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Piezo Buzzer

Piezo Buzzer

Piezo buzzer includes a piezo plate attached within its plastic housing. The working principle of the piezo plate is piezo-electric effect. Input alternating Vpp signal, the piezo plate will vibrate up and down to produce sound. Piezo buzzer is voltage sensitive and insensitive to current. That is, it's voltage driven and its SPL (Sound Output Level) increases positively with voltage. Usually piezo buzzer needs at least 3V to produce enough SPL. As piezo plates can stand up to very high voltages, ex: 20V~30V, it means that the user is encouraged to boost input voltage to get louder sound. Siren, a type of piezo buzzer, plays out specific alerting tunes. The tunes are usually generated internally by the siren's default oscillation circuit, which is fed by VDC power.

If the buzzer contains oscillation circuit within it, then it's called self-driven buzzer or "indicator". If the buzzer doesn't contain any oscillation circuit, then it's called externally-driven buzzer or "transducer". The advantage of a transducer is that the user can freely design and designate input audio signal, keeping in mind that the input signal shall be around the resonant frequency to product max SPL. The advantage of an indicator is it can be easily driven by DC power, for example battery supply, but one should recognize that the output audio frequency is fixed by the internal circuit.

Piezo buzzer is better at giving out higher resonant frequency, for example 4,000hz sound. Its sound quality is harsh and it's intended to alert the user. The user is discouraged to use a piezo buzzer to play low frequencies, because low frequencies are not alerting enough and their sound volume is relatively low. The user should instead use micro-speakers to play out low frequencies or music and human voice. In some scenarios where high SPL is expected, the user might have to choose larger piezo buzzers, for example phi 30mm or phi 40mm.

Piezo buzzer usually comes with lead wire or pin, seldom with SMT. The advantage of lead wire termination is that the user can locate it freely on the housing. Piezo buzzer is resistant to shocks and is robust, which is suited in harsh environments. Due to concise and compact design, its weight is also light. Furthermore, as the piezo buzzer is capacitive, so the consumption current is low, which is best suited in power-saving applications.


 

 

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