Moon Rabbit CO2 Sensor (Raspberry Pi, scd30, bme280, flask & python)

A Raspberry Pi powered CO2 monitoring station using Python and Flask
If starting with blank micro SD card:

Flash the Micro SD card with the Rapberry Pi Imager

Use settings: "Raspberry Pi Zero 2 W", "64 Bit",

MoonRabbit setup

Via a keyboard, mouse and screen through the rpi0 OTG port

Connect your keyboard and mouse to the OTG port via a OTG (On-The-Go) USB hub with a micro USB plug. Connect the monitor to the mini-HDMI port and boot by plugging the power cable in.

On first start, setup the default user name "pi" and password "RaspberryPi"

Connect to WiFi

Enable Raspberry Pi Connect if you like.

"Skip" OS Update

Restart

Set up WiFi or Network

If WiFi not yet connected: Connect to the WiFi using the icon at the top right of the screen.

Set up SSH & I2C

Menu>Preferences>Praspberry Pi Configuration>Interface>SSH

Menu>Preferences>Praspberry Pi Configuration>Interface>I2C

Menu>Preferences>Praspberry Pi Configuration>Interface>VNC

Menu>Preferences>Raspberry Pi Configuration>Localisation>Locale Menu>Preferences>Raspberry Pi Configuration>Localisation>Timezone Menu>Preferences>Raspberry Pi Configuration>Localisation>Keyboard if necessary Menu>Preferences>Raspberry Pi Configuration>Localisation>WiFi Country

Via SSH

You'll need the IP address of your raspberry pi. Get it from

(venv) pi@raspberrypi:~ $ ifconfig | grep 192
        inet 192.168.1.61  netmask 255.255.255.0  broadcast 192.168.1.255

And it's the address of the format 192.168, but not ending 255, so in this case its 192.168.1.61

Fix swap memory default

The initial default, virtual memory allocation is very small. You need to expand it to allow many things, such as updating software.

Run swapon command

swapon
> NAME      TYPE  SIZE   USED PRIO
> var/swap file 100M 100M   -2

Swap Memory is 100 MB

sudo nano /etc/dphys-swapfile

Change swap size to 1024 MB

CONF_SWAPSIZE=1024

Use Control-s to save the changes and control-x to exit nano. Then reboot Moon Rabbit, to apply the changes.

sudo reboot

Check swapsize again

swapon
> NAME      TYPE  SIZE   USED PRIO
> var/swap file 1024M 377.8M   -2

Swap size has changed

Supervisord

Supervisord allows remore control of the software on the Raspberry Pi Zero 2 W from a browser on the same WiFi LAN.

Install Supervisord

# Update and upgrade the system packages
sudo apt-get update && sudo apt-get upgrade -y
# Install necessary packages
sudo apt-get install -y supervisor

Edit Supervisor configuration to allow web interface

sudo nano /etc/supervisor/supervisord.conf Add the following lines to enable the web interface

[inet_http_server]
port=*:9001

Use Control-s to save the changes and control-x to exit nano.

Enable hardware interfaces in the Raspberry Pi configuration

IIC or I2C (I-squared-C, or I-two-C), is the interface that links all the sensors to the Raspberry Pi Zero 2 W

sudo nano /boot/firmware/config.txt

# Uncomment  or add these lines to enable the hardware interfaces

dtparam=i2c_arm=on
#dtparam=i2s=on
dtparam=spi=on

# Set I2C Clock Speed
dtparam=i2c_arm_baudrate=10000

Use Control-s to save the changes and control-x to exit nano.

Install Moon Rabbit Software

# Clone the project repository
git clone https://github.com/SteveBz/MoonRabbit
cd MoonRabbit/
# Set up Python virtual environment and activate it
python3 -m venv venv
. venv/bin/activate
sh install.sh

Test Moon Rabbit in a browser

Navigate to a browser, open two tabs and type in the following IP adresesses:

<your ip address>:5000
<your ip address>:9001

Eg, like this, substituting your address for the example.

192.168.1.61:5000
192.168.1.61:9001

MoonRabbit Calibration

Some of the SCD30s come nicely calibrated, some are well out. Of the two I just one was rught with about 6 ppm, and one was out by 150 ppm.

As we don't know which is which, we have to calibrate them all. This is a major cost item. A bottle of calibration gas and a valve just cost me £250 as of 2024. For this you can calibrate about 4 Moon Rabbits.

I bought a 2000 ppm cylinder of CO2 and air calibration gas.