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I have this code that takes temperature and humidity values from a DHT11 sensor and number of faces from an external python code and prints them on an OLED screen but instead of values of variables it keeps printing 0, how can I solve it? (Sorry some parts are not in English but just consider them as random variable names.)

//dht11 kodu için ayarlamalar
#include <dht.h>
dht DHT;
#define DHT11_PIN 7

//ekran için ayarlamalar
#include "U8glib.h"
U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_DEV_0);
char bufferX [20];
char bufferY [20];
char bufferZ [20];

//fan kodu için ayarlamalar
int mot1 = 8;
int mot2 = 9;
int en1 = 10;
int dir = 6;
bool state = true;
int nob = A0;
int val = 0;
int fan_hizi = 0;
String faces_str;
int faces;
float sicaklik;
float nem;

void draw(void)
{
  u8g.setFont(u8g_font_unifont);
  u8g.drawStr( 0, 15, bufferX);
  u8g.drawStr( 0, 30, bufferX);
  u8g.drawStr( 0, 45, bufferY);
  u8g.drawStr( 0, 60, bufferZ);
}

void setup() {
  Serial.begin(9600); //iletişim ve dht11 verisi
   
  // pin ayarları
  pinMode(mot1,OUTPUT);
  pinMode(mot2,OUTPUT);
  pinMode(en1,OUTPUT);
  pinMode(dir,INPUT_PULLUP);
}


void loop() {
  //dht11 kodu
  sicaklik = DHT.temperature;
  nem = DHT.humidity;
  delay(1000);


  //iletişim kodu
  if(Serial.available() > 0) {
    faces_str = Serial.readString();
    faces = faces_str.toInt();
  }

  Serial.print(faces);
  
  //sınırlar
  if(faces == 0 && sicaklik < 25 && nem < 65) {
    fan_hizi = 50;
    digitalWrite(13, HIGH);
    digitalWrite(12, LOW);
  }
  if(faces >= 1 || sicaklik >= 25 || nem >= 65) {
    fan_hizi = 250;
    digitalWrite(13, LOW);
    digitalWrite(12, HIGH);
  }

  //ekran
  sprintf(bufferX, "Yuzler: %d", faces);
  sprintf(bufferY, "Sicaklik: %d", sicaklik);
  sprintf(bufferZ, "Nem: %d", nem);
   u8g.firstPage();
  do {
  draw();
    } 
  while ( u8g.nextPage() );
  delay(10);

  //fan kodu
  analogWrite(en1, fan_hizi);
  digitalWrite(mot1, HIGH);
  digitalWrite(mot2, LOW);
  delay(1000);
  digitalWrite(mot1, LOW);
  }
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  • maybe it is printing a 0 because it is receiving a 0 ... do some debugging
    – jsotola
    Jan 30 at 7:06
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I do not understand, how you initialize the DHT sensor object. (I wonder why this compiles at all.)

Your way:

//dht11 kodu için ayarlamalar
#include <dht.h>
dht DHT;
#define DHT11_PIN 7

I would use:

//dht11 kodu için ayarlamalar
#include <DHT.h>
#define DHT11_PIN 7

DHT dht( DHT11_PIN, DHT11 );

Don't forget to start the DHT object with:

void setup() {
  // ... code removed for brevity
  dht.begin();
}

Now use the dht object instad of the DHT class.

sicaklik = dht.readTemperature();
nem = dht.readHumidity();

You did not specify what libraries you have used. But I tried all DHT libs I could find and none of them compiled with your code without errors.

The following code compiles on my IDE for an arduino UNO having olivers ug8lib and adafruits DHT sensor library installed. BTW: You even did not mention the Arduino/ESP you used. So I guess it is an UNO.

//dht11 kodu için ayarlamalar
#include "DHT.h"
#define DHT11_PIN 7
DHT dht( DHT11_PIN, DHT11 );

//ekran için ayarlamalar
#include "U8glib.h"
U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_DEV_0);
char bufferX [20];
char bufferY [20];
char bufferZ [20];

//fan kodu için ayarlamalar
int mot1 = 8;
int m ot2 = 9;
int en1 = 10;
int dir = 6;
bool state = true;
int nob = A0;
int val = 0;
int fan_hizi = 0;
String faces_str;
int faces;
float sicaklik;
float nem;

void draw(void)
{
  u8g.setFont(u8g_font_unifont);
  u8g.drawStr( 0, 15, bufferX);
  u8g.drawStr( 0, 30, bufferX);
  u8g.drawStr( 0, 45, bufferY);
  u8g.drawStr( 0, 60, bufferZ);
}

void setup() 
{
  Serial.begin(9600); //iletişim ve dht11 verisi
   
  // pin ayarları
  pinMode(mot1,OUTPUT);
  pinMode(mot2,OUTPUT);
  pinMode(en1,OUTPUT);
  pinMode(dir,INPUT_PULLUP);
}


void loop() 
{
  //dht11 kodu
  sicaklik = dht.readTemperature();
  nem = dht.readHumidity();
  delay(1000);

  //iletişim kodu
  if(Serial.available() > 0) 
  {
    faces_str = Serial.readString();
    faces = faces_str.toInt();
  }

  Serial.print(faces);
  
  //sınırlar
  if(faces == 0 && sicaklik < 25 && nem < 65) 
  {
    fan_hizi = 50;
    digitalWrite(13, HIGH);
    digitalWrite(12, LOW);
  }
  
  if(faces >= 1 || sicaklik >= 25 || nem >= 65) 
  {
    fan_hizi = 250;
    digitalWrite(13, LOW);
    digitalWrite(12, HIGH);
  }

  //ekran
  sprintf(bufferX, "Yuzler: %d", faces);
  sprintf(bufferY, "Sicaklik: %d", sicaklik);
  sprintf(bufferZ, "Nem: %d", nem);
  u8g.firstPage();
 
  do 
  {
    draw();
  }  while ( u8g.nextPage() );
  
  delay(10);
 
  //fan kodu
  analogWrite(en1, fan_hizi);
  digitalWrite(mot1, HIGH);
  digitalWrite(mot2, LOW);
  delay(1000);
  digitalWrite(mot1, LOW);
}

I do not have the time to assemble the hardware to try it. So I can say it compiles, but I can not say it works.

EDIT:

Now I found adidax "DHT11 lib". your code compiles with this library. But you forgott to read the values from the sensor, before you read them from the variables.

The following line is missing:

void loop() {
  //dht11 kodu
  DHT.read( DHT11_PIN ); // <-- this line is missing
  sicaklik = DHT.temperature;
  nem = DHT.humidity;
...
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  • thank you for your answer. i'm pretty new in arduino. yes, i used a uno board. and about dht11, i used a code i found online. i don't know how exactly it works.
    – vueenx
    Jan 30 at 23:20

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