Design of smoke temperature, humidity and formaldehyde monitoring based on single chip microcomputer

Catalog

【 Function is introduced 】

【 Schematic diagram 】

【PCB】

【 A physical picture 】

【 List of components 】

【 Source program 】

 【 Principle introduction 】

【 reference 】

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【 Function is introduced 】

         This system uses single chip microcomputer as the control core , In order to realize the basic control function of portable temperature, humidity and formaldehyde detector . The main functions of the system include ： Data processing 、 Start measurement 、 Over standard alarm 、 Keyboard detection . The design of this system adopts the design idea of function modularization , The system is mainly divided into overall scheme design 、 Three parts of hardware and software design .

         This design mainly realizes the design of formaldehyde detector , Features include ： smoke 、 Temperature and humidity 、 Formaldehyde detection 、 Over standard alarm 、 Keyboard detection 、 Data display, etc .

【 Schematic diagram 】

 

【PCB】

 

【 A physical picture 】

 

【 List of components 】

specifications	name	label	Number
KEY1	Key	K1, K2, K3	3
S8050	triode	Q2	1
10K	resistance	R3	1
1K	resistance	R4	1
10K	Potentiometer	RT1, RT3	2
LCD1602	liquid crystal	U1	1
POW	Power Supply	U2	1
SWITCH	switch	U3	1
DHT11	Temperature and humidity sensor	U4	1
STM32 nucleus	Single chip microcomputer	U5	1
MQ-2	smoke	U6	1
bee	Buzzer	U9	1
CON4	formaldehyde	U34	1

【 Source program 】

#include "led.h"
#include "delay.h"
#include "sys.h"
#include "adc.h"
#include "timer.h"
#include "usart1.h"
#include "usart3.h"
#include "LCD1602.h"
#include "string.h"
#include "stdio.h"
#include "dht11.h"
#include "stmflash.h"

#define WriteFlashAddress	((u32)0x08010000)// Read and write start address 

u16 CH20_MAX_val = 100;// Formaldehyde alarm value 
u16 CH2O_mgvalue = 0;// formaldehyde 

void Change_data_handle(void);
void  SHOW_AND_BAOJING_Handle(void);
u8 KEY_SCAN(void);             // Key function 

u8 SHOW_BUF[16],SEND_BUF[16];
u8 key,PPM,Temperature,HUM;
u16 PPM_MAX=60,Temperature_MAX=40,HUM_MAX=70;// Initial value of upper limit of smoke temperature and humidity 
u16 write_buf[5];

/// Serial port correlation 
extern char RxCounter,Usart1RecBuf[64];// A serial port 1 Receive data cache 
extern char bUsart1RecFlag;   // A serial port 1 Received data flag bit 

void save_data()// Store the data 
{
	  write_buf[0]=1111;
		write_buf[1]=PPM_MAX; 
		write_buf[2]=Temperature_MAX;
		write_buf[3]=HUM_MAX;
		write_buf[4]=CH20_MAX_val;
	  STMFLASH_Write(WriteFlashAddress,write_buf,5);
}

void read_data()// Reading data 
{
	  static u16 chcek = 0;
	  STMFLASH_Read(WriteFlashAddress,write_buf,5);
	  chcek = write_buf[0];
	  if(chcek != 1111)// When the SCM is first used ,chcek It's not equal to 1111, The following is to save the data , Read again 
		{
				save_data();
			  delay_ms(100);
			  STMFLASH_Read(WriteFlashAddress,write_buf,5);
		}
	
		PPM_MAX = write_buf[1];// Upper limit of smoke 
		Temperature_MAX = write_buf[2];// Upper temperature limit 
		HUM_MAX = write_buf[3];// Upper limit of humidity 
		CH20_MAX_val = write_buf[4];//PM Upper limit value 
		
		if(PPM_MAX > 99 || PPM_MAX<0)PPM_MAX=60;
		if(Temperature_MAX > 99 || Temperature_MAX<0)Temperature_MAX=40;
		if(HUM_MAX > 99 || HUM_MAX<0)HUM_MAX=70;
		if(CH20_MAX_val > 999 || CH20_MAX_val<0)CH20_MAX_val=100;
}

void Get_CH2O(void)// Get formaldehyde 
{
    char i = 0;

		if(Usart1RecBuf[i+5] == Usart1RecBuf[i]+Usart1RecBuf[i+1]+Usart1RecBuf[i+2]+Usart1RecBuf[i+3]+Usart1RecBuf[i+4])// check 
		{
				CH2O_mgvalue = Usart1RecBuf[1]*256 + Usart1RecBuf[2];// Calculate formaldehyde 
				bUsart1RecFlag = 0;	
		}
		RxCounter = 0;
}

int main(void)
{	
  u16 test,test_adc;
	
	delay_init();	    	 // Delay function initialization 	  
	NVIC_Configuration(); 	 // Set up NVIC Interrupt grouping 2:2 Bit preemption priority ,2 Bit response priority 
	KEY_IO_Init();       
  Usart1_Init(9600);// A serial port 3 initialization , Baud rate 9600
	TIM2_Int_Init(1000,72-1);  // Timer initialization , timing 1MS
	read_data();// Start up and read the stored value once 
	delay_ms(300);
  DHT11_Init();	//DHT11 initialization 
  BEEP_DISENABLE();   // Buzzer initialization 
	LCD_Init();          // 1602 initialization  
	Adc_Init();  //ADC initialization 

  while(1)
	{
			test_adc = Get_Adc_Average(ADC_Channel_9,20);// Read channel 9 Of AD value ,20ms Read once 
			PPM = test_adc*99/4096;//12 position AD, hold AD Values are converted to percentages 0~99
			PPM = PPM >= 99? 99: PPM;// The maximum value cannot exceed 99
		  DHT11_Read_Data(&Temperature,&HUM);// Read the temperature and humidity values 
		  Get_CH2O();// Get formaldehyde value 
			SHOW_AND_BAOJING_Handle();
      Change_data_handle();// Press the key to adjust 
			delay_ms(100);
  }
}


extern u8 FLICKER;

void  SHOW_AND_BAOJING_Handle(void)
{
    unsigned char show_buf[16];// Show cache 
	  
	  if(Temperature >= Temperature_MAX)// Temperature out of limit 
		{
			 if(FLICKER)// The over limit display flashes 
			 {
					LCD_Write_String(0,0,"         ");
			 }
			 else
			 {
					sprintf(show_buf,"TEMP:%02dC",(u16)Temperature);// Convert the display format to TEMP:00C
					LCD_Write_String(0,0,show_buf);// Show 
			 }
		}
		else
		{
			sprintf(show_buf,"TEMP:%02dC",(u16)Temperature);// Convert the display format to TEMP:00C
			LCD_Write_String(0,0,show_buf);// Show 
		}
		if(HUM >= HUM_MAX)// Humidity exceeds the limit 
		{
			 if(FLICKER)// The over limit display flashes 
			 {
					LCD_Write_String(9,0,"       ");
			 }
			 else
			 {
					sprintf(show_buf,"HUM:%02d%%",(u16)HUM);// Convert the display format to HUM:00%
					LCD_Write_String(9,0,show_buf);// Show 
			 }
		}
		else
		{
			sprintf(show_buf,"HUM:%02d%%",(u16)HUM);// Convert the display format to HUM:00%
			LCD_Write_String(9,0,show_buf);
		}

		if(PPM >= PPM_MAX)// Smoke out of limit 
		{
			 if(FLICKER)// The over limit display flashes 
			 {
					LCD_Write_String(0,1,"      ");
			 }
			 else
			 {
					sprintf(show_buf,"YW:%02d%%",PPM);// Convert the display format to SMOKE:00%
					LCD_Write_String(0,1,show_buf);
			 }
		}
		else
		{
			sprintf(show_buf,"YW:%02d%%",PPM);// Convert the display format to SMOKE:00%
			LCD_Write_String(0,1,show_buf);
		}
		
		if(CH2O_mgvalue >= CH20_MAX_val && FLICKER)// Formaldehyde exceeds the limit 
		{
					LCD_Write_String(7,1,"         ");
		}
		else
		{
					
				  LCD_Write_Char(7,1,CH2O_mgvalue/100+'0');
				  LCD_Write_Char(8,1,'.');
				  LCD_Write_Char(9,1,CH2O_mgvalue%100/10+'0');
				  LCD_Write_Char(10,1,CH2O_mgvalue%10+'0');
				  LCD_Write_Char(11,1,'m');
				  LCD_Write_Char(12,1,'g');
				  LCD_Write_Char(13,1,'/');
				  LCD_Write_Char(14,1,'m');
				  LCD_Write_Char(15,1,'3');
		}
    if(Temperature >= Temperature_MAX || HUM >= HUM_MAX || PPM >= PPM_MAX || CH2O_mgvalue >= CH20_MAX_val)// Temperature, humidity, smoke and formaldehyde exceed the limit 
		{
				BEEP_ENABLE(); // Buzzer alarm 		
		}			
		else 
		{
				BEEP_DISENABLE();
		}			
}

u8 KEY_SCAN(void)
{
	  u8 res = 0;
    if(!KEY1)
		{
		   delay_ms(10);
			 if(!KEY1)
		   {
					while(!KEY1);// stuck 
					res = 1;		 
		   }
		 }
    if(!KEY2)
		{
		   delay_ms(10);
			 if(!KEY2)
		   {
					while(!KEY2);// stuck 
					res = 2;		 
		   }
		 }
    if(!KEY3)
		{
		   delay_ms(10);
			 if(!KEY3)
		   {
					while(!KEY3);// stuck 
					res = 3;		 
		   }
		 }		 
		 return res;
}

This paper introduces the key points in the design process , For your reference , If you have errors or don't understand, you can directly write to the author , Or add wechat biyezhan007.

Other information

 

【 Principle introduction 】

Working principle of smoke sensor ：

         Smoke sensor is used to detect the smoke concentration in the current place to achieve fire prevention , Ionic smoke sensor is used inside the smoke alarm , It is widely used in various fire alarm systems , Ion smoke sensor is a kind of stable and reliable , Technologically advanced sensors , The performance of fire alarm is better than that of gas sensitive resistor .

         Smoke sensors are currently divided into 2 Categories: , They are ionic smoke sensors 、 Photoelectric smoke sensor and gas sensitive smoke sensor . Photoelectric smoke sensors are divided into light reducing and light scattering photoelectric smoke detectors . This design adopts the common gas sensitive smoke sensor , Its working principle is to use tin oxide with low conductivity in clean air , When there is combustible gas in the environment where the sensor is located , The conductivity of the sensor is linearly proportional to the gas concentration , Through the SCM itself AD Digital to analog conversion module , The semaphore can be converted into a digital quantity , Output to MCU , The final display is LCD1602 On the LCD

         Smoke sensor is MQ-2 It is a kind of gas sensor . It can be used in gas detection in homes or factories . By reading the relevant chip information, we know that many kinds of gases can be detected . such as ： liquid gas 、 alcohol 、 hydrogen 、 Smoke and other gases . Its own advantages are fast response 、 Long service life 、 Good stability 、 Simple circuit design and other characteristics . Smoke sensor is a semiconductor material of tin oxide . When the temperature is 200 To 300 When the degree of , Tin dioxide will absorb oxygen in the air , Increase the resistance . When smoke is detected, it will cause the conductivity of the surface to change , In this way, the value of smoke can be detected . If the output resistance value is lower , It means that the value of the output analog signal is larger .

【 reference 】

[1] Li weiti , Guo Qiang ．《 LCD application technology 》 Beijing ： Electronic industry press ,2000 year ．

[2] Beijing Jingdian PENGYUAN Display Technology Co., Ltd ． Inside KS0108B/HD61202 Controller graphic LCD module user manual ．

[3] Zhao Maotai .《 Principle and application of intelligent instrument 》  Beijing ： Electronic industry press ,2001.

[4] Zhao Xinmin .《 Principle and design of intelligent instrument 》  Harbin Institute of Technology Press ,1995.

[5] Xu Aijun , Peng Aihua .《 SCM high level language CSTM32 Application design 》〔M〕. Beijing Industry Press ,1999.

[6] YanWeiMin Wei-min wu .《 data structure 》 tsinghua university press ,1996

[7] Ma Zhongmei et al .《 Single chip microcomputer C Language application design 》 Beijing : Beijing University of Aeronautics and Astronautics Press ,1997

[8]  Li Gang Lin Ling Wang Yan Huang, New concept SCM tutorial . Tianjin University Press ,2004 year

[9]  Hua Chengying . Tong Shibai . 《 Fundamentals of Analog Electronic Technology Third Edition 》 Beijing : Higher Education Press , 2004.4.

[10]  Ding Yuanjie . 《 Principle and application of single chip microcomputer 》. Beijing : Mechanical industry press ,1993

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