Component: Piezo Element

Objectives and Overview

This lesson introduces the piezo element component. In addition to all the other great things you’ve controlled so far with the Arduino, you’re also able to work with sound! Incorporating the piezo element will open up exciting new possibilities and enable you to create your own Arduino music instruments!

Lesson Objectives

• Become familiar with the piezo element component and explain how it’s used to create sound.

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Making Sound With Arduino

Up to this point you’ve manipulated light by programming LEDs and reading input from a photoresistor. You’ve worked with motion through reading the input of a potentiometer as well as programming the turns and steps of a servo motor. Now you’re going to enter into a world of experimentation that is totally new: sound and audio!

Introducing the Piezo Element

When working with sound, you’ll first need to attach some form of speaker component to the Arduino. One of the most commonly used is the piezo element. The piezo is attached to one of the Arduino’s digital pins, and it produces a beep when it receives a pulse of current. To generate different pitches, the pulse is sent at different _frequencies_. Once you start pulsing at these frequencies, the piezo’s beeps will blend together and generate tones.

The core component that you’ll use in this process is the piezo element. It’s a small black disc with two legs. Here’s a picture of one from Adafruit:

Connecting a piezo element is similar to how you connect an LED. One of the legs attaches to GND and the other to a digital pin.

Activity: Make Some Sound

For the introduction to the piezo, you’re going to be using an example sketch provided by Adafruit.

Supplies

• Uno board and breadboard
• Jumper wires
• Piezo element

Steps

The steps for this project are split between the circuit setup and the sketch itself. Since this sketch introduces new commands, there will also be a section explaining each new command.

Circuit

Refer to this fritzing diagram for the circuit setup:

1. Connect the Arduino 5V to the + rail on the breadboard.
2. Connect the Arduino GND to the – rail on the breadboard.
3. Connect one leg of the piezo to the – rail on the breadboard.
4. Connect one leg of the piezo to a digital pin on the Arduino. In this example, the connection is to digital pin 9.

Sketch

This sketch will cover how to output some basic sound from the piezo element. There are several possibilities that you’ll be able to experiment with after you understand the structure of the code. Let’s check it out!

/*
* Adafruit Arduino - Lesson 10. Simple Sounds
* Note (from Jonathan): This will continue to play the loop while
* the Arduino has power! The idea is to introduce the tone command.
* If you're tired of the sound and just want it to play ONE time,
* see if you can figure out what to uncomment.
*/
 
int speakerPin = 9;
int numTones = 10;
int tones[] = {261, 277, 294, 311, 330, 349, 370, 392, 415, 440};
//            mid C  C#   D    D#   E    F    F#   G    G#   A
 
void setup(){
 // no additional setup code
}
 
void loop(){
    for (int i = 0; i < numTones; i++){
      tone(speakerPin, tones[i]);
      delay(500);
      //noTone(speakerPin);
  }
}
Code language: JavaScript (javascript)

Let’s break the code down, and then look at some of the new commands that were introduced.

First, you’ll need to create some global variables. These are outside of void setup(). These need to be global so that you can able to access them inside void loop().

One of the variables is speakerPin which is set to the pin that the piezo element is connected to, in this case, it’s connected to pin 9. Remember, if you change the pin connection, you’ll also need to change it in the code.

Next, the numTones variable stores the total amount of tones that you’ll be playing. In this case, there are 10 tones, so this variable has a value of 10.

The last variable, tones[] is actually an array. Arrays are similar to variables but hold a list of values instead of a single value. In this case, the tones array contains all the tones that will be used in the sequence.

Now that all the variables and arrays are initialized, the Arduino is ready to output some sound! The actual pattern and sound happen in the void loop(), so let’s examine the code in that section.

The code is contained within a for loop() that iterates through the total number of tones and plays each tone in sequence.

The code within the for loop() will run for each item in the list until it hits the endpoint. In this case, the endpoint is when the total number of tones have been played.

The tone() command actually plays the sound. Let’s take a closer look since it’s a new command!

New Commands

tone(): This is the command for emitting sound from the piezo element, and it takes two arguments. The first is the pin that the sound should be emitted from, in this case, it’s the speakerPin variable that stores the pin number that the piezo is connected to.

The next parameter is the frequency of the tone to be played. In this example, tones[i] is used to play the tone for the associated step in the loop. Remember, i is the step in the for loop, and the loop is cycling through all of the notes in the original tones array.

Using tones[i] tells the Arduino that it should play the corresponding item in the array index that matches the step number.

You don’t need to play sounds this way. You also could use the following format (but it’s less efficient):

tone(speakerPin, 440) // this plays a middle A frequency

It’s good to know both methods of playing sound. Remember, as long as the second argument of tone() is a frequency, you can pass it in however you like.

noTone() is the other new command. It’s commented out in the code example, but this command terminates the sound being played from the pin that the speaker is connected to. It takes one argument: the speaker pin number. This is used to stop all sound generation.

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Going Further

Now that you know the basics of outputting sound from the Arduino, go ahead and explore some different sequences! Here are some helpful guides that include notes and their corresponding frequencies.

This link is to the official reference page from Arduino: Arduino Reference: tone()