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 with 5V (4.3-5.3V). On power-up the sensor needs approx. 30s until a valid value is displayed (standard measuring interval: 3s).

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 and the measuring interval is increased to 30s.

  • 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.

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 or picocom).

  • Connection parameters: 9600 Baud, 8 Data, 1 Stop, Parity: None, Newline at: LF
  • Commands
    • R=0 - Remote off
    • R=1 - Remote on, required once before sending commands
    • S=1 - Save settings
    • L=RRGGBB - LED color (000000-FFFFFF)
    • H=X- LED brightness (0-FF)
    • B=1 - Buzzer on for 500ms
    • T=X - Temperature offset in °C (0-20)
    • A=X - Altitude in meters (0-3000)
    • P=X - Pressure in hPa (0 or 700-1400), overwrites the altitude compensation
    • C=1 - Calibration to 400ppm CO2 (at least 3min operation on fresh air required before command)
    • 1=X - Range 1 start: green (400-40000)
    • 2=X - Range 2 start: yellow (400-40000)
    • 3=X - Range 3 start: red (400-40000)
    • 4=X - Range 4 start: red flashing (400-40000)
    • 5=X - Range 5 start: red flashing + buzzer (400-40000)

Firmware

Update Instructions

  • Connect the device to a computer via USB.
  • Press the reset button twice within 500ms.
  • A new USB mass storage device will appear. (On problems try another USB cable, no longer than 1m.)
  • Copy the new firmware file (co2_xxx.bin) to this device/drive (on Windows). On Linux/Mac the dd command can be used for the writing: dd if=co2_xxx.bin of=/media/CO2AMPEL/FW.BIN conv=notrunc
  • The device will update itself and restart with the new firmware and the WiFi and range settings are reset.

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.

  • 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)
    • 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 and Temperature-Offset

  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

Calibration

The SCD30 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.

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.
    • 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 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). 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.