type of variable,

  • called an array.

  • This is a variable

  • called "notes"

  • that contains four

  • different integer values.

  • Each one of these

  • integer values represents

  • the frequency associated

  • to a certain note.

  • In particular

  • these are the middle C, D, E,

  • and F notes.

  • This will be useful later

  • when we detect which

  • button has been pressed,

  • we can then

  • choose the right frequency

  • to play on the speaker.

  • Then we have the usual setup()

  • where we have a Serial.begin()

  • to begin a communication

  • with the computer.

  • Let’s look at the loop now.

  • The first thing we do,

  • we create a variable called "sounder"

  • that contains the value read

  • from the analogPin(0)

  • that represents the combination of

  • keys that have been pressed

  • on the keyboard.

  • Then we print that

  • value on the serial monitor,

  • so we can

  • look at it on the computer

  • and then we start to understand

  • which button

  • has been pressed.

  • So we do this by looking at

  • the "sounder" variable

  • using a set ofif

  • andelse ifstatements to

  • segment values in different bands,

  • and figure out in which band

  • the value falls.

  • Each one of them corresponds

  • to a sound.

  • So, at the beginning,

  • when the value is 1023,

  • then we know

  • that we have to play the middle C.

  • We are using a new function

  • called tone()

  • Tone() is able to produce a sound

  • on a small speaker or a piezo speaker

  • connected to a certain

  • pin on the Arduino.

  • The only thing we need to do is,

  • we need to say

  • this is the pin where

  • the speaker is connected to,

  • in our case, 8.

  • And then we have to

  • specify the note

  • and that note will be played

  • on that pin.

  • Then

  • if we continue down

  • the source code, you can see

  • there’s a number ofelse if

  • statements that divide

  • the value of "sounder" in

  • different bands.

  • So

  • we have a band that goes

  • between 920 and 1010

  • that corresponds to the middle D,

  • a band that goes between 505 and 515

  • that corresponds to the middle E,

  • and finally

  • a band that goes between

  • 5 and 10 that represents

  • the middle F.

  • If none of these combinations

  • is actually detected,

  • then there’s a finalelse

  • statement that you can see here.

  • Thiselsestatement calls this

  • function called nonetone() that

  • stops any sound being

  • produced on the specific pin.

  • So we say notone(8)

  • and this stops

  • the sound.

  • Let’s try

  • again the instrument and see

  • how our software is actually

  • working here.

  • At the same time, I will open

  • my serial monitor so that

  • we can see the numbers

  • while I press the button.

  • At the moment we see a value,

  • which is very

  • close to 0,

  • which represents the fact

  • that no button has been pressed.

  • So, we press the button

  • and we got 1023.

  • The second button is 1002.

  • The third button is

  • about 512

  • or something.

  • And the last one is

  • sort of between 15 and 20.

  • This

  • is in a very simple

  • way, a small

  • music instrument that you can build

  • very quickly with your Arduino,

  • a piezo speaker,

  • a few resistors and a few buttons.

  • This is all for now

  • but remember: Build it,

  • hack it, share it,

  • because Arduino is you.

Hi I am Massimo Banzi

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A2 初級

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    Chuan Zhe Lin に公開 2021 年 01 月 14 日
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