How to Make IOT Temperature Sensor

About: 18 year-old passionate in Electronics

If you live in a place with erratic weather, you know the pain of switching between jacket and gym clothes.Today, we will construct two sensors, placed indoor and outdoor respectively, that will send temperature readings to our phone via the internet to allow for easy monitoring.

Let's start building!

Step 1: Gather Up the Necessary Items

You'll need a couple of components and tools:


2x 18650 Battery

2x 18650 Battery Holder

2x Adafruit Huzzah Feather Breakout Board

2x DHT11 sensor

2x 10K Resistor

Pin Headers


Copper Wires


Soldering equipment

3D Printer (Or you can just send your stl files to 3D printing companies and have them ship it to you)

Step 2: Constructing the Circuit on a Breadboard

Before we solder, let's test everything to ensure that all works well before we make it permanent.

I've provided schematic above. Wire up your circuit according to the circuit. An important note here, the schematic is using a normal Adafruit Huzzah Feather board but I'm using a Adafruit Huzzah Breakout board instead. It is pretty much similar minus the on board FTDI chip. The connection between GPIO6 and Reset pin is for the deep sleep.

Source code can be found here.

Step 3: Make It Permanent

Go ahead and bust out your perfboard and solder it together. Use a perfboard that is as small form factor as possible.

If you're using my 3D .STL files, ensure that you are using a similar perfboard

Step 4: 3D Printing

If you're using a different sized perfboard, you'll have to design your own casing. But if you're using a similar or smaller perfboard, you should be able to fit everything into the casing I've designed.

So bust out your PLA filament and 3D Printer and start printing our beautiful casing!

If you don't have a 3D Printer, you can always send your .stl files to a 3D Printing manufacturer and have them ship it to you. Similar to how you would design and receive a circuit board by sending the gerber files.

Step 5: Setup the App Using Blynk

Download Blynk from the app store and at this point it is pretty simple. The internal guide provided in the blynk app is extremely easy and intuitive. Go ahead and create a new project and add 4 gauge displays.

To change their virtual wire, just tap on it while it is not running and select V1,V2,V3,V4. Note that you need to ensure it is correctly selected according to the arduino firmware.

Remember to replace the OAuth token with the placeholder in the arduino firmware.

Step 6: Tuck Everything In

Ensure that the firmware has been loaded properly before you proceed with this step. Note that in the source code I've commented on where you should make changes to accommodate your WiFi SSID, Password, different DHT11 pin connection and the Virtual Wire it will be sending towards (more on that later).

The design of the casing should fit perfectly if your 3D Printer has done everything correctly.

Step 7: You're Set!

Just set one of the device indoor and one outdoor to monitor difference in temperature and you can decide whether you should keep your window opened or closed.

The casing is not water resistant so keep it under a hood or a roof.

Hope you like this project, see you folks next time!



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