mikroElektronika EasyPIC PRO v7, User Manual

Page: 29 / 41

Piezoelectricity is the charge which accumulates in
certain solid materials in response to mechanical pressure,
but also providing the charge to the piezoelectric material
causes it to physically deform. One of the most widely
used applications of piezoelectricity is the production of
sound generators, called piezo buzzers.
Piezo buzzer is
an electric component that comes in different shapes and
sizes, which can be used to create sound waves when
provided with analog electrical signal. EasyPIC PRO
™
v7
comes with piezo buzzer which can be connected to RB6
microcontroller pin. Connection is established using
SW4.4
DIP switch. Buzzer is driven by transistor Q1 ( Figure 15-1 ).
Microcontrollers can create sound by generating a PWM
(Pulse Width Modulated) signal – a
square wave
signal,
which is nothing more than a sequence of logic zeros and
ones. Frequency of the square signal determines
the pitch of the generated sound, and duty cycle of
the signal can be used to increase or decrease the
volume in the range from 0% to 100% of the duty
cycle. You can generate PWM signal using hardware
capture-compare module, which is usually available in
most microcontrollers, or by writing a custom software
which emulates the desired signal waveform.
Supported sound frequencies
Piezo buzzer’s resonant frequency (where you can expect
it's best performance) is
3.8kHz
, but you can also use it to
create sound in the range between 2kHz and 4kHz .
Figure 15-2:
Turn ON
SW4.4 to
connect
Piezo buzzer
driver to
RB6 pin
PERSPECTIVE
VIEW
TOP
VIEW
D
AT
A BUS
In order to use the on-board Piezo Buzzer in
your application, you first have to connect the
transistor driver of piezo buzzer to the appropriate
microcontroller pin. This is done using
SW4.4 DIP
switch. Once the switch is in ON position, it connects
the buzzer driver to
RB6
microcontroller pin.
Buzzer starts "singing" when you provide
PWM signal from the microcontroller
to the buzzer driver. The pitch of the
sound is determined by the frequency,
and amplitude is determined by the
duty cycle of the PWM signal.
Enabling Piezo Buzzer
How to make it sing?
Figure 15-1: Piezo
buzzer connected to
RB6 microcontroller
pin via SW4.4
Freq = 3kHz, Duty Cycle = 50
%
Freq = 3kHz,
Volume = 50
%
Freq = 3kHz,
Volume = 80
%
Freq = 3kHz,
Volume = 20
%
Freq = 3kHz, Duty Cycle = 80
%
Freq = 3kHz, Duty Cycle = 20
%
Piezo Buzzer
page 29
other modules
Easy PIC PRO
v7