Arduino-Basic-Tutorial

Hardware Required

• Arduino Uno/Mega/Nano https://circuits.my/index.php/product/arduino-uno-r3/

• DHT11 https://circuits.my/index.php/product/humidity-sensor/

• Jumper https://circuits.my/index.php/product/male-to-male-cable-40pcs-20cm/ https://circuits.my/index.php/product/male-to-female-cable-40pcs-20cm/

Optional Hardware

• Breadboard https://circuits.my/index.php/product/breadboard-medium/

Hardware Connection

• DHT11 [-ve] ----> Arduino [GND]
• DHT11 [+ve] ----> Arduino [5V]
• DHT11 [S] ----> Arduino [8]

Install Required Library

• <Adafruit_Sensor.h> https://github.com/adafruit/Adafruit_Sensor

• <DHT.h>

• <DHT_U.h> https://github.com/adafruit/DHT-sensor-library

Code Explain

#include <Adafruit_Sensor.h>
#include <DHT.h>
#include <DHT_U.h>

#include is used to include outside libraries in your sketch. https://www.arduino.cc/reference/en/language/structure/further-syntax/include/

You can download and explore these library from this link:

https://github.com/adafruit/Adafruit_Sensor https://github.com/adafruit/DHT-sensor-library

This outside library is created by Adafruit for most of Adafruit sensor and DHT sensor.

#define DHTPIN 8   
#define DHTTYPE    DHT11
DHT_Unified   dht(DHTPIN, DHTTYPE);

#define DHTPIN 8 means that we define which Input Pin from Arduino is connected to the Signal Pin of DHT sensor. #define DHTTYPE DHT11 means that we define which type of DHT sensor that we used. In our case, it is DHT11 instead of DHT21 and DHT22.

DHT_Unified dht(DHTPIN, DHTTYPE); means that refer to DHT_Unified Class from the <DHT_U.h> library, a public function which refer to DHT_Unified(uint8_t pin, uint8_t type, uint8_t count=6, int32_t tempSensorId=-1, int32_t humiditySensorId=-1); is called and define as dht(DHTPIN, DHTTYPE).

DHT_Unified() ----> dht()

void setup() {
  Serial.begin(115200);
  dht.begin();
  sensor_t sensor;
  dht.temperature().getSensor(&sensor);
  dht.humidity().getSensor(&sensor);
}

void setup() is a basic Arduino IDE sketch structure. This loop will run once at the beginning of the application. https://www.arduino.cc/reference/en/language/structure/sketch/setup/

The setup() function is called when a sketch starts. Use it to initialize variables, pin modes, start using libraries, etc. The setup() function will only run once, after each powerup or reset of the Arduino board.

In this case, we are execute some function which is dht.begin(); means to execute dht() function which is sets the DHTPIN and DHTTYPE.

For deeper understanding, you can study this code which is from <DHT_U.h> library. https://github.com/adafruit/Adafruit_DHT_Unified/blob/master/DHT_U.h

Serial.begin(115200); means we sets the data rate in bits per second (baud) for serial data transmission. For communicating with Serial Monitor, make sure to use one of the baud rates listed in the menu at the bottom right corner of its screen.

For deeper understanding, you can study this code https://www.arduino.cc/reference/tr/language/functions/communication/serial/begin/

dht.temperature().getSensor(&sensor);
dht.humidity().getSensor(&sensor);

These function refers to <DHT_U.cpp> which set up the sensor based on the value DHTPIN and DHTTYPE that been defined by us.

If you want to know exactly what happen in the library, you can always refer to the code in the link below.

https://github.com/adafruit/Adafruit_DHT_Unified/blob/master/DHT_U.cpp

The loop() function does precisely what its name suggests, and loops consecutively, allowing your program to change and respond. Use it to actively control the Arduino board.

  sensors_event_t event;  
  dht.temperature().getEvent(&event); 
  if (isnan(event.temperature)) {
    Serial.println("Error reading temperature!");
  }
  else {
    Serial.print("Temperature: ");
    Serial.print(event.temperature);
    Serial.println(" *C");
  }

This code is to get temperature event and print its value.

dht.temperature().getEvent(&event); // get temperature event Serial.print(event.temperature); //print temperature value

    dht.humidity().getEvent(&event);
    
    if (isnan(event.relative_humidity)) {
      Serial.println(F("Error reading humidity!"));
    }
    else {
      Serial.print(F("Humidity: "));
      Serial.print(event.relative_humidity);
      Serial.println(F("%"));
    }

This code is to get humidity event and print its value.

dht.humidity().getEvent(&event); // get humidity event Serial.print(event.relative_humidity); //print humidity value

delay(1500); // Lastly, we have to put delay at least 1.5 sec because DHT11 has 1 Hz sampling rate (once every second). *at least 1 sec delay must be put before it read DHT11 again.

Thats it.

Please comment this explanation so I can improve.