mikroElektronika EasyAVR v7, Руководство пользователя

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Figure 18-2:
Use jumper
J12 to
connect
Piezo buzzer
on PB1 or
PD4 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. EasyAVR
™
v7 comes
with piezo buzzer which can be connected either to
PB1
or
PD4
microcontroller pins, which is determined by the position
of
J21
jumper. Buzzer is driven by transistor
Q8
(
Figure 18-1
).
Microcontrollers can create sound by generating a PWM (Pulse Width
Modulated) signal – a
square wave
signal, which is nothing more than
R42
10K
Q8
BC846
R39
1K
VCC-5V
BUZZER
PB1
PD4
PZ1
BUZZER
J21
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
J21
. You can place the jumper in two positions,
thus connecting the buzzer driver to either
PB1
or
PD4
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?
page 28
Figure 18-1: Piezo
buzzer connected to PB1
microcontroller pin
Piezo Buzzer
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
%
TO SOCK
ETS
VCC-5V
R3
1K
PZ1
Q8
BC846
10K
R27
PERSPECTIVE
VIEW
TOP
VIEW
RE1
RC2
J21
BUZZER
TO SOCK
ETS
VCC-5V
R3
1K
PZ1
Q8
BC846
10K
R27
PERSPECTIVE
VIEW
TOP
VIEW
RE1
RC2
J21
BUZZER
TO SOCK
ETS
VCC-5V
R3
1K
PZ1
Q8
BC846
10K
R27
PERSPECTIVE
VIEW
TOP
VIEW
RE1
RC2
J21
BUZZER
modules
Easy AVR
v7