User`s guide

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 dierent shapes and
sizes, which can be used to create sound waves when
provided with analog electrical signal. EasyMx PRO
™
v7
comes with piezo buzzer which can be connected to PA6
microcontroller pin. Connection is established using SW4.4
DIP switch. Buzzer is driven by transistor Q2 (Figure 19-1).
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.
page 33
Figure 19-2:
push
SW12.1 to
ON position
to connect
Piezo buzzer
to PA6
DATA BUS
PERSPECTIVE
VIEW
TOP
VIEW
R52
10K
Q2
BC846
R50
1K
VCC-5V
BUZZER
PZ1
BUZZER
1 2 3 4 5
6
7 8
O
N
SW12
VCC-5V
PA6
1 2 3 4 5
6
7 8
In order to use the on-board Piezo Buzzer in
your application, you rst have to connect the
transistor driver of piezo buzzer to the appropriate
microcontroller pin. This is done using SW12.1 DIP
switch which connects it to PA6 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 PA6
microcontroller pin
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%
TO SOCKETS
VCC-5V
R3
1K
PZ1
Q8
BC846
10K
R27
PERSPECTIVE
VIEW
TOP
VIEW
RE1
RC2
J21
BUZZER
TO SOCKETS
VCC-5V
R3
1K
PZ1
Q8
BC846
10K
R27
PERSPECTIVE
VIEW
TOP
VIEW
RE1
RC2
J21
BUZZER
TO SOCKETS
VCC-5V
R3
1K
PZ1
Q8
BC846
10K
R27
PERSPECTIVE
VIEW
TOP
VIEW
RE1
RC2
J21
BUZZER
Piezo Buzzer
multimedia
EasyMx PRO
v7