What Is a Buzzer?
A buzzer is a small audio component that converts the electrical signal given to it into sound (a beep, an alarm tone). It's used in devices for warnings and feedback.
Active and Passive
There are two basic types. An active buzzer contains an oscillator; it produces a fixed tone with just a DC voltage. A passive buzzer has no oscillator inside; an external frequency (square wave) signal must be applied for it to make sound.
| Type | Drive | Tone |
|---|---|---|
| Active | DC only | Fixed (single tone) |
| Passive | Square wave (PWM) | Varies with frequency |
Which Should You Choose?
If a single "beep" is enough, an active buzzer is the easiest. If you need different tones, a melody or to change the frequency, a passive buzzer and a PWM signal are needed.
Driving
Most buzzers draw little current but can still be near an MCU pin's limit; a transistor is placed in between for louder sound. Magnetic buzzers contain a coil, so a flyback diode may be needed.
Where Is It Used?
Home appliances, alarms, meters, toys, medical-device warnings and key-press sound/feedback.
Magnetic and Piezo
Buzzers are also split by sound-production method: a magnetic buzzer uses a coil-diaphragm, while a piezo buzzer vibrates a piezo element. The piezo type is more efficient and thinner at high frequency.
Common Mistakes
- Mixing types: giving only DC to a passive buzzer makes no sound.
- PWM to an active buzzer: trying to change its frequency doesn't work.
- Direct drive: a loud buzzer can stress an MCU pin.
Frequently Asked Questions
How to tell active/passive apart?+
Which to play a melody?+
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