Active buzzer and passive buzzer difference

Introduction and identification of active and passive buzzers (driver/circuit) Note that the “source” here does not refer to the power supply. It refers to the source of the shock. In other words, the active buzzer has an internal source of oscillation, so it will be called as soon as it is energized.

There is no source of oscillation inside the passive, so if you use a DC signal, you can't make it scream. It must be driven by a square wave of 2K~5K. Active buzzers tend to be more expensive than passive ones because of the multiple oscillating circuits inside.

The advantages of passive buzzer are: 1. Cheaper 2. The frequency of the sound is controllable, and you can make the effect of “More than Ms. Sola”. In some special cases, a control port can be multiplexed with the LED

The advantage of the active buzzer is: Program control is convenient

A) Introduction of the buzzer 1. The buzzer is an integrated electronic sounder that is powered by DC voltage and is widely used in computers, printers, copiers, alarms, electronic toys, automotive electronics, telephones, timers, etc. Sounding device in the product. 2. Classification of buzzer Buzzer is mainly divided into two types: piezoelectric buzzer and electromagnetic buzzer. 3. The circuit symbol of the buzzer The buzzer is represented in the circuit by the letters “H” or “HA”” (the old standard is “FM””, “LB”, “JD”, etc.). (B) the structure of the buzzer 1. Piezoelectric Buzzer The piezoelectric buzzer is mainly composed of a multivibrator, a piezoelectric buzzer, an impedance matching device, a resonance box, and an outer casing. Some piezoelectric buzzer housings are also equipped with light-emitting diodes. A multivibrator is composed of a transistor or an integrated circuit. When the power is turned on (1.5~15V DC working voltage), the multivibrator starts to oscillate and outputs an audio signal of 1.5~2.5kHZ, and the impedance matching device pushes 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 adhered to the brass sheet or the stainless steel sheet. 2. Electromagnetic buzzer The electromagnetic buzzer consists of an oscillator, an electromagnetic coil, a magnet, a diaphragm, and a casing. 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 the sound under the interaction of the electromagnetic coil and the magnet. Production of Buzzer (1) Preparation of Electromagnet M: Wrap 100 turns of wire on an iron bolt of about 6 cm in length, leaving 5 cm as a lead at the end of the wire, and stick the coil with a transparent tape to prevent the coil from loosening. Stick it to a box with tape and the electromagnet is ready. (2) Prepare the shrapnel P: Cut a long piece of iron about 2 cm wide from the canned box, bend it into a right angle, and put a piece of electromagnet The lead wire is attached to the shrapnel, and the elastic piece is attached to the wooden board with a tape. (3) Use the paper clip to make the contact Q, use the book to put the paper clip high, stick it with the tape, and lead a wire, 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 contact and the shrapnel so that they can just touch, and the buzzer can be heard after being energized. Active buzzer and passive buzzer teach you to distinguish between active buzzer and passive buzzer. A small buzzer currently on the market is small in size (only llmm in diameter), light weight, and price. Low, reliable structure, and widely used in a variety of electrical equipment, electronic production and microcontroller circuits that require sound. The appearance of the active buzzer and passive buzzer is shown in Figures a and b. Figure: Appearance of active and passive buzzers

From the appearance of figures a and b, the two buzzers look the same, but look closely The height of the two is slightly different, the active buzzer a has a height of 9 mm, and the passive buzzer b has a height of 8 mm. When placing the pin counts of the two buzzers up, it can be seen that one type of green circuit board is a passive buzzer, and one type without a circuit board and closed with black glue is an active buzzer. . To further judge the active buzzer and passive buzzer, you can also use the multimeter resistance file Rxl file test: use the black pen to connect the buzzer "+" pin, the red test pen touches the other pin Touch, if the trigger is humming, humming and the resistance is only 8 & Omega; (or 16 & Omega;) is a passive buzzer; if it can emit continuous sound, and the resistance is more than a few hundred ohms, it is an active buzzer .

The active buzzer is connected directly to the rated power supply (the new buzzer is marked on the label) for continuous sounding; the passive buzzer is the same as the electromagnetic speaker. Sound can be produced in the audio output circuit.

Classic buzzer driver:

void beep(uchar x,uchar L){beeptimes=2x-1;//The ringing once contains a pause of beepLong=L;beepcount=0;cbuz =1;}

void beepout(){if((beepcount>=beepLong)&&(beeptimes>0)){beepcount=0;beeptimes--;cbuz ^=1; }elsebeepcount++;

if(beeptimes==0) ​​cbuz=0;}