Figure 4-8 Piezoelectricity - Fujitsu F2MC-8FX Series User Manual

Next, here explains how to output buzzer sounds.
An element called a piezoelectric element is used in the buzzer. Piezoelectric elements are elements
that use the piezoelectric effect, and which use materials that create a voltage when shock or pressure
are applied (piezoelectricity) or, conversely, which use materials with properties that create a
distortion in the crystal configuration when a voltage is applied (reverse piezoelectricity).As shown
in "Figure 4-8 Piezoelectricity", piezoelectric elements have the property of expanding when a
voltage is applied in the direction of polarization (the direction of the green arrows) and contracting
when a voltage is applied in the opposite direction to polarization (the opposite direction from the
green arrows).
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Consequently, as shown in "Figure 4-9 Principle of piezoelectric elements", when an AC voltage is
applied, the crystals repeatedly expand and contract each time the direction of the voltage alternates.
By changing the frequency of the AC voltage, the speed of the crystal contraction and expansion also
changes. If this property is used skillfully, the crystal can be vibrated at various frequencies. If the
vibration energy of the crystal is sufficiently great, it can also vibrate the air to create sound. This is
the principle used in the piezoelectric buzzer.
膨張
Expansion

Figure 4-8 Piezoelectricity

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収縮
Contraction
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