[JT118]

Hi JT118

No CO2 Display on board LCD but that seems to be the same for all?

It should be shown on the LCD too. Do you get CO2 data on the Pro2 PLUS receiver?

It is On the Pro Plus RX but not on AQI LCD. I notice this in some others photos on the AQI thread it appears to be missing there as well.

so far, but maybe it takes a few hours to work?

First data should start to be displayed after just 10 minutes. Please check Pro2 PLUS user configurable settings:
"Enable_Internet"  and "Enable_AQMtoThingSpeak" should be enabled.

I think all my settings are OK but the Wifi module does not blink with a blue light, must be my soldering?!>

[JT118]

It is working on my 1.4 board:

https://thingspeak.com/channels/328043


But the TFT screen is not working.

I have got my 1.3 board going, my poor soldering on the ESP8266.

[werk_ag]

But the TFT screen is not working.

I sent you a PM about this, please note that positions of the TFT pins on V1.4 boards are slightly different than in v1.3 boards. LED+ pin is one position to the left.

[werk_ag]

It is working on my 1.4 board:

https://thingspeak.com/channels/328043

Yes, it is.

It would be nice if all of us would add the word "weatherduino" to our existing tags at ThingSpeak. That will make easier for any of us find the others WeatherDuino's Air Quality Monitor channels, by just clicking on the WeatherDuino tag

[JT118]

"Weatherduino" Tag has been added. My CO2 readings are rather high. I think there must be a calibration issue. 700 to 800ppm is rather high (about the same as a CO2 enriched greenhouse) a number in the early 400's is more realistic.

https://www.co2.earth

https://www.scientificamerican.com/artic...d-for-co2/

[JT118]

Just been checking all our readings for CO2:

https://thingspeak.com/channels/328043

https://thingspeak.com/channels/317451

https://thingspeak.com/channels/327199

https://thingspeak.com/channels/333695

https://thingspeak.com/channels/328383

it seems 327199 is the most consistent and realisitic CO2 reading. Of course there are things that can alter this fairly substantially; inside, outside, If inside how many people in the house, if outside is it near a busy road, a gas boiler, a bushfire, is it winter lots of gas boilers running, is it summer CO2 absorbed by growing plants, etc. Nonetheless I would expect that generally CO2 should run in the low 400's, occasionally rising but not much above 450ppm. It seems all of us are outputting figures substantially above that.


I assume we are all using the MH-Z19 as below.

http://www.ebay.co.uk/itm/1Pcs-Mh-Z19-0-...1826725122

What is 327199 doing correctly?

See here for some Australian (Tasmania) Graphs.

https://www.theguardian.com/environment/...-no-return

[werk_ag]

Hi JT118,

I'm glad that you bring this theme to the public forum, some time ago I tried  launch a discussion about this matter on the Developers forum, however without success...

Looking to the data of my CO2 graphs, "apparently" they seem wrong... Initially I expected a more constant reading. We read everywhere that the CO2 median levels on the earth are around 400ppm. So what's going on?

I'm sure that you are the most capable person to investigate about this matter, and bring us a well written explanation.

It a fact that the mean CO2 value on earth is a value around 400 ppm, however this value is a global value, and local measures, depending on location and time of the day may vary greatly.

I already have searched a lot abbout this matter, and it seems that our readings are not so wrong as it seems at first sign.

If you carefully look at my readings, you will see that the variations follow a pattern: during the day (when there is light), they are always close to 400ppm, and start to increase at the end of the day, lowering again during the next day time.

Googling for it, I found on the internet many explanations to this behaviour. All of them refer that this behaviour is related to the photosynthesis process, so its possible that all of us that live in densely arborized zone will got high CO2 readings at night.

... in the absence of light there is no photosynthesis, when the photosynthesis process can't happen, the plants release more CO2 (at night they are only breading, just like us)

I'm counting with you to further investigations on this matter.

A special note regarding the MH-Z19:
* The minimum reading is 400ppm
* It is factory calibrated, but also allows calibration, however it should not be done, unless you can do it in an environment where you know exactly the CO2 level

[JT118]

You are correct in your assumption that CO2 levels will rise at night in summer, as they do in both day and night in the winter, for the same reason, a lack of photosynthesis.

CO2 + H2O + photons → [CH2O] + O2

the diurnal range will be in the region of 50ppm due to the photosynthetic effect, and as winter sets in that diurnal difference should reduce though the overall level will rise, (the famous NASA Earth Breathing Video)

https://www.youtube.com/watch?v=x1SgmFa0r04

as photosynthetic activity shuts down, (and people switch on their heating). However the range will not be in region most of us are reading from our sensors where the ranges are in 100s of ppm. day to night. (also note the CO emissions (not CO2) from bush fires in sub Saharan Africa in September. I use to live there, and when flying in September one would fly in through the relatively static inversion layer (hot air meeting cold) through about 50metres of smoke sitting in the atmosphere at about 3000 feet above ground level.)

https://books.google.co.uk/books?id=KaJH...g=PA294&dq

See page 295 of this book.

I am not sure if there is some other phenomena forcing this huge range, or perhaps it is the way the sensor is being read. You are also correct to say that the CO2 levels at Mauna Loa and Cape Grim are global readings, these stations are purposely located far from cities and in places where the prevailing wind comes across large expanses of ocean and is not affected by local pollution from citiies etc.

However despite all this if the sensor is outside and away from immediate sources of CO2 (boilers etc) the we should read between 400+ppm midday in summer to perhaps 500+ppm (maybe a little more) in winter at night. As can be seen from below wind has as much or more effect on CO2 diurnal ranges.

http://meteo.lcd.lu/papers/co2_patterns/...terns.html

But we still see diurnal ranges seldom exceeding 100ppm. and normally a lot less.

http://www.csiro.au/greenhouse-gases/

It seems the sensors are reading the correct pattern but perhaps most are reading the highs very high and lows about right.

[werk_ag]

Thank JT118 for this valuable info

the diurnal range will be in the region of 50ppm

So it seems that the diurnal range that we are getting is far above this value.

I am not sure if there is some other phenomena forcing this huge range, or perhaps it is the way the sensor is being read.

According to the manufacturer manual:

"You can read gas concentration via UART directly, no need to calculate."

This is what the software is doing, issue a command that asks for a reading, an then read the answer.
There is checksum to verify the validity of answer, if it fails the answer is rejected. There isn't any calculation involved.

I wasn't aware of the normal diurnal range, but since the beginning that the measured diurnal range seemed too large.
I have already asked to the others, info about their model of the MH-Z19, but I get no answer. This could be important, because there are two models of this CO2 sensor, mine is the first model, called only by MH-Z19, but there are also a newer model called MH-Z19B.

[qldbureau]

I have already asked to the others, info about their model of the MH-Z19, but I get no answer. This could be important, because there are two models of this CO2 sensor, mine is the first model, called only by MH-Z19, but there are also a newer model called MH-Z19B.

This is the unit I bought. Unfortunately I cannot read the label, as I did not realise I stuck it down in its test bed position over the label, with a blob of Blu-Tac, and now I found has largely dissolved the ink.
If I can fully trust the description, it should be the first version, not B.
My setup is indoors presently whilst I am gathering and setting up external enclosures.