"Failed to read" message on my LCD

Projects General Guidance
1 
#include "DHT.h"           // Including DHT22 library
#include "LiquidCrystal.h" // Including LCD library

#define DHTPIN 6      // Declaring pin 6 for communicating to DHT22 sensor
#define DHTTYPE DHT22 // Declaring the type of DHT sensor we are using (DHT22 or DHT11)

DHT dht(DHTPIN, DHTTYPE);          // Declaring DHT connection and type
LiquidCrystal lcd(12,11,10,9,8,7); // Declaring LCD connections

int Motor_Pin1 = 4;  // pin 2 on L293D
int Motor_Pin2 = 3;  // pin 7 on L293D
int Enable = 5;      // pin 1 on L293D
int val;
int button = 2; //button input on arduino pin 2
int count=0;
int total=0;

void setup() {
  pinMode(Motor_Pin1, OUTPUT); 
  pinMode(Motor_Pin2, OUTPUT);
  pinMode(Enable, OUTPUT);
  pinMode(button, INPUT);
  lcd.begin(16,2); // Initializes the 16x2 LCD
  dht.begin();     // Initializes DHT sensor
}

void loop() {
  lcd.clear();                        // Clear LCD

  float temp = dht.readTemperature(); // Reading the temperature in Celsius
  float hum = dht.readHumidity (); //Reading the humidity

  if (isnan(temp)) {                  // Validating received data
    lcd.print("Failed to read");
    delay(1000);
    return;
  }
  val=digitalRead(button);
  if (val==HIGH){
    total=count++;
    delay (250);
  }
  if(total>=3){
    total=0; 
  }
 
  lcd.setCursor(0,0);

  if(total=0){{
  lcd.print(total);
  lcd.print(" T:");
  lcd.print(temp);      // Writing temperature in the first row
  lcd.print("C");
  lcd.setCursor(0,1);}
 
    if(temp <25 ) {                 // If the temperature less than 25
    analogWrite(Enable,0);        // 0% PWM duty cycle
    lcd.print("Fan OFF ");     
    delay(100);
  }
    else if(temp>=25 & temp<30) {      // If the temperature is between 25 & 30
    analogWrite(Enable, 77);         // 30% of maximum duty cycle value (255).
    lcd.print("Fan Speed: 30% ");
    delay(100);
  }
    else if(temp>=30 & temp<35) {      // If the temperature is between 30 & 35
    analogWrite(Enable, 153);        // 60% of maximum duty cycle value (255).
    lcd.print("Fan Speed: 60% ");
    delay(100);
  }
    else if(temp>=35) {                // If the temperature is above 35
    analogWrite(Enable, 255);        // 100% duty cycle
    lcd.print("Fan Speed: 100%   ");
    delay(100);
  }
  }
  else if(total=1){{
  lcd.print(total);
  lcd.print(" H:");
  lcd.print(hum);
  lcd.print("%");
  lcd.setCursor(0,1);}
 
    if(hum>=85) {                // If the temperature is above 35
    analogWrite(Enable, 255);        // 100% duty cycle
    lcd.print("Fan Speed: 100%   ");
    delay(100);
  }
    else if(hum>=80 & hum<85) {      // If the temperature is between 30 & 35
    analogWrite(Enable, 153);        // 60% of maximum duty cycle value (255).
    lcd.print("Fan Speed: 60% ");
    delay(100);
  }
    else if(hum<80) {                 // If the temperature less than 25
    analogWrite(Enable,0);        // 0% PWM duty cycle
    lcd.print("Fan OFF ");     
    delay(100);
  }
  }
 
  else if(total=2){{
  lcd.print(total);
  lcd.print("T:");
  lcd.print(temp);      // Writing temperature in the first row
  lcd.print("C");
  lcd.setCursor(0,1);
  lcd.print("H:");
  lcd.print(hum);}
 
   if((temp>=35)|(hum>=85)) {                // If the temperature is above 35
    analogWrite(Enable, 255);        // 100% duty cycle
    lcd.print(" F:100%");
    delay(100);
  }
  else if((temp>=30 & temp<35)|(hum>=80 & hum<85)) {      // If the temperature is between 30 & 35
    analogWrite(Enable, 153);        // 60% of maximum duty cycle value (255).
    lcd.print(" F:60%");
    delay(100);
  }
  else if(temp>=25 & temp<30) {      // If the temperature is between 25 & 30
    analogWrite(Enable, 77);         // 30% of maximum duty cycle value (255).
    lcd.print("F:30%");
    delay(100);
  }
  else if(temp <25 | hum <80 ) {                 // If the temperature less than 25
    analogWrite(Enable,0);        // 0% PWM duty cycle
    lcd.print("F:OFF");     
    delay(100);
  }}

  digitalWrite(Motor_Pin1, LOW);  // To drive the motor in a particular direction
  digitalWrite(Motor_Pin2, HIGH); // To drive the motor in a particular direction

  delay(2000); // 2 seconds delay
}

Every time I am keep getting "Failed to read" message on my LCD.
Where are the mistake i did in this coding or SCHEMATIC.

2

sabitkhan:
Every time I am keep getting "Failed to read" message on my LCD.

That is because your code says to print this if "temp" is something that is "Not a Number".

So you have to figure out why what you are feeding into "temp" is in fact, not a number. :grin:

Clearly you did not write this code or else you would know what it does. :astonished: Who did, and what do you want to do with it?

3

Hint: Your DHT22 is not connected. :roll_eyes:

4

The Arduino may have not the number format expected by isnan(). What's shown if you drop this test?