SparkFun Inventor's Kit Experiment Guide - v4.0

Contributors: Joel_E_B

Circuit 2A: Buzzer

In this circuit, you'll use the RedBoard and a small buzzer to make music, and you'll learn how to program your own songs using arrays.

Parts Needed

Grab the following quantities of each part listed to build this circuit:

New Components

Buzzer

The buzzer uses a small magnetic coil to vibrate a metal disc inside a plastic housing. By pulsing electricity through the coil at different rates, different frequencies (pitches) of sound can be produced. Attaching a potentiometer to the output allows you to limit the amount of current moving through the buzzer and lower its volume.

New Concepts

Reset Button

The RedBoard has a built-in reset button. This button will reset the board and start the code over from the beginning, running what is in setup() and then loop().

Tone Function

To control the buzzer, you will use the tone function. This function is similar to PWM in that it generates a wave that is of a certain frequency on the specified pin. The frequency and duration can both be passed to the tone() function when calling it. To turn the tone off, you need to call noTone() or pass a duration of time for it to play and then stop. Unlike PWM, tone() can be used on any digital pin.

Arrays

Arrays are used like variables, but they can store multiple values. The simplest array is just a list. Imagine that you want to store the frequency for each note of the C major scale. We could make seven variables and assign a frequency to each one, or we could use an array and store all seven in the same array, as shown below. To refer to a specific value in the array, an index number is used. Arrays are indexed from 0. For example, to call the first element in the array, use array_name[0];; to call the second element, use array_name[1]; and so on.

Hardware Hookup

The buzzer is polarized. To see which leg is positive and which is negative, flip the buzzer over and look at the markings underneath. Keep track of which pin is where, as they will be hard to see once inserted into the breadboard. There is also text on the positive side of the buzzer, along with a tiny (+) symbol.

Volume Knob

All of the circuits in Project 2 make use of a potentiometer as a rudimentary volume knob. Notice that only two of the potentiometer's legs are used in these circuits. In these instances, the potentiometer is acting as a variable resistor, limiting the amount of current flowing to the speaker and thus affecting the volume as you turn the knob. This is similar to the current-limiting resistor used to limit current to the LED in circuit 1A --- only this time the resistance is variable.

Ready to start hooking everything up? Check out the circuit diagram and hookup table below to see how everything is connected.

Circuit Diagram

Note for Advanced Users: If you know how to read datasheets and schematics, you can also refer to the schematic below as an alternative.

Having a hard time seeing the circuit? Click on the image for a closer look.

Hookup Table

Open the Sketch

To open the code, go to: File > Examples > SIK_Guide_Code-V_4 > SIK_Circuit_2A-Buzzer

You can also copy and paste the following code into the Arduino IDE. Hit upload, and see what happens!

language:cpp
/*
  SparkFun Inventor’s Kit
  Circuit 2A - Buzzer

  Play notes using a buzzer connected to pin 10

  This sketch was written by SparkFun Electronics, with lots of help from the Arduino community.
  This code is completely free for any use.

  View circuit diagram and instructions at: https://learn.sparkfun.com/tutorials/sparkfun-inventors-kit-experiment-guide---v40
  Download drawings and code at: https://github.com/sparkfun/SIK-Guide-Code
*/

int speakerPin = 10;               //the pin that buzzer is connected to

void setup()
{
  pinMode(speakerPin, OUTPUT);    //set the output pin for the speaker
}

void loop()
{

  play('g', 2);       //ha
  play('g', 1);       //ppy
  play('a', 4);       //birth
  play('g', 4);       //day
  play('C', 4);       //to
  play('b', 4);       //you

  play(' ', 2);       //pause for 2 beats

  play('g', 2);       //ha
  play('g', 1);       //ppy
  play('a', 4);       //birth
  play('g', 4);       //day
  play('D', 4);       //to
  play('C', 4);       //you

  play(' ', 2);       //pause for 2 beats

  play('g', 2);       //ha
  play('g', 1);       //ppy
  play('G', 4);       //birth
  play('E', 4);       //day
  play('C', 4);       //dear
  play('b', 4);       //your
  play('a', 6);       //name

  play(' ', 2);       //pause for 2 beats

  play('F', 2);       //ha
  play('F', 1);       //ppy
  play('E', 4);       //birth
  play('C', 4);       //day
  play('D', 4);       //to
  play('C', 6);       //you

  while (true) {}     //get stuck in this loop forever so that the song only plays once
}


void play( char note, int beats)
{
  int numNotes = 14;  // number of notes in our note and frequency array (there are 15 values, but arrays start at 0)

  //Note: these notes are C major (there are no sharps or flats)

  //this array is used to look up the notes
  char notes[] = { 'c', 'd', 'e', 'f', 'g', 'a', 'b', 'C', 'D', 'E', 'F', 'G', 'A', 'B', ' '};
  //this array matches frequencies with each letter (e.g. the 4th note is 'f', the 4th frequency is 175)
  int frequencies[] = {131, 147, 165, 175, 196, 220, 247, 262, 294, 330, 349, 392, 440, 494, 0};

  int currentFrequency = 0;    //the frequency that we find when we look up a frequency in the arrays
  int beatLength = 150;   //the length of one beat (changing this will speed up or slow down the tempo of the song)

  //look up the frequency that corresponds to the note
  for (int i = 0; i < numNotes; i++)  // check each value in notes from 0 to 14
  {
    if (notes[i] == note)             // does the letter passed to the play function match the letter in the array?
    {
      currentFrequency = frequencies[i];   // Yes! Set the current frequency to match that note
    }
  }

  //play the frequency that matched our letter for the number of beats passed to the play function
  tone(speakerPin, currentFrequency, beats * beatLength);
  delay(beats * beatLength);  //wait for the length of the tone so that it has time to play
  delay(50);                  //a little delay between the notes makes the song sound more natural

}

/* CHART OF FREQUENCIES FOR NOTES IN C MAJOR
  Note      Frequency (Hz)
  c        131
  d        147
  e        165
  f        175
  g        196
  a        220
  b        247
  C        262
  D        294
  E        330
  F        349
  G        392
  A        440
  B        494
*/

What You Should See

When the program begins, a song will play from the buzzer once. To replay the song, press the reset button on the RedBoard. Use the potentiometer to adjust the volume.

Program Overview

Inside the main loop:

1. Play the first note for x number of beats using the play function. a. (Inside the play function:) Take the note passed to the play function and compare it to each letter in the notes array. When you find a note that matches, remember the index position of that note (e.g., 6th entry in the notes array). b. Get a frequency from the frequency array that has the same index as the note that matched (e.g., the 6th frequency). c. Play that frequency for the number of beats passed to the play function.
2. Play the second note using the play function
   ...and so on.

Code to Note

Coding Challenges

Troubleshooting