supplied with the kit
available in the Nuts &
Figure 7 shows the
speaker and circuit ready
to go. I used an iPod for
the audio source for the
circuit. (The iPod is NOT
included in the kit.)
■ FIGURE 5. Schematic of
piezoelectric speaker project.
speaker measures three inches by six inches.
While the material does change dimensionally across
its length, it is to a lesser degree as the dipoles are mostly
aligned perpendicular to its thickness.
To use this material as a speaker, it is necessary to provide
a high voltage audio signal. This is accomplished by feeding
a standard audio signal through a step-up transformer.
Referring to the schematic in Figure 5, an electrical
audio signal from a radio or iPod is applied to the input
header P1. The signal feeds through a voltage divider
network composed of resistor R4 and potentiometer V1.
The signal from V1 feeds into the LM386 audio amplifier
IC. V1 acts as a volume control. The LM386 is set up in a
standard configuration to produce a gain of 50X
The output of the audio amplifier is fed to the primary
of a mini step-up transformer. The high voltage output
from the transformer is fed to the piezoelectric film speaker.
Figure 6 is a close-up of the circuit built on a PCB
Mount and solder the
HV transformer making
sure to line up the yellow
dot on the transformer to
the silkscreen dot on the
transformer outline. Mount and solder (V1) 10K
potentiometer PC mount (R3 and R4) 390 ohm 1/4 watt
resistor; R1 1.2K ohm 1/4 watt resistor; R2 10 ohm 1/2
watt resistor; C1 and C4, 10 µF capacitors; C2, .047 µF
capacitor; and C3, a 200-250 µF capacitor. Mount and
solder slide switch S1. The input P1 and piezo speaker
outputs are two-pin female sockets. Mount and solder into
place. Plug the LM386 in the eight-pin socket. Orientate
the indent on the IC to the indent on the silkscreen.
Connect your audio source to the input header. Turn
it on and set its volume range mid-point. Connect the
piezoelectric film speaker to the output. Turn on the
circuit and adjust the V1 volume control until you hear
sound coming out of the speaker.
By curving the speaker, the sound volume increases. If
■ FIGURE 6. Photo of piezoelectric film speaker built on a PCB.
■ FIGURE 7. All the components of the system: circuit,
speaker, and audio source.