Table of Contents
22 MM Flash LED Alarm Indicator Light Signal Lamp Flash Metal Hand Buzzer DC12V DC24V AC 220V Intermittent Sound
(1) Introduction of metal buzzer
1. The role of a metal hand buzzer is an integrated structure of an electronic buzzer, using DC voltage power supply, widely used in computers, printers, copiers, alarms, electronic toys, automotive electronic equipment, telephones, timers used as a sounding device in electronic products.
2 Classification of metal hand buzzer is mainly divided into two types: piezoelectric metal hand buzzer and electromagnetic metal buzzer.
3. The circuit graphic symbol of metal hand buzzer in the circuit with letters “or “HAT old standard with “FMLB” JD” etc.) said.
(2) Structural principle of metal buzzer
1. Piezoelectric metal buzzer is mainly composed of the multivibrator, piezoelectric buzzer, impedance matcher, resonance box, shell and so on. Some piezoelectric metal hand buzzer shells are also equipped with light-emitting diodes.
The multivibrator is composed of transistors or integrated circuits. When the power is turned on (1.5~15V DC working voltage), the multivibrator starts to vibrate and outputs 1.5~25kHz audio signals, and the impedance matcher drives 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 the stainless steel sheet.
2. Electromagnetic metal hand buzzer The electromagnetic metal hand buzzer is composed of the oscillator, an 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.
How does the conventional electromagnetic metal hand buzzer product work?
The working principle of the passive electromagnetic metal hand buzzer is: the AC signal generates an alternating magnetic flux on the core column of the support through the wire wrapped around the support. The alternating magnetic flux and the constant magnetic flux of the magnetic ring are superimposed to make the molybdenum The sheet vibrates at a given frequency of the AC signal and cooperates with the resonant cavity to produce sound.
The response curve and gap value of the entire frequency and sound pressure of the product, the natural vibration frequency of the molybdenum sheet (which can be roughly refracted to the thickness of the small molybdenum sheet), the frequency of the shell (Helmholtz resonance acoustic cavity), and the magnetic enameled wire of the magnetic ring The wire diameter is directly related.
(3) How do conventional piezoelectric metal buzzer products work?
The piezoelectric buzzer is a piezoelectric ceramic sheet that has been subjected to high-voltage extreme pressure and is pasted on a vibrating metal sheet. When an AC voltage is added, it will generate mechanical deformation and contraction due to the piezoelectric effect, and use this feature to make the metal sheet vibrate and make a sound
1. Peripheral support method-fix the outer diameter edge of the buzzer in the resonant cavity, generally a non-feedback buzzer, and the buzzer must be matched with the resonant cavity frequency to have a higher sound pressure output, And an external oscillator circuit generates a push signal to make the metal hand buzzer sound.
Node support method-fix the buzzer sheet in a ring structure approximately the same size as the diameter of the ceramic sheet. If the resonant cavity is properly designed, combined with a feedback buzzer with the correct frequency and a positive feedback circuit, larger sound pressure and correct frequency can be generated.
(4) What materials are made of conventional piezoelectric passive metal hand buzzer (external drive) products?
PCB fixed piezoelectric passive
Pogo pin piezoelectric passive metal buzzer
(5) What is the difference between an active metal hand buzzer and a passive metal hand buzzer?
The fundamental difference between an active metal hand buzzer and a passive metal hand buzzer is that the product has different requirements for input signals;
The ideal signal for an active metal hand buzzer is direct current, usually marked as VDC, VDD, etc. Because there is a simple oscillating circuit inside the metal hand buzzer, it can convert a constant direct current into a pulse signal of a certain frequency, and the alternating magnetic field is generated from the surface, which drives the molybdenum sheet to vibrate and pronounce.
However, some active metal hand buzzers can also work under a specific AC signal, but the voltage and frequency of the AC signal are very demanding, and this working method is generally not used.
The passive metal buzzer has no internal driving circuit. Some companies and factories call it a buzzer, and it is called a buzzer in the national standard.
Ideal signal square wave for passive metal hand buzzer work. If the metal hand buzzer is not responding to the pre-DC signal, because the magnetic circuit is constant, the molybdenum sheet cannot vibrate and sound.
(6) How to connect the electromagnetic passive metal hand buzzer and piezoelectric passive metal hand buzzer to the IC output pins in the electronic circuit?
The electromagnetic passive buzzer is an inductive load device, and the ideal input is a forward square wave, usually denoted as VO-P. Usually, the wiring circuit is as follows:
The passive buzzer is a capacitive load device, and the ideal input is a two-way square wave, usually denoted as VP-P. Usually, the wiring circuit is as follows:
But if the IC is an inverter 4049, etc., it is also ideal to connect the input and output of a NOT gate to a metal hand buzzer, but sometimes the output power of the IC is too small and the sound cannot meet the expected requirements.
If the metal hand buzzer is used for high sound pressure alarms, ordinary two-pin inductors cannot meet the requirements. Generally, three-pin tapped inductors are generally used with a boost ratio of 10 times. Some high sound pressures above 110dB may need to be used. The power transformer realizes the step-up.
(7) Production of metal hand buzzer
(1) Preparation of electromagnet M: Wind 100 turns of wire on an iron bolt about 6 cm in length, 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 paperclip as the contact Q, use a book to put the paperclip up high, glue it firmly with tape, and draw out 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 just touch, and you can hear the buzzing sound after power on.
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