MCU + DHT11 temperature and humidity detection program

Based on the DHT11 temperature and humidity alarm system LCD1602 display operation instructions

This design system is a DHT11 temperature and humidity alarm system LCD1602 display, which can set the high temperature alarm value and low temperature alarm value of temperature, the high humidity alarm value and low temperature alarm value of humidity. When there is an alarm, the buzzer will emit a dripping alarm sound, and the green light-emitting diode will flash at the same time. The alarm information can also be seen very intuitively on the LCD1602 liquid crystal. It also has a power-off save function. The data is saved in the EEPOM inside the microcontroller. After entering the setting interface, if no key is pressed, the system will automatically exit the setting interface after 30 seconds. The humanized key setting, the key also has the function of continuous addition and subtraction. When the key is pressed, there is a key sound, that is, the buzzer calls. The key sound can be set in the menu, and the key sound can be set to turn on or off. The system also has a function to cancel the alarm return difference value to increase the anti-interference of the system.

Alarm mode: sound and light alarm    
buzzer drips alarm sound, light-emitting diode flashes.
DHT11 temperature and humidity detection

microcontroller circuit schematic diagram:

Buzzer Buzzer B1
10uF capacitor C1
20pF capacitor C2, C3
D indicator D1, D2, D3, D4,
LCD1602 LCD1
9012 transistor Q1
10K resistor R3, R4
2K resistor R1
2K resistor R2, R5
SW-PB button S1, S2, S3, S4, S5
sw-gray power switch SW1
U1 MCU U1
DHT11 temperature and humidity sensor U2
12M crystal oscillator Y1

MCU source program is as follows:

#include //Call the MCU header file

#define uchar unsigned char //unsigned character macro definition variable range 0~255

#define uint unsigned int //Unsigned integer macro definition variable range 0~65535

sbit beep = P1^4; //Buzzer

int flag_300ms;

// Definition of IO variables for buttons

uchar key_can; //Key value variable

sbit wh_led = P2^2; // Temperature alarm indicator IO port definition

sbit wl_led = P2^3; // Temperature alarm indicator IO port definition

sbit sh_led = P2^1; //Humidity alarm indicator IO port definition

sbit sl_led = P2^0; //Humidity alarm indicator IO port definition

uchar flag_en = 1;

uchar menu_1; //Menu design variables

uint t_high = 35, t_low = 10; //temperature alarm parameters

uint s_high = 80,s_low = 10; //Humidity alarm parameters

/*******************************************************************

* Name: delay_1ms()

* Function: Delay 1ms function

* Input: q

* Output: None

********************************************************************/

void delay_1ms(uint q)

{

        uint i,j;

        for(i=0;i                for(j=0;j<120;j++);

}

sbit dht11=P1^5; //Temperature sensor IO port definition

uchar table_dht11[5]={1,2,3,4,5};

uchar code table_num[]="0123456789abcdefg";

sbit rs=P1^0; //Register selection signal H: data register L: instruction register

sbit rw=P1^1; //Register selection signal H: data register L: instruction register

sbit e =P1^2; //Chip select signal falling edge trigger

/********************************************************************

* Name: delay_uint()

* Function: small delay.

* Input: None

* Output: None

***************************************************************************/

void delay_uint(uint q)

{

        while(q--);

}

/********************************************************************

* Name: write_com(uchar com)

* Function: 1602 command function

* Input: Input command value

* Output: None

***************************************************************************/

void write_com(uchar com)

{

        e=0;

        rs=0;

        rw=0;

        P0=com;

        delay_uint(25);

        e=1;

        delay_uint(100);

        e=0;

}

/********************************************************************

* Name: write_data(uchar dat)

* Function: 1602 write data function

* Input: Data to be written to 1602

* Output: None

***************************************************************************/

void write_data(uchar dat)

{

        e=0;

        rs=1;

        rw=0;

        P0=dat;

        delay_uint(25);

        e=1;

        delay_uint(100);

        e=0;        

}

/***********************LCD1602 displays specific characters****0XDF************************/

void write_zifu(uchar hang,uchar add,uchar date)

{

        if(hang==1)   

                write_com(0x80+add);

        else

                write_com(0x80+0x40+add);

        write_data(date);        

}

/***********************LCD1602 displays two decimal numbers************************/

void write_sfm2(uchar hang,uchar add,uint date)

{

        if(hang==1)   

                write_com(0x80+add);

        else

                write_com(0x80+0x40+add);

        write_data(0x30+date/10%10);

        write_data(0x30+date%10);        

}

/**************************LCD1602 displays this character function****************************/

void write_string(uchar hang,uchar add,uchar *p)

{

        if(hang==1)   

                write_com(0x80+add);

        else

                write_com(0x80+0x40+add);

                while(1)                                                                                                                 

                {

                        if(*p == '') break;

                        write_data(*p);

                        p++;

                }        

}

/***********************lcd1602 initialization settings****************************/

void init_1602() //lcd1602 initialization

{

        write_com(0x38);        

        write_com(0x0c);

        write_com(0x06);

        delay_uint(1000);

        write_string(1,0,"Wd:00 H00 L00 ");        

        write_string(2,0,"Sd:00% H00% L00% ");        

        write_zifu(1,5,0xdf); //display degree                

        write_zifu(1,10,0xdf); //display degree        

        write_zifu(1,15,0xdf); //display degree        

        write_sfm2(1,3,table_dht11[2]); //Display temperature

        write_sfm2(2,3,table_dht11[0]); //Display humidity        

        write_sfm2(1,7,t_high); //Display temperature

        write_sfm2(2,7,s_high); //Display humidity                

        write_sfm2(1,10,t_low); //Display temperature

        write_sfm2(2,10,s_low); //Display humidity                

}

/************************Independent key program*****************/

uchar key_can; //key value

void key() //Independent key program

{

        static uchar key_new;

        key_can = 20; //key value restoration

        P3 |= 0xf0;

        if((P3 & 0xf0) != 0xf0) //button pressed

        {

                delay_1ms(1); //key debounce

                if(((P3 & 0xf0) != 0xf0) && (key_new == 1))

                { //Confirm that the button was pressed

                        key_new = 0;

                        switch(P3 & 0xf0)

                        {

                                case 0xd0: key_can = 1; break; //Get the k1 key value

                                case 0xb0: key_can = 2; break; //Get the K2 key value

                                case 0x70: key_can = 3; break; //Get the k3 key value

                        }

                }                        

        }

        else 

                key_new = 1;        

}

/********************Button display function***************/

void key_with()

{

        if(key_can == 1) //Set key

        {

                menu_1++;

                if(menu_1 > 2)

                {

                        menu_1 = 0;

                        init_1602(); //lcd1602 initialization                        

                }

        }

        if(menu_1 == 1) //Set high temperature alarm

        {

                if(key_can == 2)

                {

                        t_high ++; //Set the high temperature value plus 1         

                        if(t_high > 99)

                                t_high = 99;

                }

                if(key_can == 3)

                {

                        t_high -- ; //Set the high temperature value minus 1         

                        if(t_high <= t_low)

                                t_high = t_low + 1;

                }

                write_sfm2(1,8,t_high); //Display temperature

                write_com(0x80+8); //Move the cursor to the second position

                write_com(0x0f); //Display the cursor and blink        

        }        

        if(menu_1 == 2) //Set low temperature alarm

        {

                if(key_can == 2)

                {

                        t_low ++; //Set the low temperature value plus 1 

                        if(t_low >= t_high)

                                t_low = t_high - 1;

                }

                if(key_can == 3) //Set the high temperature value minus 1 

                {

                        t_low -- ;                        

                        if(t_low <= 1)

                                t_low = 1;

                }

                write_sfm2(1,13,t_low); //Display humidity        

                write_com(0x80+13); //Move the cursor to the second position

                write_com(0x0f); //Display the cursor and blink        

        }

        if(menu_1 == 3) //Set high humidity alarm

        {

                if(key_can == 2)

                {

                        s_high ++ ; //Set the high humidity value plus 1         

                        if(s_high > 99)

                                s_high = 99;

                }

                if(key_can == 3)

                {

                        s_high -- ; //Set the high humidity value minus 1         

                        if(s_high <= s_low)

                                s_high = s_low + 1;

                }

                write_sfm2(2,8,s_high); //Display humidity

                write_com(0x80+0x40+8); //Move the cursor to the second position

                write_com(0x0f); //Display the cursor and blink        

        }        

        if(menu_1 == 4) //Set low humidity alarm

        {

                if(key_can == 2)

                {

                        s_low ++; //Set the low humidity value plus 1