Published February 2, 2019 © GPL3+

Humidity Sensor-Controlled Bathroom Exhaust Fan

Accumulation of moisture in a closed up space like a bathroom can lead to the appearance of mould, which can cause health issues.

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Humidity Sensor-Controlled Bathroom Exhaust Fan

Things used in this project

Hardware components

Arduino Nano R3

DHT11 Temperature & Humidity Sensor (4 pins)

12V 200mm DIA computer casing fan

Adafruit MOSFET board

12v 1A power supply

Jumper wires (generic)

Hand tools and fabrication machines

Hot glue gun (generic)

Story

This project is designed to sense the humidity level in a bathroom and ventilate it until the wet floor dries up to minimise the build-up of humidity in the enclosed space.

Bathrooms are normally fitted with exhaust fans to remove vapour while we shower, for example, and are switched off the moment we are done. The wet floor will dry up by itself but the humidity remains in the bathroom. Over time, the build-up of moisture results in the growth of mould, which can cause severe health issues (ttps://www.betterhealth.vic.gov.au/health/conditionsandtreatments/mould-and-your-health)

Leaving the main exhaust fan ON can be an option, but is rather noisy and adds on to the electricity bill.

In this project, I make use of a DHT-11 humidity sensor, a large computer casing fan (200mm DIA, 12V 300mA), an Arduino Nano, and a MOSFET board to do the job. Eventually, I will be hooking it up to my earlier project on Solar Tracking.

Code

Arduino Sketch

#include <SimpleDHT.h>

//Declaring digital pin no 2 as the dht11 data pin

int pinDHT11 = 2;
int DHTpower = 3;
int Fan = 13;
SimpleDHT11 dht11;

void setup() {
  pinMode(Fan, OUTPUT);
  pinMode(DHTpower, OUTPUT);
  digitalWrite(DHTpower, LOW);
  digitalWrite(Fan, LOW);
  Serial.begin(9600);   
}

void loop() {
  delay(1000);
  RHcheck();                        //check Humidity Level
  delay(15000);                     //wait 15sec
  }


void RHcheck() {                    //Check Humidity Level Function
  digitalWrite(DHTpower, HIGH);     //On Humidity Sensor
  delay(5000);
  Serial.println("============ Check Humidity ===============");
  delay(1000);
  Serial.println("DHT11 readings...");
   
  byte temperature = 0;
  byte humidity = 0;
  int err = SimpleDHTErrSuccess;

  //This bit will tell our Arduino what to do if there is some sort of an error at getting readings from our sensor
  if ((err = dht11.read(pinDHT11, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
    Serial.print("No reading , err="); Serial.println(err);delay(1000);
    return;
  }
  Serial.print("Readings: ");
  Serial.print((int)temperature); Serial.print(" C, ");
  Serial.print((int)humidity); Serial.println(" %");
  delay(500);
  if((int)humidity < 50){
    digitalWrite(DHTpower, LOW);
    delay(500);
    Serial.println("Fan OFF");
    delay(500);
    digitalWrite(Fan, LOW);
  }else{
    if ((int)humidity > 58){
      Serial.println("Humidity > 58%");
      digitalWrite(DHTpower, LOW);
      delay(500);
      Serial.println("Fan ON @ full speed");
      delay(500);
      digitalWrite(Fan, HIGH);
    }else{
      Serial.println("50% < Humidity < 58%");
      digitalWrite(DHTpower, LOW);
      delay(500);
      Serial.println("Fan ON @ low speed");
      delay(500);
      analogWrite(Fan, 150);
    }
  }
 }