[single chip microcomputer] [make buzzer sound] know the buzzer and let it make the sound you want

The buzzer in the single chip microcomputer

1. triode

Triode is a semiconductor device that controls current , The function is to amplify the weak signal into an electrical signal with large amplitude value （ Radio frequency method ）, Also used as contactless switch （ Used as a switch ）.

Simply speaking , Triode has the function of current amplification .

Triode is called semiconductor triode , Or bipolar transistor 、 Crystal triode , There are two packaging methods ： Plug in and chip mount .

The working principle of triode ： There are two kinds of circuit arrangement inside the triode , One is PNP type , One is NPN type , The only difference between the two is that the current flows in different directions .

The triode has three pins , Namely BASE( The base )、EMITTER( The emitter )、COLLECTOR( Collector ). The internal circuit of the triode is as follows , On the left is NPN type , On the right is PNP type .

 PNP type ： When B extremely （ The base ） The current is greater than 1mA when , Or when the base voltage is less than the emitter voltage , Conduction between collector and emitter , There's electricity going through .

NPN type ： When the base potential is a few tenths of a volt higher than the emitter , The emitter junction is in a positive bias state , When the collector potential is several volts higher than the base potential , The collector junction is in the reverse bias state , The collector power supply should be higher than the base power supply .

about NPN tube , It is from 2 block N There is a piece of semiconductor in the middle P Composed of semiconductor , Formed between the emission region and the base region PN A knot is called a launch knot , The collector area and the base area form PN A junction is called a collector junction ,

 2. Know the buzzer

The buzzer on the single chip microcomputer is as follows , The green circuit board on the left is the active buzzer , The passive buzzer is sealed with black glue on the right .

According to whether it contains Oscillating circuit , Buzzer can be divided into active buzzer and passive buzzer .

The active buzzer is directly controlled by the high and low levels , The passive buzzer needs a certain frequency of pulse to trigger sound .

The electromagnetic buzzer consists of an oscillator 、 Electromagnetic coil 、 Magnets 、 It is composed of vibrating diaphragm and shell . How it works ： When the power is on , The current of the audio signal generated by the oscillator passes through the electromagnetic coil , Make the electromagnetic coil produce a magnetic field , The vibrating diaphragm is under the interaction of electromagnetic coil and magnet , Periodically vibrate and sound . The buzzer has an oscillation circuit , It belongs to active buzzer .

Piezoelectric buzzer is mainly composed of multivibrator 、 Piezoelectric buzzer 、 Impedance matchers and resonators 、 The enclosure lamp consists of . How it works ： A multivibrator consists of a transistor or an integrated circuit , When the power is on （1.5V~15V DC operating voltage ）, The multivibrator starts , Output 1.5~2.5kHz The audio signal , The impedance matching device pushes the piezoelectric buzzer to sound . The buzzer belongs to a passive buzzer .

The buzzer can only work by amplifying the driving current through the amplifying circuit .

For passive buzzers ,

Change the frequency of the output waveform of the MCU pin , The control buzzer tone can be adjusted , Produce a variety of different timbres 、 The sound of tone ;
The high and low level duty cycle of the Centennial output level , It can control the sound level of the buzzer .

3. ULN2003 A brief introduction to the chip

As mentioned earlier, the buzzer needs to pass the amplifying circuit to make sound , stay 【 Puzhong 51- Single core -A2 The board 】 On , Use ULN2003 The chip amplifies the current .

ULN2003 High voltage resistance 、 High Current Darlington display , It's made of seven silicon NON Darlington tube composition .

ULN2003 It's a high current drive array , It is mostly used for single chip microcomputer 、 Smart meters 、PLC、 Digital output card lamp control circuit , The buzzer can be driven directly 、 Relay and other loads .

4. Buzzer related circuit

The buzzer is connected to through an amplifying circuit P1^5, By controlling P1^5 The high and low levels of the port form a pulse , Trigger the buzzer to sound .

sbit beep = P1^5;
void ring_buzzer()
{
	beep = 0;
	while(1)
	{
		beep = ~beep;
		delay_ms(100);
	}	
}

Integrated application with running water lamp , Make a running water lamp , The light is on and the buzzer makes a sound

/************************************************************
 P1 Mouth to mouth 8 individual LED, Co anode ,P37 Connected to buzzer 
  Make a running water lamp , The light is on and the buzzer makes a sound 
************************************************************/
#define LEDP1	P1
sbit beep = P3^7;
void led_p1_beep_p37()
{	
	u8 i=0;
	u16 delay_times = 10000;  // 200ms
	//  The initial state 
	P1 = ~0x01;
	delay_ms(delay_times);
	while(1)
	{
		for(i=0;i<7;i++)
		{
			P1 = _crol_(P1,1);  //  The left one 
			beep = ~beep;
			delay_ms(delay_times);	
		}
		for(i=0;i<7;i++)
		{
			P1 = _cror_(P1,1);  //  The left one 
			beep = ~beep;
			delay_ms(delay_times);	
		}
	}	
}

​​​​​​​Proteus Simulation display results ：

 5. Use the buzzer to make music

Reference resources ：STC89C52 MCU buzzer introduction and 《 Lone brave 》 Song code example _ Avocado loves to eat piglets -CSDN Blog _51 MCU buzzer music code