MakerSpace Buzzer music: Simple melodies with the Pi Pico Buzz It, Baby!

Use the buzzer to have your MCU play small wake-up melodies, signals, or music to accompany LED animations. The sound might not be a feast for the ears, but it does give your projects a great retro feel.

- By Bernhard Bablok

Every PC has at least a small beeper for signal tones. In the case of microcontrollers, you need to retrofit a buzzer to do this, but buzzers are too good for just outputting beeps. They are available for a small amount from the typical marketplaces, and you can choose between two basic types: active and passive. The active relies on a builtin oscillator to generate sound and only require two pins, while you need to feed a PWM signal to the passive. Besides voltage and earth, they require another pin for the signal.

The buzzers themselves look like small black pots with two pins (Figure 1, center and right). For active buzzers, you just need the component itself, but for passive buzzers, it makes sense to use a breakout with the required circuitry (Figure 1, left). There are also breakouts for active buzzers with three pins, but one of them is not assigned in this case. When purchasing, you can use the designation as a guide: Passive buzzers will be known as KY-006 or HW-508, while an active variant often has KY-012 in its name.

Because the parts are inexpensive, it’s a good idea to grab a handful of them. A single buzzer is fine for simple tone sequences, but it’s more fun if you have several of them so that you can create entire chords instead of just individual tones.

Pulse Width Modulation

PWM signals are levels that are switched on and off at fixed intervals, resulting in a typical square wave curve (Figure 2). The pitch of the buzzer output depends on the frequency. You could simply generate these PWM signals by switching a GPIO pin, but that would be painstaking and unnecessary. All microcontrollers have builtin hardware units for this; you just have to feed them the right parameters. In addition to the frequency, which is decisive for the pitch, this also includes the duty cycle, i.e., the proportion of active time that determines the volume.