Passive Buzzer

A Passive Buzzer requires an oscillating signal to produce sound, unlike an Active Buzzer which will produce sound with only DC power. A Passive Buzzer requires an AC current to run, and will produce a frequency range from 50 to 14,000 Hz.

How does a Passive Buzzer work?

The Buzzer consists of an outside case, with two pins to attach it to power and ground. Inside is a Piezo element, which consists of a central ceramic disk, surrounded by a metal, often Bronze, vibration disk. When current is applied to the buzzer it causes the ceramic disk to contract or expand. This then causes the surrounding disc to vibrate. That’s the sound that is heard. By changing the frequency of the buzzer, the speed of the vibrations changes, which changes the pitch of the resulting sound.

Using a Passive Buzzer in a Circuit

Unlike an active buzzer than will generate a tone using an internal oscillator, a passive buzzer requires an AC signal to make a sound. Therefore a changing input signal produces the sound, rather than producing the tone automatically.

A passive buzzer could therefore be used to indicate the push of a button with a short buzz, as the current through the component would change as the button is pressed.

In this example, the buzzer is used to play a simply melody, by varying the note played and the duration for which each note is played. The code used to do this is as follows.