Getting Started

Introduction

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.

CO2-Ampel

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.

  • for covid prevention

    • up to 599 ppm -> light blue
    • 600 to 799 ppm -> green
    • 800 to 999 ppm -> yellow
    • 1000 to 1199 ppm -> red
    • 1200 to 1399 ppm -> red flashing
    • 1400 ppm and higher -> red flashing + buzzer

  • against tiredness

    • up to 599 ppm -> light blue
    • 600 to 999 ppm -> green
    • 1000 to 1199 ppm -> yellow
    • 1200 to 1399 ppm -> red
    • 1400 to 1599 ppm -> red flashing
    • 1600 ppm and higher -> red flashing + buzzer

Location

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.

Service Menu

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.

  • Software v22 and upwards
    • 1 violet LEDs -> Self test
    • 2 violet LEDs -> Fresh air test
    • 3 violet LEDs -> Altitude compensation + temperature offset + buzzer
    • 4 violet LEDs -> Calibration on fresh air
  • Before v22
    • LED 1 -> Self test
    • LED 2 -> Fresh air test
    • LED 3 -> Altitude compensation and temperature offset
    • LED 4 -> Calibration on fresh air

Self Test

  1. Buzzer
  2. LEDs red
  3. LEDs green
  4. LEDs blue
  5. LEDs white (only plus version)
  6. Sensor test (all LEDs have to show green)
    • LED 1 = Light
    • LED 2 = CO2 (100-1500ppm)
    • LED 3 = Temperature (5-35°C) and Air Pressure (700-1400 hPa)
    • LED 4 = Humidity (20-80%)

Fresh-Air Test

The LEDs show the current CO2 concentration as follows:

  • up to 299 ppm -> red
  • 300 to 349 ppm -> yellow
  • 350 to 450 ppm -> blue
  • 451 to 500 ppm -> yellow
  • 501 ppm and higher -> red

Altitude-Compensation + Temperature-Offset + Buzzer

  1. Altitude compensation adjustable via Switch button (timeout after 10s or 2s long press)
    • 0 red LEDs = 0m
    • 1 red LEDs = 250m
    • 2 red LEDs = 500m
    • 3 red LEDs = 750m
    • 4 red LEDs = 1000m
  2. Temperature offset adjustable via Switch button (timeout after 10s or 2s long press)
    • 0 yellow LEDs = 0°C
    • 1 yellow LEDs = +2°C
    • 2 yellow LEDs = +4°C
    • 3 yellow LEDs = +6°C
    • 4 yellow LEDs = +8°C
  3. Buzzer adjustable via Switch button (timeout after 10s or 2s long press)
    • 0 green LEDs = Buzzer deactivated
    • 1 green LEDs = Buzzer activated
  4. End: the LEDs light up blue and the buzzer sounds for a short time

Calibration

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.

Video of the process

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.

  1. Service menu: 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.
    • Software v22 and upwards
      • 1 violet LEDs -> Self test
      • 2 violet LEDs -> Fresh air test
      • 3 violet LEDs -> Altitude compensation + temperature offset + buzzer
      • 4 violet LEDs -> Calibration on fresh air
    • Before v22
      • LED 1 -> Self test
      • LED 2 -> Fresh air test
      • LED 3 -> Altitude compensation and temperature offset
      • LED 4 -> Calibration on fresh air
  2. Short press the Switch button 3 times so that all 4 LEDs or the 4th LED next to the Reset button lights up.
  3. Wait 10s or hold down the Switch button for at least 2s (long press).
  4. Calibration (at least 2 minutes, maximum 15 minutes in a stable environment). Two LEDs show the current uncalibrated CO2 value: blue up to 500ppm, green up to 750ppm, yellow up to 1500ppm, red from 1501ppm
  5. After a successful calibration, the LEDs light up blue and the buzzer sounds for a short time. Then the device will go into normal operation.

Serial Interface (USB)

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

  • Commands

    • 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)

  • Sensor data

    • c = CO2 value in ppm
    • t = Temperature in °C
    • h = Humidity in %
    • l = Light (1024=bright)
    • p = Pressure in hPa
    • u = Temperatur in °C (pressure sensor)
    c: 600
t: 20.5
h: 50.5
l: 1024     
p: 1010.50
u: 20.55

WiFi/WLAN

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: http://192.168.1.1 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.

JSON endpoint: http://192.168.1.1/json (use the respective IP address)

Checkmk endpoint: 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).

LoRa

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.