Introduction: Blynk+GSM Sim800+Arduino Uno+DHT11

About: Master in Electronics Engineering

Temperature monitoring have wide application in daily life. In modern day keeping an eye on temperature of places such as server rooms, hospital rooms, warehouses and green houses can help solve many problems. But with the use of normal temperature sensors, someone needs to go to the place in order to view the temperature. But with the development of GSM network, one can easily connect the sensor with GSM network, so that you don’t need to be present near the sensor in order to view the temperature. You can just pick up your smartphone and open blynk app to see temperature and humidity, app will also notify you by push notification and email when temperature goes above required level .

Step 1: Required Hardware:

1. Arduino Uno

2. DHT11/DHT22

3. GSM SIM800 OR SIM900A

4. Blynk App

5. Jumper Wires

6. Breadboard

Step 2: Connections:

In arduino Code we are using software serial library in which we defined pin 2 of arduino as Rx and pin 3 of Arduino as Tx.

Connections as following:

pin 2 rx => tx of gsm

pin 3 tx => rx of gsm

pin 8 => data pin of DHT11

gnd => pin 4 of DHT11

gnd => gnd pin of gsm

5v => pin 1 of DHT11

12v power supply => gsm

Step 3: Setting Up Blynk App:

Download Blynk App from Play Store link below


Open the App

New Project > Give a name to Project > Choose Device Arduino Uno > Connection Type GSM > Create

Auth Token was sent to your email id registered

> Press OK

>Click on + sign > Add Gauge x2, History Graph, Notification, Email

> Click on Gauge 1st Give name Temperature INPUT as Virtual V1, range 0 to 100

> Click on Gauge 2nd give name Humidity INPUT as Virtual v2, range 0 to 100.

> Click on History graph in 1st column give name Temperature Input as virtual v1, 2nd column give name as humidity input as virtual v2.

>Install email & Notification

Step 4: Uploading Sketch:

Add DHT11 library to your arduino IDE, link below

To add this library download zip file > open arduino ide > goto sketch > include library > add zip file

Add Blynk Library in attachment.


Copy contents of library to library folder of ARDUINO IDE & tools to tools folder.

Upload the code in attachment , do not forget to paste token from your email and APN of your service provider.

Step 5: It Works!!

Now project is completed.

Note that gsm modem will go in sleep for some time after sending values to save power, it will automaticall awake and again send values.

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