1.
The function of the buzzer: the buzzer is an integrated structure of
the electronic buzzer, powered by a DC power supply, and is widely used
in computers, printers, copiers, alarms, electronic toys, automotive
electronic equipment, telephones, timers, etc. Used as a sounding device
in electronic products.
2. Buzzer classification: mainly divided into two types: piezoelectric buzzer and electromagnetic buzzer.
3. The circuit graphic symbol of the buzzer: the buzzer is represented
by the letter "H" or "HA" in the circuit (the old standard uses "FM",
"LB", "JD", etc.).
(2) The structure principle of the buzzer
1. Piezoelectric buzzer: The piezoelectric buzzer is mainly composed of a
multivibrator, a piezoelectric buzzer, an impedance matcher, a
resonance box, and a shell. Some piezoelectric buzzers are also equipped
with light-emitting diodes.
Multivibrator is composed of transistors or integrated circuits. When
the power is turned on (1.5V-15V DC working voltage), the multivibrator
will vibrate and output 1.5-2.5kHZ audio signals, and the impedance
matcher will drive the piezoelectric buzzer to sound.
The piezoelectric buzzer is made of lead zirconate titanate or lead
magnesium niobate piezoelectric ceramic material. Silver electrodes are
plated on both sides of the ceramic sheet, and after polarization and
aging treatment, they are then glued together with the brass sheet or
stainless steel sheet.
2. Electromagnetic buzzer: The electromagnetic buzzer is composed of
oscillator, electromagnetic coil, magnet, vibrating diaphragm and shell.
After the power is turned on, the audio signal current generated by
the oscillator passes through the electromagnetic coil, causing the
electromagnetic coil to generate a magnetic field. The vibrating
diaphragm periodically vibrates and produces sound under the interaction
of the electromagnetic coil and the magnet.
(3) Making of the buzzer
(1) Preparation of electromagnet M: Wind 100 turns of wire on an iron
bolt with a length of about 6 cm, leaving 5 cm at the end of the wire as
a lead, and stick the coil with transparent tape to prevent the coil
from loosening, and then stick it with tape On a box, the electromagnet
is ready.
(2) Preparation of shrapnel P: Cut a long iron piece with a width of
about 2 cm from the iron can, bend it at a right angle, connect a lead
of the electromagnet to the shrapnel, and then use tape to stick the
shrapnel on the wooden board.
(3) Use a paper clip as the contact Q, put the paper clip up high
with a book, glue it firmly with tape, and lead out a wire. Connect the
circuit as shown in the figure.
(4) Adjust the distance between M and P (by moving the box), so that
the electromagnet can attract the shrapnel, adjust the distance between
the contacts and the shrapnel, so that they can just touch, and you can
hear the buzzing sound after power on.
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