arduino sample sketch for ESP32 (here: LILYGO TTGO-T w. color oled) to measure CO2 concentration and display value on TFT, as well as use an 8-Bit RGB-LED-Ring to show/indicate CO2 concentration (ppm). In addition the value is published to an mqtt broker (using tls/ssl).
The LED-ring indicates green as good, yellow is warning level and red is critical.
It uses MH_Z19 sensor. During pre-heating (3 minutes) the LEDs show some spinning blue "wheel".
Recommendation from REHVA (Federation of European Heating, Ventilation and Air Conditioning associations, rehva.eu) for preventing COVID-19 aerosol spread especially in schools:
- warn: 800, critical: 1000 (https://www.rehva.eu/fileadmin/user_upload/REHVA_COVID-19_guidance_document_V3_03082020.pdf)
General air quality recommendation by the German Federal Environmental Agency (2008):
- warn: 1000, critical: 2000 (https://www.umweltbundesamt.de/sites/default/files/medien/pdfs/kohlendioxid_2008.pdf)
- arduinoota.h
- fastled.h
- tft_espi.h
- wifi.h
- pubsubclient.h
- softwareserial.h
- mhz.h
On a Linux Desktop one could use a command like the following to have the co2 value displayed "on-screen" and even swith color (via mqtt) using osd_cat.
threshold_val=1000
threshold=0
while read co2val; do
color='#0F0'
if [ $co2val -gt $threshold_val -a $threshold -eq 0 ]; then
color='#F00'
fi
if [ $co2val -lt $threshold_val -a $threshold -eq 1 ]; then
color='#0F0'
fi
echo $co2val | osd_cat -p top -A center -o 25 -i -50 -f '-*-liberation mono-*-*-*-*-40-*-*-*-*-*-*-*' -s 2 -c $color;
done < <(mosquitto_sub -h yourhost.de -p 8883 -u username -P passw0rd --cafile myCA.pem --cert client.crt --key client.key -t co2_ampel1/co2ppm)
OTA failed: no response from device (icmp type 3, code 13)
could be related to firewall rules, try either one of
$ sudo iptables -I INPUT -s 192.168.1.123 -j ACCEPT
$ sudo iptables -I OUTPUT -d 192.168.1.123 -j ACCEPT
or
$ firewall-cmd --zone=trusted --add-source=192.168.1.123
I read that people also have similar issues (destination unreachable) when on different wifi networks (2.4GHz vs 4GHz) but at least here that is not a problem (esp on 2.4GHz and laptop on 5GHz)
