1. The role of the buzzer The buzzer is an integrated structure of electronic signals, using DC voltage power supply, widely used in computers, printers, photocopiers, alarms, electronic toys, automotive electronics, telephones, timers, and other electronic products for the sound device.
2. Buzzer classification Buzzer is mainly divided into piezoelectric buzzer and electromagnetic buzzer two types.
3. Buzzer circuit graphic symbols Buzzer in the circuit with the letter "H" or "HA" (the old standard with "FM".), "LB", "LB", "LB", "LB", "LB", "LB", "LB", "LB", "LB", "LB", "LB" and so on, "LB", "JD", etc.).
(B) the structural principle of the buzzer
1. piezoelectric buzzer piezoelectric buzzer is mainly composed of a polytunnel oscillator, piezoelectric buzzer, impedance matching and **** sound box, shell and so on. Some piezoelectric buzzer shell is also equipped with light-emitting diodes.
Multi-tuned oscillator is composed of transistors or integrated circuits. When the power supply (1.5 ~ 15V DC operating voltage), multi-harmonic oscillator vibration, output 1.5 ~ 2.5kHZ audio signal, impedance matching device to promote the piezoelectric buzzer sound.
The piezoelectric buzzer is made of lead zirconate titanate or lead niobium magnesium piezoelectric ceramic material. Silver electrodes are plated on both sides of the ceramic sheet, which are polarized and aged, and then glued together with a brass or stainless steel sheet.
2. Electromagnetic buzzer Electromagnetic buzzer consists of an oscillator, electromagnetic coil, magnet, vibrating diaphragm and shell.
After turning on the power supply, the oscillator generates the audio signal current through the electromagnetic coil, so that the electromagnetic coil generates a magnetic field. Vibrating diaphragm in the electromagnetic coil and magnet interaction, periodic vibration sound.
Buzzer production
(1) Preparation of the electromagnet M: in the length of about 6 centimeters on the iron bolt around 100 turns of wire, the end of the line left 5 centimeters for the lead, with transparent tape to the coil is well glued so as not to loosen the coil, and then use the tape to stick it on a box, the electromagnet is done.
(2) the preparation of shrapnel P: from the tin can box cut a long piece of iron about 2 centimeters wide, bent at a right angle, the electromagnet of a lead connected to the shrapnel, and then tape the shrapnel tightly on the board.
(3) use a pin as a contact Q, use a book to cushion the pin, with tape, lead a wire, as shown in the figure to connect the circuit.
(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 contact and the shrapnel, so that they can be exactly in contact with the beeping sound can be heard after the power is turned on
Speakers are divided into built-in speakers and external speakers, and the external speakers that is, generally referred to as the speaker. Built-in speaker means that the MP4 player has a built-in speaker, so that users can not only through the headphone jack can also be through the built-in speaker to listen to the MP4 player sound. MP4 players with built-in speakers can avoid the inconvenience of having to wear headphones for a long time without external speakers.
Physical significance of the common parameters of the speaker:
The parameters of the speaker refers to the use of a dedicated speaker test system to test out the specific performance parameters of the speaker. Its common
parameters include: Z, Fo, η0,
SPL, Qts, Qms, Qes, Vas, Mms, Cms, Sd, BL, Xmax, Gap gauss. The following are the physical significance of these parameters.
1.1 Z: refers to the resistance of the speaker, including: rated impedance and DC impedance. (Unit: ohm/ohm), usually refers to the rated impedance.
The rated impedance of a loudspeaker, Z, is the smallest impedance modulus behind the first maximum value of the impedance curve, i.e., the impedance value corresponding to point B in Figure 1.
It is the basis for calculating the electrical power of the speaker.
DC impedance DCR: It is the impedance value of the voice coil when the coil is static and a DC signal is passed through it.
We usually say 4 ohm or 8 ohm is the rated impedance.
1.2 Fo (lowest **** vibration frequency) is the frequency that corresponds to the first maximum value of the impedance curve of the speaker.
Unit: Hertz (Hz).
The impedance curve of a loudspeaker is a loudspeaker under normal operating conditions, with constant current or constant voltage method to measure the impedance modulus of the loudspeaker with the frequency
change curve.
1.3 η0 (loudspeaker efficiency): refers to the ratio of the loudspeaker output acoustic power to the input electric power.
1.4 SPL (sound pressure level): refers to the speaker in the rated impedance of 1W of electric power voltage, in the reference axis and the speaker at a distance of 1m points
produced sound pressure. Unit: decibel (dB).
1.5 Qts :The value of the total quality factor of the loudspeaker.
1.6 Qms: the mechanical quality factor of the loudspeaker.
1.7 Qes: the electrical quality factor value of the loudspeaker.
1.8 Vas (effective volume of the loudspeaker): is the volume of air in a rigid container when the acoustic compliance of the air is equal to the acoustic compliance of the loudspeaker unit
. Unit: liter (L).
1.9 Mms (vibrational mass): is the sum of the mass of the parts of the loudspeaker that participate in the vibration of the process of movement, including the paper part of the drum, the voice coil, the spring wave
and the mass of the air involved in the vibration and so on. The unit is gram.
1.10 Cms (force smooth): refers to the smoothness of the supporting components of the speaker vibration system. The larger the value, the softer the speaker's entire vibration system. Single
Bit: mm/Newton (mm/N).
1.11 Sd (vibration area): refers to the vibration process in the speaker, the effective vibration area of the drum paper / diaphragm. Unit: square meters (m2).
1.12 BL (magnetic force): the product of the gap magnetic induction and the effective voice coil line length. Unit: (T*M).
1.13 Xmax: the linear travel of the voice coil during vibration. Unit: millimeter (mm).
1.14 Gap Gauss: the value of the gap magnetic induction. Unit: Tesla (Tesla).
From the above, we can see that the principle is almost the same, the difference is that the former use reeds to vibrate directly, the latter is a coil in the vibration of the paper pots, a low frequency requirements of a high technical requirements of the former is simpler, the latter is more complex structure in turn
1.14 Gap Gauss: the value of the magnetic induction of the gap.