The CO2-Ampel shows a color according to the carbon dioxide (CO2) concentration and application. When the color is blue or green the CO2 concentrations is good/low. Yellow indicates an increased concentration and at red a ventilation should be done. The blue color range can be used for orientation when the ventilation can be stopped and the CO2 concentration is low. Fresh air has a CO2 concentration of about 400ppm.
Power is supplied via the USB-C connector (4.3-5.3V) and on power-up the sensor needs approx one minute till a valid value is displayed. If the color does not look correct (e.g. not blue in fresh air), then recalibrate the device. The Sensirion SCD30 sensors are shock-sensitive and can under certain circumstances be adjusted wrongly by shocks.
The brightness can be adjusted with the Switch button. A long press on Switch (>3s) will start the WiFi AP mode.
The light sensor is checked every hour and when it is dark, the brightness is reduced.
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The device should be placed in the middle of a room at a height of approx. 1.5m and with distance to people (exhalation air) and outside of window and door areas. In the area of strong airflows (draft), the traffic light usually shows significantly fluctuating values and therefore this should be avoided.
To start the service menu, hold down the Switch button on power-up or hold the Switch button and short press the Reset button.
The LEDs light up violet shortly and then the function can be selected using the Switch button and confirmed with a long button press (>2s). After 10s the currently selected function is also started automatically.
The LEDs show the current CO2 concentration as follows:
The CO2 sensor is pre-calibrated by the manufacturer and according to our tests, it has an accuracy of +/-50ppm. Therefore we recommend a calibration after some months at the earliest and then once every year. In some cases a calibration is required after installation, because the Sensirion SCD30 sensors are sensitive to shocks.
A calibration can be done directly on the device if it is operated in fresh air (400ppm CO2).
The current sensor data can be read via USB and a terminal program (e.g. HTerm, PuTTY, minicom or picocom) with the connection parameter 9600 Baud, 8N1, Newline at:LF.
Procedure (firmware v9+)
Operate the CO2 traffic light in fresh air, outdoors or directly at an open window (protected from wind). Do not place the device in a container during calibration, because carbon dioxide can accumulate there.
Start the service menu by holding down the Switch button on power-up or by holding the Switch button and short pressing the Reset button.
The sensor data can be read out and settings can be changed via the serial interface using a terminal program. e.g. HTerm, PuTTY, minicom, picocom or Serial-USB-Terminal Android App
Connection parameters: 9600 Baud, 8 Data, 1 Stop, Parity: None, Newline at: LF
R=1- Remote control on, required once before sending commands
R=0- Remote control off
V?- Get firmware version
S=1- Save settings
L=RRGGBB- LED color (000000-FFFFFF)
H=X- LED brightness (0-FF)
B=1- Buzzer activated and on for 500ms
B=0- Buzzer deactivated
T=X- Temperature offset in °C (0-20)
T?- Get temperature offset
A=X- Altitude in meters (0-3000)
A?- Get altitude
C=1- Calibration to 400ppm CO2 (at least 3min operation on fresh air required before command)
1=X- Range 1 start: green (400-10000)
2=X- Range 2 start: yellow (400-10000)
3=X- Range 3 start: red (400-10000)
4=X- Range 4 start: red flashing (400-10000)
5=X- Range 5 start: red flashing + buzzer (400-10000)
c: 600 t: 20.5 h: 50.5 l: 1024 p: 1010.50 u: 20.55
For models with a WiFi/WLAN module, the current sensor values can be accessed via a local website.
A long press on Switch (>3s) will start the WiFi AP mode.
After connecting to the network, the website can be accessed:
The login data for an existing network can also be entered on this page, so that the CO2 traffic light connects to it and queries an IP address via DHCP.
http://192.168.1.1/json (use the respective IP address)
http://192.168.1.1/cmk-agent (use the respective IP address)
If the WiFi/WLAN module is not actively used, then it is recommended to set the temperature offset to a lower value (+4°C to +6°C).
Models with LoRa have a transceiver for data exchange using the LoRa network standard.
There is currently no support for this in the standard firmware. But the Arduino CO2 traffic light boards package already contains all required libraries.