Smallest particulate matter air quality sensor for ultra-compact IoT devices
bosch-sensortec.com
bosch-sensortec.com
> Laser light is emitted from the sensor and focused by the sensor lens at approximately 5 mm from the top of the sensor’s lens surface.
> Particles traveling in free space due to the natural ambient airflow are detected when passing through the laser focal (sensitive) region.
> Due to the interaction between particles and light, the light scatters in different directions; a fraction is back-scattered towards the sensor, where the integrated photo-detectors detect it.
> The back-scattered signal is processed by unique algorithms (based on particle counts, particle relative velocity, probed air volume during measurement) to derive the particulate matter mass concentration.
You want to count particles per volume of air, so conventional sensors use a fan to have a constant volumetric flow and then count particles per second to infer particles per volume.
The way I interpret the above marketing language is that they use the optical sensor not only to count particles but also to measure the particle movement and infer airflow. So as long as there is some natural movement in the air, they can measure both particle count and volumetric flow, and thus infer particles per volume.
We actually have a sample of the Bosch in our office but haven’t come along to test it yet. Maybe with this call, I will get our team onto it.
The form factor has pros and cons in my opinion. The size and lower energy consumption definitely opens new applications but the problem is that it needs a clear field of view to do the measurements.
This could in turn restrict the applicability, eg as a wearable sensor.
In general I think it’s great to see innovations in the PM sensor field but often minimizations go on costs of accuracy.
We saw that for example with the Sensirion photo acoustic CO2 SCD4x sensor that is tiny but needs more black box algorithms to compensate for certain environmental conditions that then limits the range of applications.
I've been messing around with air quality measurement for a while but haven't got anything for the day to day yet.
Been a long time admirer of the Airgradient project. What are your thoughts on the SEN5x Vs Plantower PM sensors?
It might be better than the Plantower but on the other hand we know the Plantower really well now after 10s of thousands of units going through our test chamber. This allows us to tweak the Plantower to really good performance.
I bought a 10-in-1 air quality sensor with USB-C, and it won't do USB-C PD.
Batteries for when the power is out make sense.
Which air quality sensor integrates the most sensors of all?
Curious if there are any maintenance requirements for the bosch sensor.
As someone who manages commercial building automation system installations, I have never understood the obsession that HN has with residential IAQ sensors. The number will go up if you cook, burn a candle, use a hairdryer, or if there’s wildfire smoke outside and you have a ducted HVAC installation with an outdoor air intake.
In a commercial BAS, IAQ sensors (CO/NO to be more specific) are used to turn on exhaust and make-up air fans to increase the air quality in a space, but in every single thread about IAQ monitoring on HN, nobody ever seems to use the sensor readings to automate their HVAC equipment to do anything. In fact, almost all commercial BAS systems have zero IAQ sensors (especially in offices), the vast majority of them are use for turning on exhaust fans and make-up air units in buildings where cars are driving inside, like a parking ramp or drive-in warehouse.
I guess my question is, why collect this information and do nothing with it? Maybe you actually do something with it, or you monitor local outdoor air quality as a hobby. I’m asking a more general audience than you specifically.
Lastly, ensuring your house is positively pressurized by paying a testing and balancing contractor to come over and adjust your HVAC system will do more to keep out particulate matter than measuring it ever will.
I live in an old 1930s house in the UK so no HVAC or anything more automatable sadly
In the time since I’ve found it helpful for: confirming my DIY air purifier was effective during wildfire smoke periods, having a reminder to open the windows generally when the air gets stale and particularly after cooking, learning that cracking a window for makeup air for the range hood makes it much more effective, getting better about trimming candle wicks and snuffing them instead of blowing them out, getting a sense of our actual temp and humidity comfort ranges and how they differ from thermostat settings, and realizing that induction really might be preferable to gas whenever we’re looking to buy a stove in the future.
It's rather dumb at the moment, but when number gets too high, it kicks on for 1 hour and if it's back below threshold it shuts off. There's also a human presence detector that will "pause" it for 5 minutes since it's in my kitchen window.
It's built out of cardboard (laminated, with wheat paste) as a proof of concept/tinker with design and placement of things and also serves as a platform for the cats to nap in the window.
This, mainly, helps from bringing in all the outside humidity during the summer and the bitter cold during the winter. Otherwise, prior, I'd just keep an exhaust fan running all the time (eating the losses on air conditioning/heat) but we'd end up closing the window when it was super hot/cold and then the iaq would get terrible.
Lots and lots of people are automating their various systems due to monitoring these values. An application I've seen lots of is to just kick on the hvac systems fans when the aq drops below a particular threshold in one room or another.
> Lastly, ensuring your house is positively pressurized by paying a testing and balancing contractor to come over and adjust your HVAC system will do more to keep out particulate matter than measuring it ever will.
Sadly, it took me a while to figure out that having this window fan in my kitchen on "exhaust" rather than "intake" was creating a negative pressure environment and that was.. not optimal.
That’s awesome! A cardboard POC that actually works is a cool project.
> Sadly, it took me a while to figure out that having this window fan in my kitchen on "exhaust" rather than "intake" was creating a negative pressure environment and that was.. not optimal.
Maintaining positive pressure is tricky, one thing that can help is monitoring outdoor air pressure and duct static pressure in the supply duct and controlling fans/dampers to maintain positive pressure by keeping indoor higher than outdoor.
How does this model deal with this?
You can detrend for high humidities, but once water condenses, the only way round this would be to add a drying instrument.
It's that fog is being detected as a particle. This distorts the measured values.
it might make people give a darn how bad it typically is everywhere now
But won't trust this sensor until there are tech comparisons by AirGradient and BreatheSafeAir.com
Cost is one, but this isn't something you can measure quickly on demand, you want to keep averaging multiple measurements over time. So unless you want to hold out your phone for minutes to get a measurement it doesn't seem practical.
> Discover the PurpleAir PIXEL, one of the first end devices featuring the BMV080 particulate matter sensor for precise local air quality measurement. This user-friendly device provides real-time PM2.5 readings with a quick response time, clearly displayed via LED indicators. The BMV080‘s fanless design ensures completely silent operation, making it both effective and unobtrusive.
https://www2.purpleair.com/products/purpleair-pixel
That's the form factor you'd be looking at when its included with the rest of the supporting circuitry and logic.
So... possibly might be able to get it into a smaller package if the data display is externalized (Purple Air uses LEDs).
My parents are interested in this as one of their use cases is to put it on their e-bike so that they can be made aware of worsening air conditions after they've left the house.
This is great for flexibility but very impractical especially for DIY space. Hopefully small fully integrated modules on something like edgeconnector PCB come out soon enough.
Sparkfun sell a module with a ground plane + thermal pad as heat sink. This is suggested as OK by Bosch, though adding a small heatsink is probably a good idea, or just mount the enclosure on a metal surface.
https://www.sparkfun.com/sparkfun-air-quality-pm1-pm2-5-pm10...
https://www.bosch-sensortec.com/media/boschsensortec/downloa...