MH-Z19 CO2 sensor

[Daniel Oliveira]

Hello,

I finally got this sensor to work but instead I use this lib: https://github.com/nara256/mhz19_uart
Another very useful source of information is this: https://revspace.nl/MHZ19#command_0x62_.28device_name_.2F_id.29

Take note that is the MH-Z19B the methods isWarming() and getStatus() do not work.

Can you please share the values that you are getting? I'm getting around 1500ppm and it is alarming by these website standards:
https://www.engineeringtoolbox.com/co2-comfort-level-d_1024.html
https://www.kane.co.uk/knowledge-centre/what-are-safe-levels-of-co-and-co2-in-rooms

I didn't have the opportunity yet to get the sensor outdoors.

Thank you in advance

[alowhum]

I get values between 300 and 1500 I believe.

[noli]

Hi there,
I'm currently trying to make it work (on an arduino pro mini 3.3), but won't succeed.
I keep having the following output :

CO2 - Sending data request to sensor.
1 - 40 - 1 - 0 - 1 - 21 - 3 - 15 - 0 - END
Wrong starting byte from co2 sensor! (should be FF)
Co2 - PPM = -1
Co2 - zzzzZZZZzzzzZZZZzzzz

Sometimes the second value is different but the first one is always 1. And obviously 1 is not FF :) . However I don't understand what's wrong in there.

I have to mention I'm using the MH-Z19B, and powering it with 5V, as opposed to the 3.3v of the arduino.
I also tried with the mhz19_uart lib, but didn't go further with it as the samples where not working out of the box with the z19B. Will probably give it another try, though...

[noli]

Hmm, tried wiht the uart lib, after removing the unsupported parts, no luck either.

[skywatch]

@alowhum

Thank you for posting this..... I tried it today and it works well! :)

To test it I wondered where to get a source of co2 from, then an idea hit me......So I opened a beer :)
I tipped it into a pint glass and drank most of it. Then, when I remembered the reason for opening the beer, I dangled the sensor into the glass, well above the liquid, placed my hand on top to seal it and swirled the beer around to release the co2 that makes it fizzy - result?

Well in the room I was getting a constant reading of 395, but in the beer glass it went to 1711, 3055, 5000 !!! - So it works!

Removing the sensor back to normal room air and it dropped back to 396 within 90 seconds.

So quite impressed at the moment. So far this it the most expensive sensor I have used. About $18 for the 'B' version.

[alowhum]

@skywatch you're welcome. Did you use a 5v or 3.3v Arduino? I still have to figure out if this sensor's serial port is 5v tolerant. The MH-Z14 is.

[Nca78]

@alowhum said in MH-Z19 CO2 sensor:

@skywatch you're welcome. Did you use a 5v or 3.3v Arduino? I still have to figure out if this sensor's serial port is 5v tolerant. The MH-Z14 is.

Datasheet (for model B) says "3.3 V(Compatible with 5V)"

[Joseph Gill]

I know I'm resurrecting an ancient topic here...

How have these sensors worked? I need the ability to monitor CO2 and evacuate it when it get's too high. This isn't super mission critical stuff here but I would like to use a sensor like this to get a better idea of how much air I need to evacuate.

I'm looking at building something to interface with a MQTT broker to control other IoT devices on my hub. How hard would it be to add that capability to an arduino type solution like this one here?

I'm more familiar with RPi's but am interested in this because of the "simplicity".

Thanks!

Cheers,

Joe

[skywatch]

@Joseph-Gill My sensor has taken a few knocks but still works really well. I have got another one now to use in the car (when I get around MYSing the car that is).

The last readings from my sensor.....

Readings are high as the sensor is currently too low to the ground. I will attend to this when I have time to make it into a cased unit.

[TRS-80]

@Joseph-Gill said in MH-Z19 CO2 sensor:

"simplicity"

Welcome to the forums, Joseph.

I am glad to see you put "simplicity" in quotes. Personally, I think that the level of difficulty that is portrayed towards new people (i.e., "it's easy!") is a little misleading. It is easy if you have "The Knack" but perhaps not so for everyone.

@Joseph-Gill said in MH-Z19 CO2 sensor:

How hard would it be

I think this depends mostly on an honest evaluation of your own skills. You will need to have at least basic understanding of the technologies involved: radio propagation, electronics, coding, etc...

Now, all of this can be learned of course, especially if you have interest, and time...

So another part of it is also your expectations. If you need something "right now" then you might be happier to go buy something "off the shelf."

OTOH, if you enjoy tinkering, learning, and want to eventually be able to build all different sort of devices exactly to your specifications and needs, then MySensors might be the right thing for you.

IMO, I think the best approach is to take this as a hobby, slowly acquiring parts (the least expensive ones take a long time to come from China!) as well as knowledge, and eventually increasing your capabilities over a long period of time. And you will learn (IMO) very valuable skills in the process...