mikroElektronika EasyPIC v7, User Manual

Page: 32 / 37

Easy PIC
for dsPIC30
®
v7
page 32
Figure 19-2:
Use jumper
J12 to
connect
Piezo buzzer
on
RD0 or
RA11 pin
Piezo electricity 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 piezo electricity 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
™
v7 for dsPIC30
®
comes with piezo buzzer which
can be connected either to RD0 or RA11 microcontroller
pins, which is determined by the position of J12 jumper. Buzzer
is driven by transistor Q6 (Figure 19-1). Microcontrollers can create
sound by generating a PWM (Pulse Width Modulated) signal – a square
R24
10K
Q6
BC846
R23
1K
VCC-5V
BUZZER
J12
RA11
RD0
PZ1
BUZZER
PERSPECTIVE
VIEW
TOP
VIEW
DATA 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 jumper J12.
You can place the jumper in two positions, thus
connecting the buzzer driver to either RD0 or RA11
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 19-1: Piezo
buzzer connected to RD0
microcontroller pin
Piezo Buzzer
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.
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
%
other modules
R24
10K
Q6
BC846
R23
1K
VCC-5V
BUZZER
J12
RA11
RD0
PZ1
BUZZER
PERSPECTIVE
VIEW
TOP
VIEW
DATA BUS
R24
10K
Q6
BC846
R23
1K
VCC-5V
BUZZER
J12
RA11
RD0
PZ1
BUZZER
PERSPECTIVE
VIEW
TOP
VIEW
DATA BUS
R24
10K
Q6
BC846
R23
1K
VCC-5V
BUZZER
J12
RA11
RD0
PZ1
BUZZER
PERSPECTIVE
VIEW
TOP
VIEW
DATA BUS