I have used already built-in serial connection for RFID reader. Is there way to use USB serial device to get information from CO2 sensor?
Or implement software serial like we have it on Arduino.

It was in mh_z19.service

Dear Sir

I am trying to read out CO2 values by running a python script with no success.
I have successfully been able to read CO2 values using this command from terminal:
sudo python -m mh_z19
And by opening python within the terminal and running the two lines:
import mh_z19
mh_z19.read()

If I make a script with the two lines of code mentioned and run it in terminal ore IDE, however, I am not able to read out CO2 values by get the following error message:

Could you help me figure out what I am doing wrong?

Hi,

is it possible to the humidity and the temperature with your library to increase the measurement accuracy and get a better Co2 result?

Currently there are 2 detection ranges you can select/set 2000ppm and 5000ppm see
https://github.com/UedaTakeyuki/mh-z19/wiki/CALIBRATION-&-detection-range
in the datasheet v1.5 in chapter 5 on page 5 there are 3 ranges indicated 2000, 5000 and 10.000.
Would it be possible to add the 10.000ppm range as a "detection_range_10000()" command to the code?
on page 8 of the datasheet the details are given.
Set 0~10000ppm detection range, send command: FF 01 99 00 00 00 27 10 2F

Hi,
I've cloned the most recent repo version and connected everything as shown in the Readme. However, it seems no value is received. This is my output and my connections:

sudo python -m mh_z19
{}

Hola a todos. Tengo una duda:

Si escribo en idle python3:

import mh_z19
mh_z19.abc_off()

¿Se desactiva el autocalibrado del sensor?

Muchas gracias por su gran trabajo.

PLEASE DON'T FORGET TO "STAR" THIS REPOSITORY :)

If you rather keep your project secret, feel free
to email the author at <[email protected]>; any
private correspondence is treated as confidential.
pi@raspberrypi:~ $ sudo python -m pondslider --config config.save.toml
Traceback (most recent call last):
File "/usr/lib/python3.9/runpy.py", line 197, in _run_module_as_main
return _run_code(code, main_globals, None,
File "/usr/lib/python3.9/runpy.py", line 87, in _run_code
exec(code, run_globals)
File "/usr/local/lib/python3.9/dist-packages/pondslider/main.py", line 6, in
import init as pondslider
ModuleNotFoundError: No module named 'init'

in README.md file and in the section about CALIBRATION you have several links to the datasheet available on the sensor manufacture website. This datasheet you currently link to is version 1.0 published in 2016, however there is also a version 1.5 published in 2019. Probably it is wise to link to this later version or if the old version is still relevant link to both.
link to version 1.5 on Winsen-sensor website.
https://www.winsen-sensor.com/d/files/MH-Z19B.pdf

Hallo,
I'm very new to all of this, so sorry in advance.

-Raspberry Pi 4 /w MH_Z19C
-I installed it via "pip install".
-I've enabled the serial port hardware in raspi-config as well as I2C which I need for the other part of my project.
-I triple-checked the wiring.
-The red led is blinking.
-I used "chmod 777" (just in case) for both /dev/ttyS0 and /dev/AMA0
-I disabled bluetooth just like one person of the other issues stated that it worked for them.
-After I used mh_z19.read_all() once, it reset all the permissions for ttyS0 back to what it was before. Therefore I get this after using it again:

Help? ^^°

Hallo Mr. Takeyuki and everyone,

I still have a problem with my MH-Z19C sensor, it is still always treturn {}, can someone help me? is it compatible for the MH-Z19C or only for B? I already read many blogs and github and I cannot solve my problem

I did my work on Raspberry Pi 5, and I also tried it on my 3+ but still not working. I already tried the pull-up resistor both for RX or TX pins.

Thank you so much.

On my Raspberry 3B+ I get
None from mh_z19.read() and 9 from mhz_19.read_all()
I am using Python3.6
The serial is /dev/serial1 -> ttyAMA0
The mh_z19 is connected RxD <-> TxD and TxD <-> RxD (physical pins 8 and 10)

There is also another module (SDS011) connected to USB.

Any suggestion for debugging?

Hi all,

I have an Mh-z19c connected to a Pi Zero W with TxD and RxD cross connected to pins 8 (GPIO 14) and 10 (GPIO 15) as per the repo readme and I see an orange light flashing inside indicating power.

The problem is the output from mh_z19 always {}.

I found the serial output is not passing this check:

if len(s) >= 4 and s[0] == 0xff and s[1] == 0x86 and ord(checksum(s[1:-1])) == s[-1]:
  return s[2]*256 + s[3]

Instead I see values like these examples:

ser.read(9): b'BM\x0c\x9c\t\xad\x02\x13\x01' - s[0]=66, s[1]=77, s[-1]=1
ser.read(9): b'(\x00\x00\xe2\x00\x06\x13BM' - s[0]=40, s[1]=0, s[-1]=77
ser.read(9): b'\x0c\x9c\t\xad\x02\x13\x01(\x00' - s[0]=12, s[1]=156, s[-1]=0
ser.read(9): b'\x00\xe2\x00\x06\x13BM\x0c\x9c' - s[0]=0, s[1]=226, s[-1]=156
ser.read(9): b'\t\xad\x02\x13\x01(\x00\x00\xe2' - s[0]=9, s[1]=173, s[-1]=226
ser.read(9): b'BM\x0c\x9c\t\xb2\x02\x15\x01' - s[0]=66, s[1]=77, s[-1]=1
ser.read(9): b'(\x00\x00\xe2\x00\x06\x1aBM' - s[0]=40, s[1]=0, s[-1]=77
ser.read(9): b'\x0c\x9c\t\xb2\x02\x15\x01(\x00' - s[0]=12, s[1]=156, s[-1]=0
ser.read(9): b'\x00\xe2\x00\x06\x1aBM\x0c\x9a' - s[0]=0, s[1]=226, s[-1]=154
ser.read(9): b'\t\xaa\x02\x15\x01(\x00\x00\xe2' - s[0]=9, s[1]=170, s[-1]=226

I've followed the advice of all the existing issues I can find:

• Enable serial port via raspi-config
• Ensure enable_uart=1 is in /boot/config.txt
• Set core_freq=250 in /boot/config.txt
• Set dtoverlay=disable-bt in /boot/config.txt to disable Bluetooth
• Add a resistor between TxD and Vin (I used a 2k)

If anyone has any suggestions they would be highly appreicated!

This is the variant of sensor I have:

Module documentation page has small typo, it has 'xero_point_calibration' as a function name while it should be 'zero_point_calibration'.

I was attempting to follow the instructions at https://github.com/UedaTakeyuki/mh-z19/wiki/How-to-Enable-Serial-Port-hardware-on-the-Raspberry-Pi but ran into issues with permissions on the /dev/ttyS0 port on (rpi3). I added the enable_uart=1 in /boot/config.txt and rebooted, the device was set with permissions 620. I could chmod them but it would reset on boot.

The only way I found to fix this issue was to use the raspi-config instructions instead. Is this the intended behavior?

It would be better to not run python as root or with sudo as it wreaks havoc with pipenv and dependencies. I think that by enabling the serial port via raspi-config the resultant permissions should let me run python as a normal user and still access the hardware.

As requested on https://github.com/UedaTakeyuki/mh-z19/blob/master/pypi/README.md, I'd like to report that the zero point calibration function seems to be working as expected. When called e.g. by

sudo python -m mh_z19 --zero_point_calibration

the current CO2 concentration is set to represent 400 ppm CO2. This was checked in the following way:

1. calling
   sudo python -m mh_z19 --all
   showed a reading of more than 800 ppm.
2. calling
   sudo python -m mh_z19 --zero_point_calibration
   returned a message saying that ZERO point calibration was carried out.
3. immediately thereafter, without changing, calling again:
   sudo python -m mh_z19 --all
   returned a reading close to 400 ppm.

Tested using a mh_z19b device connected to a Raspberry Pi Zero W, purchased in the fall of 2020.

As my project does not use json, i wanted the module just to return a raw number. so I added an 'co2valueonly' option to it.

I'll try to add an pull request :)

pip install mh-z19 fails if the packages setuptools and wheel are not installed.

on https://github.com/UedaTakeyuki/mh-z19/wiki/CALIBRATION-&-detection-range you refer to xero_point_calibration() assume this should be zero_point_calibration()

Thanks for this usefull package and the clear documentation! The installation went well on a RPI 3B and I got sensor readings. I want to use the sensor in Python programs and so I want to get rid of the root permission. Unfortunately this doesn't work for me.
I used sudo chmod g+r /dev/ttyAMA0
using ls -la /dev/ttyAMA0 this gave me crw-rw---- 1 root tty 204, 64 Nov 8 20:00 /dev/ttyAMA0
but when I tried python3 -m mh_z19 --serial_console_untouched I got an error:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/serial/serialposix.py", line 265, in open
    self.fd = os.open(self.portstr, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
PermissionError: [Errno 13] Permission denied: '/dev/serial0'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/pi/mh-z19/mh_z19.py", line 66, in read_concentration
    ser = connect_serial()
  File "/home/pi/mh-z19/mh_z19.py", line 62, in connect_serial
    timeout=1.0)
  File "/usr/lib/python3/dist-packages/serial/serialutil.py", line 240, in __init__
    self.open()
  File "/usr/lib/python3/dist-packages/serial/serialposix.py", line 268, in open
    raise SerialException(msg.errno, "could not open port {}: {}".format(self._port, msg))
serial.serialutil.SerialException: [Errno 13] could not open port /dev/serial0: [Errno 13] Permission denied: '/dev/serial0'
{}

And then the 'r' on the fifth position is gone and I have to use chmod again. How to solve this?

Hi everybody,

I am currently trying to get some data using the mh-z19. Considering installation and connection, everything works perfectly fine for me. However when I started to track the data (I am writing it into a .csv file), I would always get the same value for temperature and almost the same values for the co2 measuring:

CO2,Temperature,Time
400,3,31/03/2022 21:00:55
400,3,31/03/2022 21:01:10
400,3,31/03/2022 21:01:25
400,3,31/03/2022 21:01:40
400,3,31/03/2022 21:01:55
400,3,31/03/2022 21:02:10
400,3,31/03/2022 21:02:26
400,3,31/03/2022 21:02:41
400,3,31/03/2022 21:02:56
448,3,31/03/2022 21:04:45
446,3,31/03/2022 21:05:00
442,3,31/03/2022 21:05:15
437,3,31/03/2022 21:05:30
438,3,31/03/2022 21:05:46
434,3,31/03/2022 21:06:01
430,3,31/03/2022 21:06:16
432,3,31/03/2022 21:06:31
436,3,31/03/2022 21:06:46
437,3,31/03/2022 21:07:01
439,3,31/03/2022 21:07:17
435,3,31/03/2022 21:07:32
433,3,31/03/2022 21:07:47
438,3,31/03/2022 21:08:02
444,3,31/03/2022 21:08:17
448,3,31/03/2022 21:08:33
448,3,31/03/2022 21:08:48

Some information about the environment: the sensor is currently placed inside where the temperature is at 18-20 degrees celsius.
Additionally I spent a lot of time in the room the sensor is placed in and I didn't open the windows . So I am sure that the co2 concentration is wrong, same goes for the temperature.

I was thinking that the sensor maybe needs some time to calibrate itself but after running 24 hours and giving me more than 5000 entries with always the same temperature of 3 degrees and nearly always the same co2 value (between 400-500ppm), I don't think its working properly.

Maybe you can help me and know how to fix this Issue or somehow 'calibrate' the sensor again, I am really clueless at the moment.

I would be very grateful if you can help me.

I have a python program which calls mh_z19.read() every few seconds and sometimes (I don't know why it is only sometimes) I get this error:

Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/mh_z19/init.py", line 73, in mh_z19
if len(s) >= 4 and s[0] == "\xff" and s[1] == "\x86" and checksum(s[1:-1]) == s[-1]:
File "/usr/local/lib/python2.7/dist-packages/mh_z19/init.py", line 231, in checksum
return struct.pack('B', 0xff - (sum(array) % 0x100) + 1)
error: ubyte format requires 0 <= number <= 255

Steps to reproduce:
Call mh_z19.read() every 2 seconds and wait.
In an hour of runtime it happened around 4 times.

Is it possible to use this library with Python 3 without sudo?

When I use "import mh_z19" and "mh_z19.read()" in my program it doesn't work. Although I have activated the serial port (just as you and others decribed ist), I get the following error: PermissionError: [Errno 13] Permission denied: '/dev/serial0'. The sensor is working, because when I use "$ sudo python -m mh_z19" I get the desired result.

I am a beginner in Python, that has already taken up a lot of my time.

Hi,
I'm using your lib with a rpbi 4 and it needs some fixes.
¿Can I contribute to the community fixing them?

I am using MH_Z19B with a Raspberry Pi 3B
I always get null when I use sudo python -m mh_z19
I activated Serial in raspi-config
I wired everything correct but I can't find the problem.
When the sensor is not connected it also shows null
Could you please help me find the problem ?

I have the MH-Z19 attached to the ANAVI phat, on a raspberry pi zero w. I installed the python modules and enabled the i2c interface. I found a similar help request, but I tried all of the different codes and nothing happened.

THis is my wiring:
Tx-Rx
Rx-Tx
vin-3.3v
GND-GND
When I type insudo python -m mh_z19 this output is null.

when attempting to use the --serial_device parameter it always returns an error.
sorry I don't have the exact error as I changed the code on my pi and didn't get any screenshots or the exact error. I found this when trying to use a usb->serial interface on my pi3 so i wouldn't need to deal with the onboard serial
luckily its an easy fix, but i cant create a PR to save you the trouble
https://github.com/UedaTakeyuki/mh-z19/blob/master/pypi/mh_z19/__main__.py#L56 here it should be mh_z19.set_serialdevice(args.serial_device)

Describe the bug
when attempting to use the --serial_device parameter it always returns an error.
sorry I don't have the exact error as I changed the code on my pi and didn't get any screenshots

To Reproduce

1. call sudo python3 -m mh_z19 --serial_device /dev/ttyUSB0
2. see set_serialdevice(args.serial_device) is undefined error

Expected behavior
the command should work

Screenshots
If applicable, add screenshots to help explain your problem.

Hi! Like your work on the mh-z19. It works flawless when using as command line (python -m mh_z19) and by downloading the file. I want to use your code with a program i have wrote on python3 (it performs different actions depending on the co2 value) but I always have problems with the import. After solving some of them (as using .encode() ) i cant move foward after this message:

Traceback (most recent call last):
  File "/home/pi/Desktop/soul/mh_z19-0.1.6/mh_z19/__init__.py", line 73, in mh_z19
    s=ser.read(9)
  File "/usr/lib/python3/dist-packages/serial/serialposix.py", line 497, in read
    raise SerialException('read failed: {}'.format(e))
serial.serialutil.SerialException: read failed: device reports readiness to read but returned no data (device disconnected or multiple access on port?)

I think this happens because the file is being imported (import init as mh_z19) from a python3 file.
What can you suggest me?

mh_z19 3.1.3 doesn’t work with Raspberry Pi 5 because the dependent RPi.GPIO 0.7.1 doesn’t work with it.

It seems RPi.GPIO is no longer maintained because of no response to the ticket to support RP5. The official RP doc is using gpiozero to access GPIO.

$ python3 -m mh_z19 --pwm
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/var/lib/python/ansible/lib/python3.12/site-packages/mh_z19/__main__.py", line 104, in <module>
    print (mh_z19.read_from_pwm(gpio=args.pwm_gpio, range=args.pwm_range))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/lib/python/ansible/lib/python3.12/site-packages/mh_z19/__init__.py", line 222, in read_from_pwm
    GPIO.setup(gpio,GPIO.IN)
RuntimeError: Cannot determine SOC peripheral base address

According to this webpage https://revspace.nl/MHZ19 it should be possible (although not documented in official datasheet) to read the temperature along with CO2 level. Would it be possible to include this information in the result?

Hi, I ran the following command as written in the readme
git clone https://github.com/UedaTakeyuki/mh-z19.git
. /setup.sh
but when I do sudo python -m mh_z19, I get No such file or directory: ' /dev/ttyS0't
I enabled serial communication in raspi-config and did sudo python -m mh_z19, but it shows {}.
I also tried PWM but it timed out and could not get the value.

Describe the bug
Thanks for the library! I have an issue where pip fails to install it on Windows due to character encoding in README.md read by setup.py. By the way, my use case is that I am developing code on a Windows platform and then pushing it to a Raspberry Pi to take advantage of my existing IDE setup.

Here is a full copy of the pip error:

Collecting mh-z19
  Using cached mh_z19-3.1.1.tar.gz (13 kB)
  Preparing metadata (setup.py): started
  Preparing metadata (setup.py): finished with status 'error'

  error: subprocess-exited-with-error
  
  python setup.py egg_info did not run successfully.
  exit code: 1
  
  [8 lines of output]
  Traceback (most recent call last):
    File "<string>", line 2, in <module>
    File "<pip-setuptools-caller>", line 34, in <module>
    File "C:\Users\Christopher Pierce\AppData\Local\Temp\pip-install-n1zxmenn\mh-z19_8fc0a2b6efaf4a988424c84193cf061c\setup.py", line 4, in <module>
      long_description = f.read()
    File "C:\Users\Christopher Pierce\AppData\Local\Programs\Python\Python39\lib\encodings\cp1252.py", line 23, in decode
      return codecs.charmap_decode(input,self.errors,decoding_table)[0]
  UnicodeDecodeError: 'charmap' codec can't decode byte 0x81 in position 10805: character maps to <undefined>
  [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

Encountered error while generating package metadata.

See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

To Reproduce
Steps to reproduce the behavior:

1. Create a new venv on a Windows computer
2. Run pip3 install mh_z19

Expected behavior
The library is installed.

Hi there,

first of all thank you for your package. I have recently started playing around with a rpi 4 and wanted to connect a mh-z19b with your python package.

I made sure the serials are available:

serial0 -> ttyS0
serial1 -> ttyAMA0

Enabled i2c
However i2c output is empty

And even made sure uart is enabled (as seen on another blog )

When I run sudo python -m mh_z19 I (most of the time) get back
null

Sometimes, however there is also another message:

Here is my cabling set up.

I should mention, that the soldered pins at the mh-z19b where bent a bit due to delivery. But I don't think (hope) this is a problem.

Do you have any ideas what else I could test to make it work?

Thanks in advance!

Hello everyone, I come to comment on a positive and a negative result. I have raspberry pi 3 b +.
I have tested the abc_off () function for 7 days continuously and it works fine. On the other hand, when I print(mh_z19.read_from_pwm ()) everything goes well and I get the correct reading, but when I print (mh_z19.read()) I get an error. I attach an image with the error that I get. I have previously made the configuration included in this link but I keep getting the error of the attached image. Somebody could help me?

Thank you

Hey,

I received my MH-Z19B and connected it to my raspberry.

I ran a pip install mh-z19 and when I execute python -m mh_z19 --all I receive the following output:
{"SS": 0, "UhUl": 0, "TT": 50, "co2": 5000, "temperature": 10}

Temperature is reported more or less correctly (compared against thermometer and DHT22). But co2 value can't be correct. Point of measure was outside.

What else can I do for debugging?

There are several other features available on the sensors as per the datasheets for MH-Z19, MH-Z19B.

I have an MH-Z19B and noticed it has automatic baseline correction which resets the reading to 400ppm. This has been brought up in other projects

Support for calibration (zero point and span)

Although not documented, apparently can read temperature [1][2]

Hello, I'm a newbie to python and it's packages so i blindly followed your instructions to install and use your module from https://pypi.org/project/mh-z19/
I'm connected to my Raspberry over SSH.
Taking the pip install route, which is the easiest but python not finding the module (error in title) led me to try to run it with python3 and even reinstalling it with pip3 left me with no error but also with no success.

So, there are two things I noticed while inspecting the instructions:

Install:
pip install mh-z19

Use:
sudo python -m mh_z19

1. the use of sudo
2. the use of - and _

What I've did now was like:

Install:
sudo pip install mh_z19

Use:
sudo python -m mh_z19

And it works.
Seems like it makes no difference if using - or _ for install but the sudo made a difference.
Am I right that something's not proper with that instructions?

PLEASE DON'T FORGET TO "STAR" THIS REPOSITORY :)

If you rather keep your project secret, feel free
to email the author at <[email protected]>; any
private correspondence is treated as confidential.

When reporting a bug please include the following:

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
If applicable, add screenshots to help explain your problem.

Hi Takeyuki,
I found that when using Raspberry Pi 5, it is necessary to specify the serial device. Is this expected behavior?

When I connect the MH-Z19E to the Raspberry Pi 5 according to the wiring instructions in the README and run the command
sudo python3 -m mh_z19
the output is
{}

However, when I specify the serial device in this command
sudo python3 -m mh_z19 --serial_device /dev/ttyAMA0
I get an output like
{"co2": 1711}

This might be related to a change in the Raspberry Pi 5.
https://www.raspberrypi.com/documentation/computers/configuration.html#primary-and-secondary-uart

/dev/serial0 and /dev/serial1 are symbolic links which point to either /dev/ttyS0 or /dev/ttyAMA0.
On the Raspberry Pi 5, /dev/serial0 is a symbolic link that points to /dev/ttyAMA10.

mh_z19 Version: 3.1.5
Device: MH-Z19E

Hi,

I have the mh-z19b. I have installed the library but I am not getting data.

I also tried in a python file with

import mh_z19
mh_z19.read()

I get none back with that.