DIY Video Tutorial: Build Your Own CO₂ Traffic Light

DIY CO₂ Traffic Light by E+E Elektronik

CO2 traffic lights are used to monitor the indoor air quality. They measure the CO2 concentration indoors and output a signal when you need to air the room. A regular supply of fresh air not only improves your sense of well-being, but also reduces the risk of infection from virus-laden aerosols. In the fight against the Corona pandemic, the use of CO2 traffic lights in schools or day schools is even expressly recommended by experts and authorities. But the use of a CO2 traffic light also makes sense in private households in order to air the rooms in an energy-efficient way whenever needed.

Discover how to build your own CO2 traffic light here!


"Do it Yourself" – CO₂ Traffic Light Build Instructions 

Whether as a school project or for home use, with the right components for the measuring system electronics and an Arduino Nano as the control unit, you can build your own CO2 traffic light.

The video instructions show you how to do so:

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Below you will find the material list, the circuit diagram and the Arduino sketch for your DIY CO2 traffic light.

Good luck with your build!

List of Materials and Circuit Diagram

To build the CO2 traffic light, the following materials and components are required:

1 pc. EE895-M16HV1 CO2 sensing module  (can be ordered here)
1 pc. Arduino Nano
1 pc. LCD display 16x2, Arduino compatible (with I2C adapter)
1 pc. USB cable (A male to mini-B)
1 pc. LED green
1 pc. LED yellow
1 pc. LED red
1 pc. 330 Ω resistor 
2 pcs. 10 kΩ resistor
4 pcs. M3 x 16 screws (for display)
8 pcs. M3 nuts
1 pc. Cardboard box
Cover for cardboard box (optional)
Male pins, female headers (in sufficient quantity)
Wire, breadboard (in sufficient quantity)


Download list of materials

Download circuit diagram

Open Link in LightboxCircuit diagram DIY CO₂ guard
Circuit diagram DIY CO₂ guard (click to enlarge)

Arduino Software (IDE) and Sketch

Step 1:
Download Arduino Software (IDE):
Recommended version: >1.8.7

Step 2:
Use the USB cable to connect the Arduino Nano to the PC.
Select the "Arduino nano" board, processor "ATmega328P" (old bootloader) and the correct COM port in the Tools menu.

Step 3:
Copy and upload the file “CO₂_Guard_Arduino_Sketch.ino” to the Arduino IDE. 

Download Arduino Sketch



Enclosure for the DIY CO2 Traffic Light

A cardboard box or similar measuring approx. 12 cm x 9 cm x 5 cm (WxHxD) is perfect as the enclosure for the CO2 traffic light. 

TIP: Use the dimensioning template to transfer the required openings for the LCD display and the LEDs precisely to the enclosure.

Download template


Explanations on Measured Value Scale

The CO2 traffic light's LEDs indicate the air quality based on the measured CO2 values:

  • GREEN = Good air quality  
    CO2 content <1,000 ppm
  • YELLOW = Medium air quality
    CO2 content 1,000 – 1,400 ppm
  • RED = Bad air quality
    CO2 content > 1,400 ppm

The limit values can be individually adjusted in the Arduino programming. Instructions are provided as a comment in the Arduino Sketch (ino file).

DIY CO₂ guard display
The air quality is indicated by the LED colour and the CO₂ concentration is shown on the display.

CO2 Traffic Light Also Measures Temperature and Pressure

By the way, the CO2 traffic light not only measures the CO2 concentration but also the temperature and the ambient pressure.

The reason for this is that the EE895 sensing module has integrated temperature and pressure sensing elements in addition to the CO2 sensing element.

The measured temperature (°C) and the ambient pressure (hPa) are shown in the second line of the LCD display (alternating with the CO2 content).

Open Link in LightboxEE895 CO₂ sensing module
In addition to CO₂, the EE895 sensing module also measures the temperature and ambient pressure.
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