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UedaTakeyuki / mh-z19

Read CO2 concentration from mh-z19 sensor on the Raspberry Pi & handle it. Detect Raspberry Pi model automatically and read the value from an appropriate serial device.
MIT License
185 stars 37 forks source link

Returns null - Need help #26

Closed OlafKocanda closed 3 years ago

OlafKocanda commented 3 years ago

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: IMG_1122

Here is my cabling set up. IMG_0623

IMG_0625

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!

nincube8 commented 3 years ago

You need a 1-5k Ohm resistor between Vcc+ and TxD line.

On Sun, Dec 13, 2020 at 7:33 AM Olaf Kocanda notifications@github.com wrote:

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 https://www.circuits.dk/testing-mh-z19-ndir-co2-sensor-module/ )

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

Sometimes, however there is also another message: [image: IMG_1122] https://user-images.githubusercontent.com/58265203/102014806-2f01de00-3d58-11eb-9cfc-5378564dfbaa.jpg

Here is my cabling set up. [image: IMG_0623] https://user-images.githubusercontent.com/58265203/102014588-ff9ea180-3d56-11eb-8034-541b22045080.jpg

[image: IMG_0625] https://user-images.githubusercontent.com/58265203/102014605-1ba24300-3d57-11eb-8d48-4d6b02994e1a.jpg

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!

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OlafKocanda commented 3 years ago

Hi nincube8,

Thanks a lot for your answer! Could you explain a bit what you mean by Vcc+ and TxD line?

Do you want me to put a resistor going from the Vin to the Tx on the MH-Z19B? 102014605-1ba24300-3d57-11eb-8d48-4d6b02994e1a

nincube8 commented 3 years ago

You should be able to see the unit light up through the white box on the side. Usually it's the transfer packet clock that needs a resistor (Tx = Transfer) between the (Vcc 3v) to be able to decode the strings received by the unit correctly. The (RxD = Receive line) doesn't need the resistor.

On Mon, Dec 14, 2020 at 1:29 AM Olaf Kocanda notifications@github.com wrote:

Hi nincube8,

could you explain a bit what you mean by Vcc+ and TxD line?

Do you want me to put a resistor going from the Vin to the Tx on the MH-Z19B? [image: 102014605-1ba24300-3d57-11eb-8d48-4d6b02994e1a] https://user-images.githubusercontent.com/58265203/102057757-b39f3b80-3dee-11eb-96dd-8be0933ce8c2.jpg

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/UedaTakeyuki/mh-z19/issues/26#issuecomment-744271089, or unsubscribe https://github.com/notifications/unsubscribe-auth/AEBLRRJTPYCLRW7CJZBTVDLSUXEGDANCNFSM4UZRETAA .

nincube8 commented 3 years ago

I believe this unit is a 5 Volt unit and requires the 5 volt rail on your Device or Microcomputer.

On Mon, Dec 14, 2020 at 1:41 AM CK Gaming Channel cevatkose@gmail.com wrote:

You should be able to see the unit light up through the white box on the side. Usually it's the transfer packet clock that needs a resistor (Tx = Transfer) between the (Vcc 3v) to be able to decode the strings received by the unit correctly. The (RxD = Receive line) doesn't need the resistor.

On Mon, Dec 14, 2020 at 1:29 AM Olaf Kocanda notifications@github.com wrote:

Hi nincube8,

could you explain a bit what you mean by Vcc+ and TxD line?

Do you want me to put a resistor going from the Vin to the Tx on the MH-Z19B? [image: 102014605-1ba24300-3d57-11eb-8d48-4d6b02994e1a] https://user-images.githubusercontent.com/58265203/102057757-b39f3b80-3dee-11eb-96dd-8be0933ce8c2.jpg

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/UedaTakeyuki/mh-z19/issues/26#issuecomment-744271089, or unsubscribe https://github.com/notifications/unsubscribe-auth/AEBLRRJTPYCLRW7CJZBTVDLSUXEGDANCNFSM4UZRETAA .

OlafKocanda commented 3 years ago

just to make sure: The MH-Z19B is connected to the 5v pin on my raspberry.

Shouldn't the light be on if it receives enough power without any further resistors?

nincube8 commented 3 years ago

Yes, that is correct.

On Mon, Dec 14, 2020 at 1:52 AM Olaf Kocanda notifications@github.com wrote:

just to make sure: The MH-Z19B is connected to the 5v pin on my raspberry.

Shouldn't the light be on if it receives enough power without any further resistors?

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/UedaTakeyuki/mh-z19/issues/26#issuecomment-744284805, or unsubscribe https://github.com/notifications/unsubscribe-auth/AEBLRRPQHHGEOREQWQ6OE7DSUXG4LANCNFSM4UZRETAA .

OlafKocanda commented 3 years ago

Thanks!

Well, then I believe there is something else I am missing here to make it work...

DoudouHirofumi commented 3 years ago

Hi there. I had the same problem. Please try to install "i2c-tools". sudo apt install i2c-tools

After installing it, the "null" problem was solved.

mazdafunsunn commented 3 years ago

I have same problem. will try to solder. i2c-tools was already installed. red LED is blinking.

smrt28 commented 3 years ago

I had the same issue. I added:

[all]
enable_uart=1
core_freq=250

to /boot/config.txt, reboot and /dev/serial0 works.

mazdafunsunn commented 3 years ago

I had the same issue. I added:

[all]
enable_uart=1
core_freq=250

to /boot/config.txt, reboot and /dev/serial0 works.

This worked for me as well.

UedaTakeyuki commented 3 years ago

no feedback

flipper31 commented 3 years ago

I put a 1k Ohm resistor between Tx and Vin still Null then I Tried 3k Ohm but still null every other solution like fix core_freq to 250 are not working aswell. :/ Do you have any ideas to solve this problem ?

mohshbool commented 3 years ago

I put a 1k Ohm resistor between Tx and Vin still Null then I Tried 3k Ohm but still null every other solution like fix core_freq to 250 are not working aswell. :/ Do you have any ideas to solve this problem ?

im having the same problem as you man. pi 4b

UedaTakeyuki commented 3 years ago

How about using PWM interface?

https://github.com/UedaTakeyuki/mh-z19#pwm-support

mohshbool commented 3 years ago

How about using PWM interface?

https://github.com/UedaTakeyuki/mh-z19#pwm-support

i tried that man, i connected the pwm on the sensor to gpio12, gpio26 and gpio 16 (which is the fifth one from the top right) here's what gpio readall shows: 

 +-----+-----+---------+------+---+---Pi 4B--+---+------+---------+-----+-----+
 | 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      |     |     |
 |   3 |   9 |   SCL.1 |   IN | 1 |  5 || 6  |   |      | 0v      |     |     |
 |   4 |   7 | GPIO. 7 |   IN | 1 |  7 || 8  | 1 | ALT5 | TxD     | 15  | 14  |
 |     |     |      0v |      |   |  9 || 10 | 1 | ALT5 | RxD     | 16  | 15  |
 |  17 |   0 | GPIO. 0 |   IN | 0 | 11 || 12 | 0 | IN   | GPIO. 1 | 1   | 18  |
 |  27 |   2 | GPIO. 2 |   IN | 1 | 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 | 1 | 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 4B--+---+------+---------+-----+-----+

and here's the error im getting 

pi@raspberrypi:~ $ python -m mh_z19 --pwm --pwm_gpio 12 --pwm_range 2000
Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/home/pi/.local/lib/python2.7/site-packages/mh_z19/__main__.py", line 101, in <module>
    print mh_z19.read_from_pwm(gpio=args.pwm_gpio, range=args.pwm_range, )
  File "/home/pi/.local/lib/python2.7/site-packages/mh_z19/__init__.py", line 213, in read_from_pwm
    raise GPIO_Edge_Timeout("gpio {} edge timeout".format(gpio))
mh_z19.__init__.GPIO_Edge_Timeout: gpio 12 edge timeout
UedaTakeyuki commented 3 years ago

For PWM, connect with 3 lines: 5V, GND, and signal line(Fx: gpio12). refer https://github.com/UedaTakeyuki/mh-z19/wiki/PWM-support.#cabling