IoT CO2 Monitor System

IoT CO2 Monitor is our latest project of the CO2 Series. It comes in the smallest size, fitting right in your pocket, yet packed with the most powerful features. It reacts within seconds to changed conditions.

The portable battery-powered device measures CO2, humidity and temperature, and upload the data to the Cloud to be shared with everyone. The QR code on display allows people to scan and view the data anytime from anywhere through phones, tablets or computers.

If you breathe anywhere near the sensor, it will report the increase almost immediately. An OLED is added to display the readings, alongside with an addressable LED strip for realtime visual feedback.

Credits: Sam Berman, Mitchell Neo, Donnie Chen, Shin

Demo video:

Why this project

Proper indoor ventilation will move fresh air into the room and disperse aerosols. In a room filled with people, CO2 will rise if the doors and windows are closed and it will drop if they are left open. That feeling that "It's stuffy in here" indicates that not only CO2 is rising but also virus-laden aerosols. But how do we know what is proper and safe? Enter the CO2 sensor.

This CO2 sensing device can provide a warning system that notifies you to take action to improve ventilation or reduce the number of people in the room. Hence, it reduces your risk of exposure to Covide-19. It is a marker for proper air ventilation.

While you can buy commercial CO2 devices, a homemade version is not rocket science and you'll gain a better understanding of how it works. Plus, you can customize it in all kinds of ways. With Covid-19, you work is bound to find its use in a crowded city like Hong Kong, be it in a classroom, bus, subway, bedroom, etc.

While you can buy commercial CO2 devices, a homemade version is not rocket science and you'll gain a better understanding of how it works. Plus, you can customize it in all kinds of ways. With Covid-19, you work is bound to find its use in a crowded city like Hong Kong, be it in a classroom, bus, subway, bedroom, etc.

C02 Monitor Family Members

CO2

CO2 is a gas measured in parts per million (ppm). In a typical room with nobody in it, CO2 measures around 430ppm, same as outdoor air. While we breathe, we are emitting CO2. CO2 level rises when we are speaking, dancing or singing. If you are speaking loud, you are emitting more CO2.

In this project, I used three colors of LEDs to create a warning system. Green light means everything is okay. Yellow means you should open the window. And red is the ultimate warning. The brightness of the three colors are reflective of the CO2 density. Below are the threshold values:

> 3000 PPM ALERT RED

> 2000 PPM BAD RED

>1000 PPM FAIR YELLOW

<1000 PPM CLEAR GREEN

Versions Comparision

CO2 Monitor V1

Our first version running on Arduino Uno comes with a LCD2004, NeoPixel ring and CO2 sensor. It uses two recargeable 18650 batteries. The device is presented in a big, transparent plastic box.

CO2 Monitor Compact V2

In the second version we opted for an OLED display and Arduino Nano, which greatly shrink down the size to one half. It has built-in 18650 battery charger so that charging is as easy as plug and play.

CO2 Matrix Display V3

The thrid generation is designed for indoor usage. The 64x32 RGB Matrix Panel displays four emojis, making the project really cool to look at and easy to understand. It has CO2 readings to the left and emoji to the right. We use Arduino Mega to control the panel since the popular Uno doesn't have enough memory and pins.

IoT CO2 Monitor V4

The latest version is 1/6 the size of version 2 and 1/12 of version without sacrificing any features. In fact, it is the strongest of all. Apart from showing relevant data on the display, it also boasts a QR code for people to scan. The data it collected are sent over the internet for sharing so that you can monitor the air quality no matter where you are.

HARDWARE

At the core of the CO2 monitor is a microcontroller ESP32 that connects to the sensor, OLED display and addressable LEDs. It can be powered either by battery or through USB. To attain a smaller size..

Sensirion SCD30, a high performance CO2 sensor that costs about HK$350. It is a nondispersive infrared (NDIR) optical sensors that has two channels that use infrared light to detect CO2 in the air. The infrared light that's emitted is absorbed by the CO2 molecues. The more CO2 in the tube, the less infrared ligth is detected.

8x WS2813 5050 RGB LEDs ring is equipped with a single data line with a very timing-specific protocal requring real-time microcontroller with fast processor. Each WS2812 is addressasble as the driver chip is located inside the LED. It runs on 3.3V.

To avoid too many wires for the small OLED monochrome display, the interface we use is I2C . The I2C OLED is very easy to get up and running because it has built in level shifting and regulator. The OLED and driver require a 3.3V power supply and 3.3V logic levels for communication. Built into the OLED driver is a simple switch-cap charge pump that turns 3.3v-5v into a high voltage drive for the OLEDs. You can run the entire display off of one 3.3V supply.

Further improvements

Since IoT CO2 Monitor is made to be portable, it will be great if it is waterproof and has a screen protector. To make it more attractive, try decorating the 3D printed case in different colors.