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DHT11 Relative Humidity and Temperature Sensor

 
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sshahryiar



Joined: 05 May 2010
Posts: 94
Location: Dhaka, Bangladesh

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DHT11 Relative Humidity and Temperature Sensor
PostPosted: Fri Jan 17, 2014 8:28 am     Reply with quote
DHT11.h
Code:

#define DHT11_pin PIN_A0

unsigned char values[5];

void DHT11_init();
unsigned char get_byte();
unsigned char get_data();


DHT11.c
Code:

#include "DHT11.h"

void DHT11_init()
{
   output_float(DHT11_pin);
   delay_ms(1000);
}

unsigned char get_byte()
{
   unsigned char s = 0;
   unsigned char value = 0;

   for(s = 0; s < 8; s += 1)
   {
      value <<= 1;
      while(!input(DHT11_pin));
      delay_us(30);

      if(input(DHT11_pin))
      {
          value |= 1;
      }
      while(input(DHT11_pin));
   }
   return value;
}


unsigned char get_data()
{
   short chk = 0;
   unsigned char s = 0;
   unsigned char check_sum = 0;

   output_high(DHT11_pin);
   output_low(DHT11_pin);
   delay_ms(18);
   output_high(DHT11_pin);
   delay_us(26);
   
   chk = input(DHT11_pin);
   if(chk)
   {
      return 1;
   }
   delay_us(80);
   
   chk = input(DHT11_pin);
   if(!chk)
   {
      return 2;
   }
   delay_us(80);

   for(s = 0; s <= 4; s += 1)
   {
       values[s] = get_byte();
   }
 
   output_high(DHT11_pin);
   
   for(s = 0; s < 4; s += 1)
   {
       check_sum += values[s];
   }
   
   if(check_sum != values[4])
   {
      return 3;
   }
   else
   {
      return 0;
   }
}


Example:

Code:

#include <16F84A.h>
#device *= 16
#fuses NOWDT, PUT, PROTECT, XT
#use delay (clock = 4MHz)

#include <lcd420.c>
#include "DHT11.c"

const unsigned char symbols[8]=
{       
    0x07, 0x05, 0x05, 0x07, 0x00, 0x00, 0x00, 0x00
};

void setup();
void lcd_symbols();

void main()
{
   unsigned char state = 0;
   setup();
   
   while(TRUE)
   {
      state = get_data();
     
      switch(state)
      {
            case 1:
            {
            }
            case 2:
            {
               lcd_putc("\fNo Sensor Found!");
               break;
            }
            case 3:
            {
               lcd_putc("\fChecksum Error!");
               break;
            }
            default:
            {
               lcd_gotoxy(1, 1);
               lcd_putc("Tmp/ C: ");
               lcd_gotoxy(5, 1);
               lcd_putc(0);
               lcd_gotoxy(1, 2);
               lcd_putc("R.H/ %: ");
               lcd_gotoxy(9, 1);
               printf(lcd_putc, "%3u.%03u ", values[2], values[3]);
               lcd_gotoxy(9, 2);
               printf(lcd_putc, "%3u.%03u ", values[0], values[1]);
               break;
            }
      }
      delay_ms(1000);
   };
}


void setup()
{
   disable_interrupts(global);
   port_B_pullups(FALSE);
   setup_timer_0(T0_internal | T0_8_bit);
   set_timer0(0);
   DHT11_init();
   lcd_init();
   lcd_putc("\f");
   lcd_symbols();
}

void lcd_symbols() 
{
   unsigned char i = 0;             

   lcd_send_byte(0, 0x40);

   for(i = 0; i < 8; i++)
   {
        lcd_send_byte(1, symbols[i]);
   }
   lcd_send_byte(0, 0x80);
}

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SShahryiar
Leandro



Joined: 18 Feb 2014
Posts: 12
Location: Brasil

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is possible use multiples dht11?
PostPosted: Wed Mar 18, 2015 5:54 pm     Reply with quote
Hi all!

I need use 4 dht11 in one pic, is possble adapt this code for this?
sshahryiar



Joined: 05 May 2010
Posts: 94
Location: Dhaka, Bangladesh

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multiple DHT11
PostPosted: Mon Mar 23, 2015 11:07 pm     Reply with quote
You can use a MUX when you need to use multiple DHT11 sensors....
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SShahryiar
andresgallego0126



Joined: 19 Apr 2015
Posts: 1

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Re: DHT11 Relative Humidity and Temperature Sensor
PostPosted: Sun Apr 19, 2015 10:32 am     Reply with quote
Hello i can use R232 in dht11 library?
sshahryiar



Joined: 05 May 2010
Posts: 94
Location: Dhaka, Bangladesh

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RS232
PostPosted: Sun Apr 19, 2015 8:38 pm     Reply with quote
Quote:
Hello i can use R232 in dht11 library?


RS232 and DHT11 library are not dependent on each other....
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wangine



Joined: 07 Jul 2009
Posts: 98
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PostPosted: Sun Aug 23, 2015 5:30 pm     Reply with quote
Hello. Can i use DHT22 instead of DHT11 ? I can't find dht11 in my country, only dht22. Also DHT22 seems to be more accurate. I try to compare datasheets of each but on DHT22 is in chinese. I'm lost here. Thank you.
sshahryiar



Joined: 05 May 2010
Posts: 94
Location: Dhaka, Bangladesh

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DHT22 instead of DHT11
PostPosted: Sun Aug 23, 2015 8:37 pm     Reply with quote
Yeah you can but you'll need to change the values in the delay functions according to DHT22's datasheet.... Study the delays used in this library and compare them with the timings given in DHT11's datasheet.... You can then decide what will be the delays for DHT22....
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gianhenrique



Joined: 20 Dec 2010
Posts: 8

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Alarm
PostPosted: Wed Sep 30, 2015 3:28 am     Reply with quote
Hello guys,

I would like to know, if I want to make a Alarm with some temperature or humidity... How variable can I read for compare with some value, then make a decision?

Have you some examples?

Thanks
exceps



Joined: 26 Jan 2016
Posts: 1
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Re: DHT11 Relative Humidity and Temperature Sensor
PostPosted: Tue Jan 26, 2016 12:00 pm     Reply with quote
I used this library but it does not work for me. I was simulating in Proteus
and it tells me it does not find the sensor (sensor not found!) Can you
help me please !!!
sshahryiar



Joined: 05 May 2010
Posts: 94
Location: Dhaka, Bangladesh

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Proteus Sim....
PostPosted: Tue Jan 26, 2016 7:32 pm     Reply with quote
Don't depend on Proteus sim as it sometimes fail terribly.... Test it in real life.... Here's my test video:
https://www.youtube.com/watch?v=uYR1GkMOCGw

By the way where did you get the model for DHT11 in Proteus?
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SShahryiar
cvargcal



Joined: 17 Feb 2015
Posts: 134

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Re: DHT11 Relative Humidity and Temperature Sensor
PostPosted: Sun Jun 19, 2016 12:17 am     Reply with quote
sshahryiar wrote:
DHT11.h
Code:

#define DHT11_pin PIN_A0

unsigned char values[5];

void DHT11_init();
unsigned char get_byte();
unsigned char get_data();


DHT11.c
Code:

#include "DHT11.h"

void DHT11_init()
{
   output_float(DHT11_pin);
   delay_ms(1000);
}

unsigned char get_byte()
{
   unsigned char s = 0;
   unsigned char value = 0;

   for(s = 0; s < 8; s += 1)
   {
      value <<= 1;
      while(!input(DHT11_pin));
      delay_us(30);

      if(input(DHT11_pin))
      {
          value |= 1;
      }
      while(input(DHT11_pin));
   }
   return value;
}


unsigned char get_data()
{
   short chk = 0;
   unsigned char s = 0;
   unsigned char check_sum = 0;

   output_high(DHT11_pin);
   output_low(DHT11_pin);
   delay_ms(18);
   output_high(DHT11_pin);
   delay_us(26);
   
   chk = input(DHT11_pin);
   if(chk)
   {
      return 1;
   }
   delay_us(80);
   
   chk = input(DHT11_pin);
   if(!chk)
   {
      return 2;
   }
   delay_us(80);

   for(s = 0; s <= 4; s += 1)
   {
       values[s] = get_byte();
   }
 
   output_high(DHT11_pin);
   
   for(s = 0; s < 4; s += 1)
   {
       check_sum += values[s];
   }
   
   if(check_sum != values[4])
   {
      return 3;
   }
   else
   {
      return 0;
   }
}


Example:

Code:

#include <16F84A.h>
#device *= 16
#fuses NOWDT, PUT, PROTECT, XT
#use delay (clock = 4MHz)

#include <lcd420.c>
#include "DHT11.c"

const unsigned char symbols[8]=
{       
    0x07, 0x05, 0x05, 0x07, 0x00, 0x00, 0x00, 0x00
};

void setup();
void lcd_symbols();

void main()
{
   unsigned char state = 0;
   setup();
   
   while(TRUE)
   {
      state = get_data();
     
      switch(state)
      {
            case 1:
            {
            }
            case 2:
            {
               lcd_putc("\fNo Sensor Found!");
               break;
            }
            case 3:
            {
               lcd_putc("\fChecksum Error!");
               break;
            }
            default:
            {
               lcd_gotoxy(1, 1);
               lcd_putc("Tmp/ C: ");
               lcd_gotoxy(5, 1);
               lcd_putc(0);
               lcd_gotoxy(1, 2);
               lcd_putc("R.H/ %: ");
               lcd_gotoxy(9, 1);
               printf(lcd_putc, "%3u.%03u ", values[2], values[3]);
               lcd_gotoxy(9, 2);
               printf(lcd_putc, "%3u.%03u ", values[0], values[1]);
               break;
            }
      }
      delay_ms(1000);
   };
}


void setup()
{
   disable_interrupts(global);
   port_B_pullups(FALSE);
   setup_timer_0(T0_internal | T0_8_bit);
   set_timer0(0);
   DHT11_init();
   lcd_init();
   lcd_putc("\f");
   lcd_symbols();
}

void lcd_symbols() 
{
   unsigned char i = 0;             

   lcd_send_byte(0, 0x40);

   for(i = 0; i < 8; i++)
   {
        lcd_send_byte(1, symbols[i]);
   }
   lcd_send_byte(0, 0x80);
}


I try simulate this but no work.. alway stay in "no sensor found" This if work?
sshahryiar



Joined: 05 May 2010
Posts: 94
Location: Dhaka, Bangladesh

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DHT11 Simulation
PostPosted: Sun Jun 19, 2016 12:23 am     Reply with quote
It won't work in simulation....
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cvargcal



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Posts: 134

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Re: DHT11 Simulation
PostPosted: Sun Jun 19, 2016 11:47 am     Reply with quote
sshahryiar wrote:
It won't work in simulation....

I use this function:
Code:


set_tris_a(0b11111110);  // With A0

void DHT11()
{
     state = get_data();
     
     switch(state)
      {
            case 1:           
            case 2: fprintf(uart1,"No Sensor Found!"); break;
            case 3: fprintf(uart1,"Checksum Error!");  break;
       
            default:
                  fprintf(uart1,"Tmp/ C: %3u.%03u ", values[2], values[3]);
                  //fprintf(uart1,"R.H/ %: %3u.%03u ", values[0], values[1]);
                 break;       
  }
}


But no work good ... show this "Tmp/ C: 253.127" in real not simulate
LuisdelaTorre



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Posts: 1
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Re: is possible use multiples dht11?
PostPosted: Thu Aug 11, 2016 12:08 pm     Reply with quote
Leandro wrote:
Hi all!

I need use 4 dht11 in one pic, is possble adapt this code for this?
sshahryiar



Joined: 05 May 2010
Posts: 94
Location: Dhaka, Bangladesh

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Multiple DHT Sensor
PostPosted: Sat Aug 13, 2016 10:26 pm     Reply with quote
Yeah I think you can use multiple DHT sensors using a analog MUX like 4051....
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