Making a fridge like program.

Projects Programming
1

Hello users.

I am currently making a "Fridge" like program, where I need the arduino board to start cooling when it's over 25 Degrees celcius, and stop cooling when it's below 23 degrees celcius.

This is using the DHT Library

This what I've so far.

// Example testing sketch for various DHT humidity/temperature sensors
// Written by ladyada, public domain

#include "DHT.h"

#define DHTPIN 2     // what pin we're connected to

// Uncomment whatever type you're using!
//#define DHTTYPE DHT11   // DHT 11 
#define DHTTYPE DHT22   // DHT 22  (AM2302)
//#define DHTTYPE DHT21   // DHT 21 (AM2301)

// Connect pin 1 (on the left) of the sensor to +5V
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor

DHT dht(DHTPIN, DHTTYPE);

int cooler = 12;


void setup() {
  Serial.begin(9600); 
  Serial.println("DHTxx test!");
  pinMode(cooler, OUTPUT);
 
  dht.begin();
}

void loop() {
  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  float h = dht.readHumidity();
  float t = dht.readTemperature();

  // check if returns are valid, if they are NaN (not a number) then something went wrong!
  if (isnan(t) || isnan(h)) {
    Serial.println("Failed to read from DHT");
  } else {
    Serial.print("Humidity: "); 
    Serial.print(h);
    Serial.print(" %\t");
    Serial.print("Temperature: "); 
    Serial.print(t);
    Serial.println(" *C");
    
    if (t <= 24) {
      digitalWrite(cooler, LOW);
      Serial.print ("Stopped Cooling");
  }
    
    
    
   else (t >= 25) 
  {
   digitalWrite(cooler, HIGH);
    Serial.print(" Start Cooling");
  }
  }
}

This won't say anything inbetween the 24-25 period, so it's doesn't cooldown, how could I fix this?

2

Remove the else statement and replace it with another if statement.

3 
if (t >= 25) 
  {
   digitalWrite(cooler, HIGH);
    Serial.print(" Start Cooling");

Like this? This is what I tried before, but it stopped after it got below 25, wouldn't keep going until it reached the other temperature.

4

But what is stopped? Serial output? What should happen in 24 - 25 range ( When temperature is 24.5) ? You can add third if statement or else statement like this :

if ( t > 24 && t < 25) 
{
Serial.print("Temperature OK") ;
}