2/7/2026 1 PM - Research on enviromental monitoring

I did a lot of research on enviromental monitoring.

I would like to measure metrics with which anyone can come into contact in everyday life.
I think that temperature and relative humidity are a baseline for comfort.
For office/home use I like CO2, PM2.5. These are all the basic ones which should suite almost everyone.

Ground level ozone seems like a great thing for an everyday node.
NO₂ and Formaldehyde are not super nessesary for everyday life but it's good to note traffic pollution and carcidogens. VOCs are good to measure but not strictly nesecery.
Then I started thinking about the UV index and sound polution, because smart citizen kits also measure these kinds of data. and it makes sense.

But I'm not a normal human.
I use paints, solvents, solder and other random stuff. So I also need VOCs and the other stuff. Also I would like to know how to mitigate the sources.

My references and sources are:
https://www.hackster.io/21cncstudio/project-aura-open-source-esp32-air-quality-monitor-8cb256
https://sensirion.com/products/catalog/particulate-matter-sensors
https://sensirion.com/products/catalog/SEN66
There is already an arduino library for it.
https://github.com/paulvha/SEN6X
https://github.com/Sensirion/arduino-i2c-sen66
https://meshtastic.org/docs/configuration/module/telemetry/
https://smartcitizen.me/
https://docs.smartcitizen.me/knowledge/
https://www.printables.com/model/1079858-3d-printer-emission-sensor-array-sensorbox-v2

I've made this table with chatgpt:

Metric	What it physically represents	What it’s good at telling you	Where it shines most	Best use case
PM1.0	Particles <1 µm (ultrafine dust, combustion aerosols)	Deep lung–penetrating pollution, often from combustion	Indoor & outdoor	Traffic pollution, wildfire smoke, health-focused monitoring
PM2.5	Fine particles <2.5 µm	The most health-relevant PM metric	Indoor & outdoor	Regulatory-style AQ monitoring, public health, smoke events
PM4.0	Medium-fine particles	Transitional dust fraction (less standardized)	Indoor	HVAC efficiency, filtration studies
PM10	Coarse particles <10 µm (dust, pollen, sand)	Mechanical dust and resuspended particles	Outdoor	Construction dust, agriculture, road dust
Temperature	Ambient air temperature	Context for sensor compensation and comfort	Indoor & outdoor	Thermal comfort, correcting PM/VOC readings
Relative Humidity (RH)	Water vapor content in air	Explains PM swelling and VOC sensor drift	Indoor & outdoor	Mold risk, PM correction, climate context
VOC index	Aggregate signal from volatile organic compounds	Human activity, off-gassing, indoor pollution trends	Indoor	Indoor air quality, occupancy/activity detection
NOx index	Nitrogen oxides (NO + NO₂ trend)	Combustion exhaust and traffic pollution	Outdoor & kitchens	Traffic exposure, gas stoves, combustion sources
CO₂	Carbon dioxide concentration	Ventilation effectiveness and occupancy	Indoor	Ventilation control, classrooms, offices
Particle count	Number of particles by size	Source identification and dynamics	Indoor & outdoor	Research, aerosol behavior, diagnostics

2/7/2026 2 PM - Deciding on which sensors to use

I'll firstly decide on the variables and with them decided I'll choose the sensors.

Measurements:

• Temperature and r. Humidity these are no brainers.
• CO2 is pretty important for my everyday life. In school I can't even open windows because of my classmates
• VOC, HCHO for when working in an enclosed spaces in winter. I sometimes paint or do some stupid stuff...
• PMs great for everyday life. And also for soldering, sanding and other workshop stuff. Oh yeah our electronics club sometimes gets super smoked out with solder fumes lol.
• I would also love to know Ground level ozone because it seems pretty important.

Activities

assumptions of what will be affected by which activity

Aikido

• Temperature will slightly increase
• humidity will rise
• CO2 will spike quite hard
• PM10 may see a spike as well

Collage in winter

• Temperature will increase as our school saves on thermal energy and we are freezing there.
• humidity will rise
• CO2 will spike quite hard, because my schoolmates doesn't want to open windows because it's cold
• I keep smelling a pretty funny smell when entering the class, so maybe HCHO or VOCs might spike.
• sound polution

3D printing

• Temperature will rise
• VOCs will be produced along with Formaldehyde
• and maybe PM will do something

Electronics club

• Temperature will slightly increase
• humidity will rise
• CO2 will spike, we have open windows there.
• PM10 will rise because of soldering fumes, VOCs maybe too

Sensor selection:

• As a base I chose SEN66 with measurements of PM, RH/T, VOC, NOx and CO2
• SFA30 for Formaldehyde ### These may be changed for other ones.
• There aren't a lot of options for Ozone sensors but this one looks promising. https://www.dfrobot.com/product-2005.html
• And maybe a LTR390UV or AMS AS7331 and TDK ICS43432 for UV and sound polution. I'm not really sold on these sensors yet.

2/15/2026 - SGP41

So I've got my hand on SGP41 sensor and and thanks of the work of oscgonfer and Coloradohusky and it measures great! I'm really exited for this project and for revamping the enviroment metrics for the better.
This sensor is going to go into Travel Buddy!

https://github.com/meshtastic/firmware/pull/7198

3/21/2026 - Strated work on the CAD; Roughly decided on the design

With the help of AI I was able to make a table over viewing the sensor which I planned to use. Like a month ago...
Now with 20 days until the blueprint deadline I have to scale back the scope.

That's why I've settled on using only the SEN66 with the heltec t114. I'm also super keen on adding a microphone nut I have a few at hand. But that will be for later.

After thinking of an elegant design I have came up with a slanted screen with the SEN on the back.

Did a few markups on paper and it looks promising. And it will look super smart!

Then I've jumped into CAD found the needed reference models for the SEN66 and the heltec t114. made an assembly for the sen and based my design of off it.

PS: I need to go to CT studios so adios

3/24/2026 - Tried integrating the heltec T114

Oh boy I'm struggling to come up with the right design today, even though I had the entire afternoon. Yeah nothing just works. A lot of the times I'm doing CAD the ideas just flow and I'm able to come up with a beautiful design. But not today. I's probably because I was attending a lot of competitions and events.

Yeah I'm not counting today as a super productive day. But every UP and DOWN should be documented so that's why I'm sharing my struggles. ;)

The journal isn't as juicy as there is with other days. So excuse me please. - Mainly images this time

I'm struggling with CADing up this design and I'm tight on time. The recepie for dezister.

I've managed to make it via a loft.

This doesn't seem right.

I don't know where to put the battery.

Even thought it looks decent there is no space for the intended 5Ah battery or for even a smaller one. Yeah so hopefully I'll be better tomorrow bye.

Even though I sat on it for like 7 hours I think it's appropriate to count 5.

Also I'm starting to doubt if this project is going to get accepted as I don't see it as fitting for blueprint. Going to ask in slack TMRW.