Published September 9, 2025

Temperature Controlled Fan using Arduino

Temperature controlling is required in many places such as server rooms, houses, industries, etc. So this project aims to do such thing.

BeginnerShowcase (no instructions)3 hours45

Temperature Controlled Fan using Arduino

Things used in this project

Hardware components

Arduino UNO

USB-A to B Cable

DHT11 Temperature & Humidity Sensor (4 pins)

Axial Fan, 12 VDC

General Purpose Transistor PNP

Adafruit RGB Backlight LCD - 16x2

Jumper wires (generic)

Breadboard (generic)

Software apps and online services

Arduino IDE

Story

Have you ever wished your desk fan could sense when you're too warm and switch itself on? SmartTempFan does exactly that. Using a DHT11 sensor to monitor temperature, this compact Arduino system automatically powers a fan when things heat up—plus, it shows both temperature and fan speed on an LCD for a polished, interactive experience.

Built for bedrooms, small offices, or workstations, SmartTempFan adapts to your comfort needs without you lifting a finger. It’s a great project for demonstrating environmental sensing, automation, and display integration.

Circuit Connection

Code

Arduino Code

#include "DHT.h"
#include<LiquidCrystal.h>
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);
#define DHTPIN 12     // what pin we're connected to


#define DHTTYPE DHT11   // DHT 11 

#define pwm 9

byte degree[8] = 
              {
                0b00011,
                0b00011,
                0b00000,
                0b00000,
                0b00000,
                0b00000,
                0b00000,
                0b00000
              };
// Initialize DHT sensor for normal 16mhz Arduino
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  lcd.begin(16, 2);
 lcd.createChar(1, degree);
 lcd.clear();
 lcd.print("   Fan Speed  ");
 lcd.setCursor(0,1);
 lcd.print("  Controlling ");
 delay(2000);
 analogWrite(pwm, 255);
 lcd.clear();
 lcd.print("Robu ");
 delay(2000);
  Serial.begin(9600); 
  dht.begin();
}

void loop() {
  // Wait a few seconds between measurements.
  delay(2000);

  // 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();
  // Read temperature as Celsius
  float t = dht.readTemperature();
  // Read temperature as Fahrenheit
  float f = dht.readTemperature(true);
  
  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  // Compute heat index
  // Must send in t in Fahrenheit!
  float hi = dht.computeHeatIndex(f, h);

  Serial.print("Humidity: "); 
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("temperature: "); 
  Serial.print(t);
  Serial.print(" *C ");
  Serial.print(f);
  Serial.print(" *F\t");
  Serial.print("Heat index: ");
  Serial.print(hi);
  Serial.println(" *F");

    lcd.setCursor(0,0);
  lcd.print("temp: ");
  lcd.print(t);   // Printing terature on LCD
  lcd.print(" C");
  lcd.setCursor(0,1);
   if(t <20 )
    { 
      analogWrite(9,0);
      lcd.print("Fan OFF            ");
      delay(100);
    }
    
    else if(t==26)
    {             
      analogWrite(pwm, 51);
      lcd.print("Fan Speed: 20%   ");
      delay(100);
    }
    
     else if(t==20)
    {
      analogWrite(pwm, 102);
      lcd.print("Fan Speed: 40%   ");
      delay(100);
    }
    
     else if(t==28)
    {
      analogWrite(pwm, 153);
      lcd.print("Fan Speed: 60%   ");
      delay(100);
    }
    
    else if(t==29)
    {
      analogWrite(pwm, 204);
      
      lcd.print("Fan Speed: 80%    ");
      delay(100);
    }
     else if(t>29)
    {
      analogWrite(pwm, 255);
      lcd.print("Fan Speed: 100%   ");
      delay(100);
    } 
  delay(3000);
}