Published September 16, 2020 © GPL3+

Arduino-Based Determination of an Air Humidifier Efficiency

Using Arduino and the sensors I analysed how a small air humidifier can change the parameters of the room and influence health state.

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Arduino-Based Determination of an Air Humidifier Efficiency

Things used in this project

Hardware components

Arduino UNO

Seeed Studio Grove shield for Arduino Uno

DHT11 Temperature & Humidity Sensor (4 pins)

Seeed Studio Grove - Temperature, Humidity, Pressure and Gas Sensor (BME680)

Adafruit Waterproof DS18B20 Digital temperature sensor

Software apps and online services

Vittascience

Story

Portable humidifiers are very popular for use in a variety of environments and the manufacturers of these devices promise not only humidification but also purification of the air when using their products.

I decided to check how effective the use of a humidifier is on the example of a small closed room (my office) - the size of the room is 10м².

Part 1 - Humidifier. As for the device, my choice fell on a small air humidifier with the following parameters:

dimensions: 110 x 110 x 115 mm
volume: 300ml
capacity: 35ml / h

That's how it looks in a working state (water was used as liquid everytime):

As the device was standing on my desk, I felt that the air is changed and seems to be more fresh, but I didn't know for sure what is the effect and whether the humidity increases only in the area close to the device or it is increased in whole room.

Part 2 - Arduino connection. To check the efficiency of air humidifier I used arduino board Uno, grove shield for the board and three sensors:

DHT11 temperature & humidity - to get the data about room temperature and humidity
SGP30 gas sensor - to check the CO2 concentration on the room
DS18B20 temperature sensor - to analyse the body temperature

That's how connected board with the shield and the sensors look like:

And this is the photo of the full setting with working humidifier and the electronic part:

I wrote a code to analyse the parameters and to connect the sensors with the board. I used online Vittascience coding platform to write the code, get the data graphics and save the data. My code is available online with this link or use the code below the text.

Part 3 - Experiment. I provided the analysis of room conditions and body temperature during three different periods: before usage of the humidifier, after one hour of the turned on air humidifier and after three hours of the device's work. So I made three data collections during three periods to get precise information - 9 experiments in total.

The conditions of the experiment were maintained the same:

3 meters between the working humidifier and the board with sensors
duration of the data collection was during 30min
the door of the 10м² room, where experiment was provided, was closed during all the time of the experiment

Here is how collected data looked like - this is the data that I got during the experiment that was provided one hour after the humidifier's work:

I analysed 9 excel files and got the following results:

Average parameters before the humidifier's usage were: room temperature - 25 C°, humidity level - 51%, CO2 level - 400ppm, body temperature - 37C°.
Average parameters after one hour of the humidifier's usage were: room temperature - 25 C°, humidity level - 58%, CO2 level - 400ppm, body temperature - 36.8C°.
Average parameters after three hours of the humidifier's usage were: room temperature - 24 C°, humidity level - 71%, CO2 level - 400ppm, body temperature - 36.6C°.
Common results: after one hour the humidity level increased by 13% and after three hours it reached 139% of the the base value; both room and body temperature showed a slight decrease; CO2 level didn't seem to change.

The experiment showed that even an air humidifier with small capacity can increase the humidity level in the room by 40% after three hours of work, which can positively affect both room and body temperature. But it completely doesn't not affect CO2 level.

Code

Code for arduino board

#include <Wire.h>
#include <DHT.h>
#include <Adafruit_SGP30.h>
#include <OneWire.h>

DHT dht_8(8, DHT11);
Adafruit_SGP30 sgp30;
enum DS18B20_RCODES {
  READ_OK,
  NO_SENSOR_FOUND,
  INVALID_ADDRESS,
  INVALID_SENSOR
};
OneWire ds18b20_4(4);

void serial_setupConnection(int baudrate) {
  Serial.begin(baudrate);
  while (!Serial) {
    Serial.println("En attente de l'ouverture du port série...");
    delay(1000);
  }
  Serial.println("Port série activé. Baudrate: " + String(baudrate));
}

uint16_t sgp30_readCO2() {
  if (!sgp30.IAQmeasure()) {
    Serial.println("Measurement failed");
    return 0;
  }
  else return sgp30.eCO2;
}

byte ds18b20_measure(OneWire ds, float *temperature, byte reset_search) {
  byte data[9], addr[8];
  if (reset_search) ds.reset_search();
  if (!ds.search(addr)) return NO_SENSOR_FOUND;
  if (OneWire::crc8(addr, 7) != addr[7]) return INVALID_ADDRESS;
  if (addr[0] != 0x28) return INVALID_SENSOR;
  ds.reset();
  ds.select(addr);
  ds.write(0x44, 1);
  delay(800);
  ds.reset();
  ds.select(addr);
  ds.write(0xBE);
  for (byte i=0; i<9; i++) data[i] = ds.read();
  *temperature = (int16_t) ((data[1] << 8) | data[0]) * 0.0625;
  return READ_OK;
}

float ds18b20_readTemperature(OneWire ds) {
  float temp;
  if (ds18b20_measure(ds, &temp, true) != READ_OK) {
    Serial.println(F("Erreur de lecture du capteur."));
    return;
  }
  return temp;
}


void setup() {
  serial_setupConnection(9600);
  dht_8.begin();
  while (!sgp30.begin()) {
    Serial.println("En attente du capteur SGP30...");
    delay(1000);
  }
}

void loop() {
  Serial.print("@Graph:");
  Serial.print("Room temperature:");
  Serial.print(dht_8.readTemperature());
  Serial.print("|");
  Serial.print("Room humidity:");
  Serial.print(dht_8.readHumidity());
  Serial.print("|");
  Serial.print("Room CO2:");
  Serial.print(sgp30_readCO2());
  Serial.print("|");
  Serial.print("Body temperature:");
  Serial.print(ds18b20_readTemperature(ds18b20_4));
  Serial.print("|");
  Serial.print("\n");
  delay(50);
  delay(1000*30);
}