Indoor measuring of Co2 and Temperature
Especially in office environments employees are sensitive to high levels of Co2 and/or uncomfortably with hot office temperatures. This project consists of two parts, the monitor.py and the webinterface.
- monitor.py to read the data from TFA-Dostmann sensors and generating the graphs
- webinterface to display the graphs
Example Screenshot
-
Multiple CO2 Sensors are supported:
- TFA-Dostmann AirControl Mini CO2 Messgerät -- 65 euro (sends encrypted data)
- TFA-Dostmann AIRCO2NTROL Coach CO2 Monitor -- 72 euro (sends unencrypted data)
-
Raspberry PI 2 Model B -- 40 euro
-
case, 5v power supply, microSD card
Download Raspbian and install it on the microSD.
- Boot the raspberry with the raspbian and configure according to your needs.
At the moment, monitor.py renders the graphs to /var/www/html/images, and creates the RRD database in /var/local/monitor/co2-temp.rrd.
To change this, change the variables RRDDB_LOC and GRAPHOUT_DIR in monitor.py.
monitor.py should not run as root, so we create a service user (the group for this user is created automatically by adduser):
sudo adduser --home /var/local/monitor --shell /usr/sbin/nologin --disabled-password monitor
- install software
Other than Wooga this setup generates and serves the graphs locally, thus the following components are needed:
sudo apt-get install rrdtool python-rrdtool nginx ntp
cp /usr/share/zoneinfo/Europe/Vienna /etc/localtime
systemctl enable nginx
systemctl start nginx
systemctl enable ntp
systemctl start ntp
Copy monitor.py and the webinterface to their location:
sudo cp monitor.py /usr/bin
sudo mv /var/www/html/index.html /var/www/html/index.nginx-debian.html
sudo rsync -av --progress web/* /var/www/html
sudo mkdir /var/www/html/images
sudo chown -R monitor: /var/www/html/images
- fix socket permissions
The python script reading the sensor should not run as root, so the device permissions need to be set accordingly.
For a non-permanent fix run as root:
sudo chmod a+rw /dev/hidraw0
The better way to deal with this situation is to set the permissions using udev rules.
We want to set only the really needed permissions on the device, therefor the udev-rule should only apply to the specific device, or product which is announced by the device when USB initializes it.
To get the product name the bus and device id from lsusb is needed:
lsusb
Bus 001 Device 004: ID 04d9:a052 Holtek Semiconductor, Inc.
With this information the product name can be read from udevadm, using the bus id 001 and the device id 004 like this:
udevadm info -a -p $(udevadm info -q path -n /dev/bus/usb/001/004) | grep product
ATTR{product}=="USB-zyTemp"
The product name is in this case USB-zyTemp which can be used in the udev rule:
echo 'ACTION=="add", SUBSYSTEMS=="usb", ATTRS{product}=="USB-zyTemp", MODE="0664", GROUP="monitor"' > /etc/udev/rules.d/40-hidrwaw.rules
After plugging the TFA device in, at least one device file (e.g. /dev/hidraw0) should be generated with the correct permissions.
- run the script
monitor.py can be tested by invoking:
sudo -u monitor monitor.py /dev/hidraw0
We need to run it as monitor user because by default RRD databse is located in the folder where only monitor user has access to and access to a socket was granted to monitor group.
- run on startup
monitor.py can safely be called via a cronjob; it will exit if another instance is already running.
The cronjob can be added to /etc/crontab like this:
*/3 * * * * monitor /usr/bin/monitor.py /dev/hidraw0
- configure RRD database location and graph directory
- mobile webinterface navigation
- configuring webinterface strings
- notification via email
based on Wooga Office Weather