Sound and Piezo Buzzers

Sound and Piezo Buzzers

Quick Review: Sound Frequencies

• Sound is created by vibrations in air pressure (sound waves)
• Commonly we measure the amplitude (volume) and the frequency (perceived pitch)

Piezo Buzzer

Piezo Buzzer

• Uses magnetic coil to vibrate a metal disc to produce sound
• Control the pitch by a form of pulse width modulation (PWM)

Uses of piezo buzzers

• Buzzer are small and cost-effective
• Can be used for alarms, games, toys
• Can produce tones and simulate single notes

Limitations of Buzzer

• Frequency
  • Human hearing is roughly 20 Hz to 20,000 KHz
  • Hertz (Hz) is cycles per second
  • Piezo buzzer operates up to 2.048 KHz
• Sound Quality
  • Only generate tones through square waves

Connecting Buzzers

Connecting Buzzers

• Buzzers are polarized so look for the +
• Negative pin to gnd and positive pin to Argon output

Producing Sound

Syntax

tone(<<PIN>>, <<FREQUENCY>>, <<DURATION>>);

• tone() generates a square wave using PWM (50% duty cycle)

• pin is connected the speaker

• frequency is sound frequency in Hz (20Hz to 20KHz)

• duration is the length of tone in milliseconds

Producing Sound

Example

tone(D6, 500, 1000);	// play 500Hz tone for 1000ms (1 sec)
tone(D2, 2000, 3000);	// play 2KHz tone for 3000 ms (3 sec)
tone(D2, 1000, 0);		// play 1KHz tone (don't stop)

A Note on Argon and tone()

• tone() requires a pin that supports PWM
• PWM pins are assigned to one of three groups
• Each group can have different PWM values (duty cycles), but must share the same frequency and resolution
  • Pins D4, D5, D6, D8
  • Pins A0, A1, A2, A3
  • Pins D2, D3, A4, A5

Stopping Sound

Syntax

noTone(<<PIN>>);

• To stop a continuous tone or stop tone before duration is over

Optional: Controlling Volume

Optional: Controlling Volume

• All tones will be at the same volume since Argon can change only frequency (not amplitude)
• To control volume, connect a potentiometer between negative and gnd
• Potentiometer acts a current limit resistor to control volume

Playing Melodies

• Musical notes can represented as constants
• Add this file (pitches.h) to your src folder and then add #include "pitches.h" to your sketch
• You can then refer to music notes in the following manner

tone(D2, NOTE_C4, 1000);  # play the note "middle C"	

Finding Notes of Popular Songs

• Notes for some popular songs (note that the format for playing notes is different in this code, but you can still extract the notes and duration from these examples)
• MIDI to C converter allows you convert a MIDI file directly into

References

• Images created with Fritzing
• Pixabay
• Sparkfun
• Neuton Foo