Air Quality: CO2 Sensor MH-Z14

[mortommy]

thank you guys. :thumbsup:

[epierre]

@alexsh1 said:

@mortommy I'd strongly suggest you go for this sensor. It is expensive, but very-very precise and reliable. You can go for MQ-135 - this is what I did at the beginning. It is utterly useless and can probably be used in enclosed premises, but not in normal houses/flats as its reading are just jumping up and down.

agreed ! that comes with experience !

You can go for the MH-Z19 sensor - it is not much cheaper than MH-Z14 (or MH-Z14A).

it is now $3 difference

[flopp]

I am playing with a MH-Z19 and found this thread and the link in the first post is not working.

This is the correct link

https://github.com/empierre/arduino/blob/master/AirQuality-CO2-MH-Z14.ino

[alowhum]

Does the MH-Z14 code work for the MH-Z19 as well?

[Daniel Linder]

@alowhum. Yes it does. I've built a combined Co2, humidity and temp sensor using mh-z19 and dht22. it shows current values on an oled and reports back to openhab. will use a number of these for ventilation control.If anyone is interested I'll post the complete build when done (currently waiting for more components from China).

[alowhum]

The downside is that it uses pulse-width modulation to get the data out. This isn't a problem, but it soes mean that you are taking a digital value, turning it into an analog voltage reading that analog voltage with Arduino, and turning it back into a digital value.

I scraped together some code for the MH-Z19 that uses a serial connection to talk to the sensor instead. The sketch can be found here.

I also highly recommend getting the BME280 sensor for your humidity needs. It even gives you barometric data, so you can have your own weather prediction. A sketch that uses that sensor, and that is very easy to combine with the MH-Z19 sketch I just posted to, can be found here.

If you also want to integrate the best-buy dust sensor, have a look at this sketch that already combines the MH-Z19 Co2 sensor and the PMS-7003 air quality (fine dust) sensor.

[Daniel Linder]

HI,
I'll try your serial interface code later.
It seems to be an accurate sensor, however - the values are a bit "bouncy". I'll incorporate a "running average" on the measurements - to calm it down.
I am always tempted to add more sensors to the nodes, but in this case it is not possible.
My casing design would not even allow for one additional resistor... ;-)

[sola]

@Daniel-Linder Hi Daniel,

I would be quite interested in your Mh-z19 and DHT22 sensor node, I am building a similar one.

Please post the build if you still have it.

Many thanks.

[reinhold]

FWIW, some weeks ago I ported the MH-Z19 code (the serial interface, by default connected to digital pins 6 and 7) to NodeManager for use in my own little gas detection node (MH-Z19 and four MQ-... sensors). The MH-Z19 code is included in the 1.6 release of NodeManager, so if you are using NodeManager for your nodes, the MH-Z19 sensor should be really easy to set up and use.

[sola]

@reinhold said in Air Quality: CO2 Sensor MH-Z14:

orted the MH-Z19 code (the serial interface, by default connected to digital pins 6 and 7) to NodeManager for use in my own little gas detection node (MH-Z19 and four MQ-... sensors). The MH-Z19 code is included in the 1.6 release of NodeManager, so if you are using NodeManager for your nodes, the MH-Z19 sensor should be really easy t

Many thanks, I will check out NodeManager, looks like some really cool stuff.

[Gelisob]

Hello guys, could somebody clear up, what sensor to prefer. MH-Z14A vs MH-Z19 ?
Their price is very similar and kinda meh in comparison but which should one prefer and when?
I can see Z19 having some response time lower but power consumption higher...
Maybe someone here already made the comparisons and can share that useful information into this thread, so that others would also know what to pick and why?

Thanks :)

[alowhum]

Go with the Z19. Here's some ready made code:
https://forum.mysensors.org/topic/6528/mh-z19-co2-sensor/5