George Smart - M1GEO

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Air Particulate Sensor

Posted: 29 Feb 2020 02:18 PM PST
https://www.george-smart.co.uk/2020/...culate-sensor/


Background




Around a year ago a colleague mentioned to me the Luftdaten project (en:
air data project). It is a sort of citizen science project which measures
and records particulate matter in the air. They also have a newer project
concerning acoustic noise levels (build notes for this in German here), but
Ill be concentrating on particulate matter here. Often the sensors are
combined to collect data on airborne particulate levels, acoustic noise,
temperature, humidity and air pressure to name a few. The images below show
24h graphs for some of the measured parameters from various sensors around
Europe.



Air pressureTemperatureAcoustic noiseParticulate matter




I have long had a fondness for collecting data and the Luftdaten project
has plenty! Their website features an interactive map of the world where
they plot measurements taken.








The particulates detected include dust, dirt, soot, smoke, and liquid
droplets emitted into the air which are small enough to be suspended in the
atmosphere. Airborne particulates may be a complex mixture of organic and
inorganic substances. The type of sensor used does not differentiate
between the particle types, it just gives a measure of how many are present.



Parts




I purchased all of the parts cheaply from AliExpress (no affiliation).
Youll find the same parts on eBay, BangGood, etc., so use what you prefer.








The particulate matter sensor is a Nova SDS011 PM sensor (datasheet), which
can be purchased for around £14.








Youll probably also want a DHT22 temperature & humidity sensor (datasheet)
which will cost around £2.




Finally a NodeMCU V3 is required. This is a module based on the ESP8622
WiFi chip, which includes a USB-UART interface, some voltage regulators,
etc. In a later step, well program this with the Luftdaten code.








A short length of plastic pipe can help to draw air into the SDS011 sensor.
The datasheet for the SDS011 suggests an inside diameter of 6mm and outside
diameter of 8mm.








The photo below shows my assembled parts! Youll notice int he bottom right
of the image that I have an Influencair V1.2 PCB. Influencair are a
spin-off group of Luftdaten based in Belgium. CivicLabsBelgium produced
PCBs for project participants to use and made the PCB Gerber Files
available here. You can send these off for manufacture using any PCB
service you like (for example, in no order JLCPCB, PCBWay, DirtyPCBs,
Elecrow, and so on).







Build notes & Programming




The build process is explained thoroughly on the Luftdaten website under
the construction manual page. As I wont be able to do a better job of
explaining this, I suggest you go ahead and read their documentation.
Below shows the parts mounted on my Influencair V1.2 PCB. I used 3mm screws
to hold everything together.







Programming, Configuration & Registering




The default programming proceedure requires setting up the ESP8622 in the
Arduino software environment, but Piotr Dobrowolski has created a very
useful tool: airrohr-firmware-flasher for the Luftdaten project. I used the
Linux variant of the program the NodeMCU in one click, but Windows and
macOS versions exist too! Be sure to find the releases button on GitHub to
download the pre-compiled ready-to-use binaries!




With the NodeMCU connected to the PC with a USB cable, I selected
latest_en.bin from the version list (en being English), and pressed Upload.
As you can see from the figure below, it took just over 8 seconds and it
was done!








Power cycling the board resulted in a WiFi device being created by the
newly created sensor! I connected my mobile phone to airRohr-11189671 and
was greeted with the following screen.








I tapped on my house WiFi SmartLAN, entered my super-secret passkey and we
were away! The device power cycled and was then visible from the flasher
once again.








From this, I was able to see the sensor was assigned an IP address on my
network, and double-clicking on the entry whisked me off to my default web
browser viewing the sensors internal webpages.








There are many configuration options, but the defaults were suitable for my
hardware configuration. There are options for OLED and LCD screens,
extra/different sensors and many other configurations which are out of the
scope of this article. However you can click Current Data to see the
sensors latest measurement data. The image below was taken with the sensor
indoors.












The final thing to do is to create an account on the Luftdaten project
website so your sensor can contribute measurements. There are already a
reasonable number of sensors in the UK contributing data to Luftdaten. You
can create your account and submit your sensor data he
https://meine.luftdaten.info




I have positioned my sensor in the garden shed with a short section of
plastic pipe poking outside of the shed where the wind blows. I live near a
busy roundabout and buy a petrol filling station, so it will be interesting
to compare my measurements with other local sensor readings.