Arduino Projects

Wireless Temperature monitoring system using Bluetooth

Wireless temperature Monitoring Project Description:

Wireless temperature

Wireless Temperature Monitoring- This tutorial is based on the wireless Temperature monitoring using Bluetooth module, Arduino Uno and Android cell phone application. In this project, the temperature request can be sent to the Arduino at any time. This project also has a feedback system. The command is sent wirelessly to the Arduino Uno, the Arduino once receive the command then replay back with the temperature and humidity values. In this project, the famous DHT11 temperature and humidity module are used for monitoring the temperature and humidity.

This project mainly focuses on how to request the Sensors data from the Arduino, this method is best as it never keeps the Arduino busy in sending the messages again and again. So whenever you need to check the temperature and humidity values, you simply send a request command to the Arduino Uno.

For the complete step by step explanation, you can watch a video Tutorial given at the end of this article.

Amazon Links:

12v Adaptor:

Arduino Uno

Arduino Nano

Mega 2560:

DHT11 Temperature and Humidity Module:

Bluetooth Module: Hc-05:

Other Tools and Components:

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Super Starter kit for Beginners

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Digital Multimeter

Soldering iron kits

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DHT11 Temperature and Humidity sensor:

Wireless temperature

The DHT11 Temperature and Humidity Module is one of the most commonly used sensors. The DHT11 sensor most frequently is used in Weather Station projects. The DHT11 Temperature and Humidity Sensor has a total of 4 pins. Out of these 4 pins, we will use only three pins. Pin number 3 will not be used.

Wireless Temperature monitoring Circuit Diagram:

Wireless temperature

The data pin of the DHT11 sensor is connected with the Arduino’s digital pin 12. While the power supply pins are connected with the Arduino’s 5V and GND pins.

The Bluetooth module HC-05 or HC-06 is connected with the Arduino’s pins 7 and 8. The RX pin of the Bluetooth module is connected with the Arduino’s pin number 8. The TX pin of the Bluetooth module is connected with Pin 7 of the Arduino Board, while the Power supply pins are connected with the Arduino’s power supply.


Android cell phone Apk file: BlueserialApp

Wireless Temperature Monitoring Arduino Programming:

Before, you start the programming, first of all, make sure you download the DHT library. In this project, instead of using the Arduino’s default Serial Port, I will be defining another Serial Port using the SoftwareSerial library. This way I can use the Arduino’s default Serial Port only for debugging purposes.

  v = feedback request

#include <SoftwareSerial.h> 
#include "DHT.h"

#define DHTPIN 12     // what pin we're connected to

//Uncomment whatever the type of sensor we are 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
// NOTE: If using a board with 3.3V logic like an Arduino Due connect pin 1
// to 3.3V instead of 5V!
// Connect pin 2 of the sensor to whatever your DHTPIN is 
// pin3 of the sensor is not connected
// 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

// Initialize DHT sensor for normal 16mhz Arduino

char inchar; // Will hold the incoming character from the GSM shield

SoftwareSerial blue(7, 8); // bluetooth module will be connected here.

String TextForSms ;
String humidity = " Humidity: %";
String temperature = "   Temperature";
String sign = " *C";

int powerb = 6; // to power up the dht11 sensor, dht11 5v wire is connected with pin6 of the arduino. 

void setup() {

  blue.begin(9600); // original 19200
    pinMode(powerb, OUTPUT); 
  digitalWrite(powerb, HIGH); 


void loop() {

if(blue.available() == 0);

  if(blue.available() >0)
    if (inchar=='v')
  // Wait a few seconds between measurements.

  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  int h = dht.readHumidity();
  // Read temperature as Celsius
  int t = dht.readTemperature();
  // Read temperature as Fahrenheit
  int 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!");

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

//  Serial.print("Humidity: "); 
//  Serial.print(h);
//  Serial.print(" %\t");
//  Serial.print("Temperature: "); 
//  Serial.print(t);
//  Serial.print(" *C ");
  TextForSms = TextForSms + "HUMIDITY: ";
  TextForSms = TextForSms + "%    TEMPERATURE: ";
  TextForSms = TextForSms + "*C";
  TextForSms = " ";


Watch Video Tutorial:

Engr Fahad

My name is Shahzada Fahad and I am an Electrical Engineer. I have been doing Job in UAE as a site engineer in an Electrical Construction Company. Currently, I am running my own YouTube channel "Electronic Clinic", and managing this Website. My Hobbies are * Watching Movies * Music * Martial Arts * Photography * Travelling * Make Sketches and so on...


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