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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
182 stars 37 forks source link

sudo python -m mh_z19 alway returns {} #49

Closed test597 closed 1 year ago

test597 commented 1 year ago

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.

test597 commented 1 year ago

I am using raspberry pi zero w. I also use USB to communicate with my PC via ssh to control the raspberry pi.

UedaTakeyuki commented 1 year ago

Hi test597,

The output {} means that your RPi can read/write a serial interface correctly but with no feedback. The possible cause is hardware problem. Fx: the cable problem, the sensor module problem, and so on. Or the serial port is not connected to the sensor module. I'm not familiar with USB OTG, but I'm afraid that doesn't it occupy the serial port.

For PWM, it just uses simple gpio, so a hardware matter is more suspicious.

test597 commented 1 year ago

Okay, I'm on the road now, so I'll try it without USB OTG when I get back.

test597 commented 1 year ago

I did not use USB OTG and it did not work well. When PWM was used, a very high value of 5100 ppm was displayed. I used --zero_point_calibration, but the result did not change.

UedaTakeyuki commented 1 year ago

I did not use USB OTG and it did not work well.

So, the most doubtable cause is Hardware, I recommend you make sure the cabling, sensor module and so.

Also, this article might help you. https://github.com/UedaTakeyuki/mh-z19#in-case-you-cant-get-the-value

When PWM was used, a very high value of 5100 ppm was displayed.

How did you measure with PWM? Did you mean measure with my library as follow?

python -m mh_z19 --pwm

If so, it's weird. The default range is 5000ppm, so it doesn't indicate over 5000. Also, calibration by --zero_point_calibration is no mean. It also depends on the Serial connection between MH_Z19 and RPi.

test597 commented 1 year ago

Sorry, it was incorrectly CLOSED.

The values measured by running python -m mh_z19 -pwm are running in 5ppm increments like 5100, 5095, and 5115. Values of 5115 and 5110 are relatively easy to output in a closed environment, and values of 5095 and 5100 in a ventilated environment.

UedaTakeyuki commented 1 year ago

I'm afraid I have no idea to help with this problem. Please fix your Hardware problem yourself. Bay bay.