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Read CO₂ concentration from mh-z19 sensor and handle it.

Connect RPi & mh-z19 as:

• 5V on RPi and Vin on mh-z19
• GND(0v) on RPi and GND on mh-z19
• TxD and RxD are connected to cross between RPi and mh-z18

Followings are example of cabling, but you can free to use other 5v and 0v Pin on the RPi.

pi@raspberrypi:~/mh-z19 $ gpio readall +-----+-----+---------+------+---+---Pi B+--+---+------+---------+-----+-----+ | BCM | wPi |   Name  | Mode | V | Physical | V | Mode | Name    | wPi | BCM | +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+ |     |     |    3.3v |      |   |  1 || 2  |   |      | 5v      |     |     | |   2 |   8 |   SDA.1 |   IN | 1 |  3 || 4  |   |      | 5v      |     |     |  <---- Vin |   3 |   9 |   SCL.1 |   IN | 1 |  5 || 6  |   |      | 0v      |     |     |  <---- Gnd |   4 |   7 | GPIO. 7 |   IN | 1 |  7 || 8  | 1 | ALT0 | TxD     | 15  | 14  |  <---- RxD |     |     |      0v |      |   |  9 || 10 | 1 | ALT0 | RxD     | 16  | 15  |  <---- TxD |  17 |   0 | GPIO. 0 |   IN | 0 | 11 || 12 | 0 | IN   | GPIO. 1 | 1   | 18  | |  27 |   2 | GPIO. 2 |   IN | 0 | 13 || 14 |   |      | 0v      |     |     | |  22 |   3 | GPIO. 3 |   IN | 0 | 15 || 16 | 0 | IN   | GPIO. 4 | 4   | 23  | |     |     |    3.3v |      |   | 17 || 18 | 0 | IN   | GPIO. 5 | 5   | 24  | |  10 |  12 |    MOSI |   IN | 0 | 19 || 20 |   |      | 0v      |     |     | |   9 |  13 |    MISO |   IN | 0 | 21 || 22 | 0 | IN   | GPIO. 6 | 6   | 25  | |  11 |  14 |    SCLK |   IN | 0 | 23 || 24 | 1 | IN   | CE0     | 10  | 8   | |     |     |      0v |      |   | 25 || 26 | 1 | IN   | CE1     | 11  | 7   | |   0 |  30 |   SDA.0 |   IN | 1 | 27 || 28 | 1 | IN   | SCL.0   | 31  | 1   | |   5 |  21 | GPIO.21 |   IN | 1 | 29 || 30 |   |      | 0v      |     |     | |   6 |  22 | GPIO.22 |   IN | 1 | 31 || 32 | 0 | IN   | GPIO.26 | 26  | 12  | |  13 |  23 | GPIO.23 |   IN | 0 | 33 || 34 |   |      | 0v      |     |     | |  19 |  24 | GPIO.24 |   IN | 0 | 35 || 36 | 0 | IN   | GPIO.27 | 27  | 16  | |  26 |  25 | GPIO.25 |   IN | 0 | 37 || 38 | 0 | IN   | GPIO.28 | 28  | 20  | |     |     |      0v |      |   | 39 || 40 | 0 | IN   | GPIO.29 | 29  | 21  | +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+ | BCM | wPi |   Name  | Mode | V | Physical | V | Mode | Name    | wPi | BCM | +-----+-----+---------+------+---+---Pi B+--+---+------+---------+-----+-----+

Full Set include followings:

• Setup script: Install & Setup following useful stuffs as:
  • mh-z19: A python module to read mh-z19 sensor.
  • PondSlider: A multipurpose versatile sensor handler for python, which read mh-z19 value and handle it.
  • autostart.sh: Utility making mh-z19 as system service to act periodically.

Install Full Set, download fromrelease

git clone https://github.com/UedaTakeyuki/mh-z19.git

Then, got to the folder and issuesetup.sh*

./setup.sh

Necessary settings including serial port enabling are taken place in this script.

For python 2.x

sudo pip install mh_z19

For python 3.x

sudo pip3 install mh_z19

In case you would use itwitout root permission, call pip without sudo as follows:

For python 2.x

pip install mh_z19

For python 3.x

pip3 install mh_z19

The differences of the interface between each Raspberry Pi model are resolved inside this module. For example, serial device name is difference between Raspberry Pi 3 and older model, but mh-z19 module automatically detect the model and read from appropriate serial device.

To use mh-z19, once you need to set up enabling serial port device on the Raspberry Pi.FollowingWiki page might be informative.Also, please referPyPi top page for detail.

pi@raspberrypi:~ $ sudo python3 -m mh_z19 {'co2': 668}

As above,sudo might be necessary because mh-z19 sensor value is read through serial connection and it request root permission in general.

The installedmh-z19 module is correspond thepondslider which is multiple & versatile sensor handler to save, send and to do other necessarysomething with the sensor value.

As an example, we introduce following use case:

• How to save sensor value to SD card as .CSV file.
• How to send sensor value to free Remote Monitoring Service.

The pondslider read sensorvalue bysensor-handler specified, and pass the values tovalue-handlers* which do something with it.

Both sensor and value handlers are python module. For more detail of handlers, please referthis.

This module correspond thepondslider which is multiple & versatile sensor handler to save, send and to do other necessarysomething with the sensor value.

In case you choicedFull Install mentioned above, in other words, you've donesetup.sh,the pondslider and there example handler's are already installed & setup.

You can do it withsave2strage value handler which is inhandlers/value/saver/save2strage, and configuration file to read from mh-z19 sensor and save by save2strage is prepared asconfig.save.toml on the mh-z19 installed folder.

On the mh-z19 folder By calling pondslider as follows;

sudo python -m pondslider --config config.save.toml

Then,/home/pi/DATA/co2.csv should be created and new line will be added for each call.

The MONITOR™ is a free Remote Monitoring Service to show latest data on the web.

Please refer anintroduction to grasp birds-eye understanding about MONIOR™.

A free account is available asfollow.Then, login and get aview_id, which is unique id to point a data area on the MONITOR™ to show latest value and chart, asfollow.

After get a value_id at your browser, return back to terminal of your Raspberry Pi, then you should set your this software to send measured value to the value_id. To do this, callsetid.sh command in the mh_z19 installed directory. Let's say your value_id isvpgpargj, issuesetid.sh command as follows:

./setid.sh vpgpargj

Then, call "pondslider" python script as follows:

pi@raspberrypi:~/mh-z19 $ sudo python -m pondslider{'co2': 742}co2{"ok":false,"reason":"ViewID not valid"}

Your time-series chart on the MONITOR™ display on the browser must be updated by the latest CO2 concentration value.

You can set it by autostart.sh command in the mh_z19 installed directory as follows:

./autostart.sh --on

You can turn off this as follows:

./autostart.sh --off

Also, You can check current status as follows:

./autostart.sh --status

For more detail, please refer thisblog.

The Pondslider also support ATT M2X. For detail, please referthis document.

Features about calibration (both MH-Z19 & MH-Z19B), detection range change (MH-Z19B) and ABC logic on/off(MH-Z19B) are implemented at version 0.2.1 or later.

I'm afraid I've just only implemented these without test due to lack necessary devices and apparatus for the test, fx: standard concentration CO2 GAS, also MH-Z19B module.If you have these devices or apparatus and try to use these functions generously, I really appreciate yourissue report regardless result were positive or negative.

• positive reportwith mh_z19b on a Raspberry Pi Zero W, Thank yourichteas75!

For detail please refer thiswiki.

TheRevspace/MHZ19 shows values undocumented on the official datasheets (MH-Z19,MH-Z19B). In accordance with this,--all option add these values in the return json value as follows:

sudo python -m mh_z19 --all{"SS": 232, "UhUl": 10752, "TT": 61, "co2": 818, "temperature": 21}sudo python3 -m mh_z19 --all{"TT": 61, "co2": 807, "SS": 232, "temperature": 21, "UhUl": 10752}

or callread_all() function as follows:

>>> import mh_z19>>> mh_z19.read_all(){'SS': 232, 'UhUl': 10738, 'TT': 61, 'co2': 734, 'temperature': 21}>>>

In case you should use specific serial device instead of Raspberry Pi default serial device which this library automatically select, for example in case to need to use /dev/ttyUSB0 forFT232 usb-serial converter asissue#12, you can specify serial device by--serial_device option as follows:

sudo python -m mh_z19 --serial_device /dev/ttyUSB0

See thiswiki.

See thiswiki.

See thiswiki.

Even if cabling seems no problem and uart seems to be prepateted well but you can't get sensor value. Asnincube8 suggested that thepull up by1-5kΩ register can be working solution. Thank younincube8!

The forum is avai athere. Any questions, suggestions, reports are welcome!

• How to Measure ROOM CO2 concentration with 20$ sensor "MH-Z19" and Raspberry Pi.
• Monitoring all over the world with 3G Network for not more than 10$ monthly payment.
• How to make shareable SD card by Raspberry Pi & PC.

• MH-H19B DataSheet version 1.5
• MH-H19 DataSheet version 1.0
• MH-H19B DataSheet version 1.0
• RevSpace

• 0.1.0 2018.09.13 first version self-forked fromslider.
• 0.2.2 2018.11.19 introducepondslider and separate thisPyPi package.
• 2.0.0 2019.01.18 Add Calibration, ABC on/off requested bythis issue. Please refer thiswiki.
• 0.3.5 2019.01.22 Both Python2 & Python3 support
• 2.3.6 2019.01.22 MergePull Request #3 &Pull Request #4. ThanksDavid!
• 2.3.7 2019.02.25 Add--all option which requested asissue#5, thanksRafał!
• 2.3.8 2019.04.16 MergePull Request #7. ThanksAlexander!
• 2.3.8.1 2019.04.20 MergePull Request #8. ThanksWO15!
• 2.3.8.5 2019.04.21 MergePull Request #9. ThanksWO15!
• 2.3.8.6 2019.04.22 MergePull Request #10. ThanksWO15!
• 2.3.9 2019.05.06 Revise the serial port selection logic. Support usingPL011 uart on Raspberry PiModel 3 and Zero W which is selected by setting dtoverlay=pi3-miniuart-bt or dtoverlay=pi3-disable-bt. Thanks片岡さん for your kindlyreport including this issue!
• 2.4.1 2019.08.11 Add --serial_device option as solution ofissue#12. ThanksActpohomoc andTBR-BRD!
• 2.4.2 2019.12.12 MergePull Request #15. ThanksWO15!
• 2.5.1 2020.05.16 Add--serial_console_untouched option to supportexecution without sudo asked asissue#17. Thanksralphbe91!
• 2.5.2 2020.06.30 Update the link for datasheet of MH-Z19B from version 1.0 to version 1.5 based be pointed it out asissue#18. ThanksWO15!
• 2.6.1 2020.07.07 Add--detection_range_10000 option to supportSet 0~10000ppm detection range asked asissue#19. ThanksWO15!
• 2.6.3 2020.08.27 Fixissue#21. Thanksidegre!
• 3.0.0 2021.02.05PWM support.
• 3.0.1 2021.02.17 Fix a degradation of not running with python3. Thank youMasahiko OHKUBO san for your report.
• 3.0.2 2021.03.25 Fix to support RPi4 correctly asissue#29. Thanksiperniaf!
• 3.0.3 2021.11.08 Fixissue#35. Thanksfalse!
• 3.0.4 2011.11.11 Fixissue#36. ThanksDavid Bock
• 3.0.5 2022.01.01 Fixissue#38. Thankskzehnter!
• 3.1.0 2022.01.22 add--co2valueonly option by mergingissue#39 andissue#40. Thanksjonesthefox!
• 3.1.1 2022.01.23 remove code clone.
• 3.1.2 2022.01.31 Fixissue#41. ThanksChristopher M. Pierce!
• 3.1.3 2022.02.25 Fixissue#43. ThanksJannis Möller!
• 3.1.4 2023.11.14 Don't install python2-pip if OS version is BullsEye or later.
• 3.1.5 2024.05.06 FIxissue#53. ThanksTats Shibata
• 3.1.6 2024.08.29 FIxissue#54. Thanks80kpc
• 3.1.7 2025.03.01 drop the RPi.GPIO dependenc. Thanksmroelandts