Introduction: Illuminance Monitor With ESP8266 - IoT

This project will help you create an illuminance monitor using an ESP8266 SoC and a illuminance sensor (TSL2561) with next capabilities:

  • Measure illuminance
  • Monitor illuminance from your smart phone

To complete this project you will have to create three things

  • Hardware - Basically you have to hook up the illuminance sensor to the ESP8266 board and upload the Arduino code.
  • Setup IC2Cloud API - Use IC2Cloud platform to communicate between the sensor and smart phone
  • Mobile App - Create the mobile App using AppInventor to monitor your illuminance

This project can be easily extended to monitor multiple sensors and if combined with a relay, turn ON/OFF the light based on the illuminance threshold you could set from the smart phone.

Step 1: Get Your Materials

To complete this project you need a few things

  • A ESP8266 board. I recommend the Adafruit HUZZAH ESP8266 board. The main advantages are:
    • You get a FCC certified ESP8266 board
    • The ESPB8266 board has multiple pins exposed on the PCB
    • It has a voltage regulator on the board
    • It has buttons to trigger programming mode
  • An illuminance sensor. I used a TSL2561 from Adafruit
  • Some female to female cables
  • And optional if you want to make the module stand alone a USB connector and a USB power supply....and an enclosure.
  • To upload the Arduino code on the ESP8266 board you need a programming cable. I recommend this one from Adafruit.

Step 2: Wiring

The wiring is very simple. You have a diagram above that shows you how to do it. To be more specific you need to do four connections:

  • TSL2561 - Vin Pin ---> HUZZAH ESP8266 - 3V Pin
  • TSL2561 - GND Pin ---> HUZZAH ESP8266 - GND
  • TSL2561 - SDA Pin ---> HUZZAH ESP8266 - #4 Pin
  • TSL2561 - SCL Pin ---> HUZZAH ESP8266 - #5 Pin

To be able to program it you need to connect the programming cable too. If you use the Adafruit cable I recommend then you just plug it in with the black wire to the GND pin as shown in the picture above. For more details how to program HUZZAH board with Arduino please go to Adafruit website.

Step 3: Prepare Development Environments

To program this project you will need three development environments:
Arduino IDE for ESP8266 - You will use this to create the "firmware" for your hardware. To set-up this please follow the tutorial on the Adafruit website.

IC2Cloud Wiring Cloud - You need this to create the communication channel between your sensor and the smart phone To set-up this go to and register. Once you did that go to this section to create an API password.

App Inventor - You need this to create your mobile App (Android). To set-up this please go to App Inventor website and press the button Create Apps. Follow the instructions on the website. You might need a Gmail address to authenticate there.

It might sound complicated but it is fairly fast to execute all these steps.

Step 4: Program the Hardware

To program the HUZZAH board I have opted for Arduino. A lot of people are familiar with this and considering the simplicity of the code I think it can do the job quite well. I assume you followed the instructions from Adafruit tutorial mentioned in the previous step.

There is one more thing to do. You have to download the libraries for the TSL2561 sensor from Adafruit website and follow their instructions to install them. Try their sample program before moving forward to make sure you have everything set-up properly.

I also assume you followed instructions to set-up you IC2Cloud account and the API access.

Once you did that please download the code I provide here (Illuminance.ino file from the ZIP file) and load it in the Arduino IDE. You have to modify a few things in the code to make it work

1. Modify "wifi ssid" string with your wifi SSID.

2. Modify "wifi password" string with your wifi password.

3. Modify "authentication" string with your authentication string for IC2Cloud API. Basically you have to append your user name, colon sign and password and encode the whole string using base 64 encoding. You can use this site to do that. For example if your user name is "user" and your password is "password" then you create this string:


and encode it using the tool from the link above. You should get



The password is the Api Password and not your login password. The user is your email you use for login.

There is one more thing that we recommend to change (but let's not do it until you understand the inner workings of the entire project) is the device Id. Last thing is to compile and upload the code on your ESP board. I assume you are familiar with Arduino IDE and once you are properly set up for the ESP board this should be easy.

Step 5: Verify Communication With the Cloud

Once you completed the previous step it is recommended that you verify the communication with the cloud.

If you are familiar with the debug in Arduino please use serial communication to check if everything is OK. You can also go to the Signal Manager on the IC2Cloud website to test if the ILLUMINANCE signal is sent to the cloud. The picture above shows you how to do it.

Please be aware that the signal is sent every few seconds.

If this is working properly then your hardware is up and running.

Step 6: Create the Mobile App

Using App Inventor from MIT you will create the mobile application. Once you are set-up with App Inventor you can go and import the Illuminance.aia file from the zip file. Once you open the project you should see the user interface designer. Switch to blocks section and you will see the picture above.

The only thing you need to change is your authentication string you have created in the previous steps.


The password is the Api Password and not your login password. The user is your email you use for login.

Once that is done you can build and download the App on your phone and you have everything ready. Follow the instructions on the App Inventor site how to execute the steps.

Step 7: Using the Illuminance Monitor

Open the mobile application you have created and you are gong to get a screen like the one above.

Here you can see your illuminance from the sensor.

This concludes the project. You have a illuminance monitor IoT style ;-)

You can improve it. Here you have a few ideas:

  • Add multiple sensors.
  • Add capability to monitor thresholds
  • Turn ON/OFF lights based on that threshold
  • ...and whatever you come up with ;-)

If you managed to get to this point then you have the basic skeleton for an illuminace monitor.

Please keep in mind this is experimental and you need to make your own judgements how you use this project.

Good luck!