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PCRT21ASX Datasheet - Page 6

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Piezoelectric Acoustic Generators
Suggestions for Handling
In order to maximize the quality of piezoelectric elements,
it is necessary that proper handling procedures be used.
Do not operate or store for a long time under conditions of
high temperature and high humidity.
• Piezoelectric characteristics may degrade when kept at
more than 80 C for a long time.
• The electrodes may be shorted if a drop of water falls
onto the silver electrode area of the transducer.
Keep soldering time to a minimum.
• Soldering operation must be less than 320 C and
completed within 1.5 seconds.
• 2% silver solder for silver electrodes must be used to
prevent leaching.
• Piezoelectric acoustic elements are supplied with leads
for our customers' convenience. The specifications are
as follows:
1) Standard lead specification AWG#28 and AWG#32
(7 strand copper wires covered with red color vinyl
insulation)
2) Standard length (mm) 50, 75, 100, 125, 150
OPTION (A)
TANGENT DIRECTION
NORMAL DIRECTION
figure 13
3) How leads may be soldered:
Do not apply unnecessary weight to the element
• The transducer consists of a one hundred micron thick
metal plate and also a one hundred micron thick
ceramic plate. The ceramic plate will crack when too
much weight is applied to the device.
Mechanical Shock
• If equipment (with a piezo-electric transducer) receives
a mechanical shock, resulting in stress to the piezoelec-
tric element, an electric feedback can result, damaging
other components in the circuits.
Attention must be paid to the assembled location in order
to generate maximum sound output.
Remember that the 3-terminal type is a part of the oscilla-
tion circuit.
• Do not place a cover in front of the buzzer, if possible.
• When assembling, do not deform or bend the trans-
ducer fixture. Deformation of the transducer changes
the oscillation condition.
NOTE:
Wherever possible, the piezo devices should be
capacitive coupled to avoid permanent DC bias and possible
long term damage.
Drive Circuits
Because the impedance of the piezoelectric buzzer (2-
terminal type) is capacitive, the drive circuit can be designed
utilizing the transducer as a capacitor.
Drive circuits are classified into two types. One type is the
amplification type which amplifies and supplies input signal
(from IC, etc.) to the transducer. The other is the oscillation
type, in which the transducer constitutes a part of the circuit
together with other active elements.
Typical circuit types are as follows:
Transducer Drive Circuit
Amplification Type
OPTION (B)
Load Resistance Type
Complementary Type
Load Inductance Type
Table I
Oscillation Type
Blocking Oscillation Type
Multivibrator Type
CR Oscillation Type
3-Terminal Buzzer Type
IC Type
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