Control buzzer based on C51

Preface ： This experiment is based on STC89C52RC Single chip microcomputer , Program and control the buzzer according to the circuit schematic . because 51 The structure of Series MCU is similar , Readers can draw inferences from this blog , Realize the required functions .

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Catalog :

• One 、 Buzzer Introduction
• Two 、 Circuit schematic analysis
• 3、 ... and 、 Realize buzzer ringing

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The single chip microcomputer selected in the experiment and its structure are displayed ( In general C51 For example , The others are similar ), The buzzer operated in this experiment is located in the serial number ⑱ Location

One 、 Buzzer Introduction

Buzzer can be divided into Active buzzer （ Including drive line ） and Passive buzzer （ External drive ）. Active and passive , It doesn't mean power , It refers to whether there is an oscillation circuit inside the buzzer , Internal oscillation circuit of active buzzer , Just provide power to sound ; The passive buzzer needs to provide a certain frequency pulse signal to sound , The frequency is usually at 1.5-5KHZ Between , The physical drawing of buzzer is shown in the figure below ：

Distinguish between active and passive buzzers ： Place the pins of the two buzzers upward , One with a green circuit board is a passive buzzer , What is closed with black glue without circuit board is an active buzzer
For passive buzzers , If you change the frequency, you can adjust the buzzer tone , Produce a variety of different timbres 、 The sound of tone . If you change the high and low level duty cycle of the output level , You can change the sound level of the buzzer

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Two 、 Circuit schematic analysis

For this experiment, we should realize the control of buzzer , We can't use SCM directly IO Mouth drive . because 51 Single chip microcomputer IO The driving ability of the port is weak ( Even if the external pull-up resistor ), The buzzer drive takes about 30mA, So it's very difficult . The buzzer module circuit on the development version used in this experiment is shown in the figure below ：

51 SCM is mainly used to control rather than drive , Using chips directly GPIO Pins to drive high-power devices , Or burn the chip , Or it won't drive . So drive high-power devices , It is necessary to build the driving circuit , The driver chip on the development board is ULN2003D. It can be seen from the above figure ,ULN2003D Control the input port of the buzzer and the P2.5 Connect , The corresponding output is OUT5. adopt ULN2003D,GPIO The pin can control the buzzer .

The buzzer used in this experiment is a passive buzzer , To make it sound , You need to input the pulse of the specified frequency , High and low levels

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3、 ... and 、 Realize buzzer ringing

To realize the sounding of passive buzzer , It is necessary to input a pulse signal with a specified frequency to the buzzer , The designated frequency of the passive buzzer is 1.5-5KHZ, Then the period is 0.2ms-66.6ms. That is, every 0.2ms-66.6ms Turn the high and low levels inside once to control the buzzer to sound .

Based on the above analysis , It is easy to program and control the buzzer to sound

/*************************************************************************************
*   Name of the experiment ： Buzzer experiment 
*   Experimental phenomena ： The buzzer sounds after downloading the program , Close after a period of time 																			  
***************************************************************************************/
#include "reg52.h"

typedef unsigned int u16;	// Redefine the default data type of the system 
typedef unsigned char u8;

sbit BEEP=P2^5;	// take P2.5 Pins are defined as BEEP

/*******************************************************************************
*  Function name        : delay_10us
*  The functionality 		 :  The time delay function ,ten_us=1 when , About time delay 10us
*******************************************************************************/
void delay_10us(u16 ten_us)
{
	while(ten_us--);	
}

void main()
{	
	u16 i=2000;

	while(1)
	{
	   	while(i--)// loop 2000 Time 
		{
			BEEP=!BEEP;// Generate a pulse signal of a certain frequency ,1ms Flip once 
			delay_10us(100);
		}
		i=0;// Zero clearing 
		BEEP=0;// Turn off the buzzer 
	}		
}

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Thank you for watching. , If you have doubts or supplements about the content , Feel free to leave a comment , Common progress ！！！