VOC SGP40 DHT11

Measure the air quality (VOC) using the SGP40 and DHT11 sensors.

Video

There is a video associated with this repo. Please watch the video, it explains how to use this repo and everything you need to know for the project.

Components required

Micro-controller

For the micro-controller, ESP32 was used, but the ESP8266 will work as well.

Sensors

• SGP40, used to "sense" the air quality, it gives the quality of the air in terms of the raw resistance.
• DHT11, since the quality of the air changes with the temperature and humidity, this sensor is used to obtain those two measurements.

Arduino

• For the Arduino sketch, please refer to the /VOC_SGP40_DHT11 directory.

Changes you need to make

• VOC_SGP40_DHT11.ino, change the WiFi name and password, and also make sure the DHT11 pin matches with your connection.
• /data/index.html, change the following:
  • username: "Your-GitHub-username"
  • password: "Your-GitHub-password"
  • token: "Your-GitHub-token" (I go through how to obtain your token in the video)
  • repo: "Your-GitHub-repo"

Optional changes

• In data/index.html,
  • dataRate rate at which data is obtained from all the sensors in milliseconds. (Default 1000).
  • save whether to save/backup sensor data to GitHub. (Default true)
  • saveRate rate at which all sensors data points are saved to GitHub in seconds. (Default 120).

Libraries needed for the Arduino sketch

• Two of which, can be installed directly from the Arduino IDE (Tools>Manage Libraries...):
  • Adafruit SGP40 Sensor
  • DHT sensor library by Adafruit
• Libraries needed to be installed manually (great tutorial on how to install them can be found here):
  • SPIFFS for ESP32 or SPIFFS for ESP8266
  • AsyncTCP
  • ESPAsyncWebServer

Wiring diagram

How to use

• When the micro-controller is turned on, its local IP address will be printed in the serial monitor, navigate to the IP address in a web browser to see the measurements.
• When the data is saved (based on the saveRate you set), it will create a directory, named with the date and time of when the micro-controller was turned on.
• The data will be saved in a text file with each value seperated by a space, where each line is a data point. The values saved (in this order):
  • Date/Time in miliseconds.
  • VOC index
  • SGP40 raw resistance
  • Humidity
  • Temperature
  • Illustration on how the data is saved: