[HN Gopher] AirGradient Open Source Air Quality Monitor for CO2 ...
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AirGradient Open Source Air Quality Monitor for CO2 and PM2.5
Measurements
Author : ahaucnx
Score : 235 points
Date : 2023-01-29 19:42 UTC (3 hours ago)
(HTM) web link (www.airgradient.com)
(TXT) w3m dump (www.airgradient.com)
| aedocw wrote:
| For folks who want to do something similar (no CO2 measure, and
| possibly less accurate) for far less per sensor, you can easily
| connect an ESP8266 ($5) to an IKEA VINDRIKTNING ($16) air quality
| sensor[1]. Stick a AM2302 ($7) on the outside and you get PM2.5,
| temperature and humidity for about $30.
|
| [1]: https://style.oversubstance.net/2021/08/diy-use-an-ikea-
| vind...
| M3L0NM4N wrote:
| I will note though, CO2 measure indoors can be very valuable.
| Higher levels of CO2 result in less brain function, as shown by
| this Tom Scott video: https://youtu.be/1Nh_vxpycEA
| reeckoh wrote:
| They can also be a canary for other issues, like mold
| accumulation.
| PaulBGD_ wrote:
| I have both a modded VINDRIKTNING and the airgradient, imo the
| airgradient is worth it if you want everything in one package.
| More accurate than the ikea, a nice screen/case, and you don't
| have to strap a humidity sensor to the outside. Plus CO2 is
| great, more people need CO2 detectors.
| RobotToaster wrote:
| It isn't open source as it's under a NC licence, which restricts
| the field of endeavour.
|
| https://www.oshwa.org/faq/#non-commercial
|
| https://opensource.org/osd
| pigtailgirl wrote:
| -- live in seoul - air quality is sometimes "unbreathable" -
| using AirIQ api for smart home alert -
| https://www.iqair.com/us/air-pollution-data-api --
| sc00ty wrote:
| I ordered two DIY pro kits (with the TVOC sensors) earlier this
| month and went to start working on them yesterday. After flashing
| the firmware, neither one would create a hotspot for me to
| connect to. Looking at them and doing some googling, i found they
| include knock-off Wemos D1 minis (labeled "mimi"). It looks like
| they're aware there are Wi-Fi issues, but the chips are still
| being used [0][1]. I sent in an email yesterday but I'm not
| expecting a response until at least tomorrow.
|
| [0]: https://www.airgradient.com/open-airgradient/blog/d1-mimi/
|
| [1]: https://forum.airgradient.com/t/issues-with-new-dyi-pro-
| pres...
| patja wrote:
| A project I did to make CO2 monitors with a Sensiron SCD41 sensor
| and Adafruit MagTag e-ink module:
|
| https://www.printables.com/model/121265-salud-co2-monitor
| edge17 wrote:
| Just out of curiousity, what are the equivalent commercial
| products in this space?
| wallflower wrote:
| The IQAir is very nice. There is also the Purple Air monitor.
|
| https://www.iqair.com/us/air-quality-monitors
|
| https://www.purpleair.com
| erinnh wrote:
| Totally not a judgement about the quality of it, but it
| amazes me how the IQAir is only supported via Cloud. Even for
| this really local information I need to contact some Cloud to
| be able to get the information into my smart home.
|
| This stuff annoys me a lot.
| ahaucnx wrote:
| Yes unfortuntately we see a clear trend among other
| companies towards walled gardens, closed data and forcing
| people into subscriptions. We at AirGradient do not support
| this development and made very clear statements on our
| website.
| dgacmu wrote:
| You can connect to it via SMB and grab the raw logfiles. It
| stores them as csv.
|
| https://www.iqair.com/us/newsroom/download-the-airvisual-
| nod...
|
| Not a friendly API for integrating but you can build from
| there (I have an air visual pro and I do this)
| erinnh wrote:
| Thank you. The only info I found was their cloud
| connection.
|
| I was interested because I wouldn't have to deal with
| customs in their case, but considering the price and
| interesting integration, dealing with customs might be
| better :P
| newZWhoDis wrote:
| I was gifted an air things and had this exact problem.
| Local WiFi device is useless, stores everything in their
| cloud and takes forever to load randomly.
| wodenokoto wrote:
| I believe this is to support their pollution maps and
| pollution forecasts. Which makes the high price of the
| product odd to me.
| marcel_hecko wrote:
| Well we do a version with multiple uplink technology option and
| a full SDK[1]. The market is actually quite segmented depending
| on the final use case. This is IMO mostly because of the price
| of these devices. The CO2 probe itself is costly especially if
| metrologically calibrated so if you want one for every room in
| the school / office / home its not insignificant investment.
|
| I'll include a link to our datasheet [1] as to actually answer
| the question hoping Im not breaking HN rules.
|
| [1] https://docs.moirelabs.com/scoria-datasheet/
| zokier wrote:
| Vaisala has some air quality monitors, although they seem more
| oriented towards outdoors use?
| https://www.vaisala.com/en/products/weather-environmental-se...
| ahaucnx wrote:
| We also offer a fully certified commercial product (AirGradient
| ONE) focusing on B2B (Offices, Schools). Then you have monitors
| from other companies e.g. Awair, AirThings, Kaiterra, Air
| Visual etc measuring similar air quality parameters.
|
| We try to set us apart by promoting open data standards, clear
| data ownership, long lasting products that are easy to repair
| and maintain. More details on our main website [1].
|
| [1] https://www.airgradient.com/
| maweki wrote:
| Is it common for the HN audience to be able to fabricate their
| own PCBs? I believe none of my local hacker spaces have
| fabrication facilities.
|
| Whenever I see that, it means having to pay somebody quite a bit
| instead of do it yourself.
| Kuinox wrote:
| I built one. But without PCB. I just used wires and soldered
| it.
| idiotsecant wrote:
| You _can_ make your own PCBs quite easily with cheap chemicals,
| a laser printer, and some tubs to agitate the mixture. It 's a
| bad idea though, when you can design them and get them made
| online _incredibly_ cheaply.
| ted_dunning wrote:
| It is incredibly easy to use an on-line service to specify and
| fabricate PCBs.
|
| I just did it for an adapted multi-sensor temperature system
| and the boards were about $5 and tooling costs were minimal.
| The quality far exceeded anything that I have ever been able to
| do by myself.
|
| Self-etching is a royal pain for a medieval quality result. It
| probably winds up costing more than ordering the boards from
| PCBWay or similar manufacturer.
| aidenn0 wrote:
| I haven't had any made in a while but last time I got 2 index-
| card sized PCBs with silk-screen and solder mask for under $40
| after shipping.
| dgacmu wrote:
| There are some home-brewable ways for single layer boards,
| particularly one sided -- you can do the old school copper
| board + mask + etch with something like ferric chloride. It's
| pretty easy but you do want to be careful as the chemicals are
| a bit nasty. Newer school is to print the mask and transfer
| using a laminator.
|
| You can also physically etch with a milling machine. It's a bit
| more expensive but low startup cost if you already have a small
| cnc mill. You probably have access to one at a maker space.
| That's most likely the easiest way to go.
| jazzyjackson wrote:
| I guess I wouldn't say common - but hackerspaces and especially
| fablabs will often have a Roland CNC machine capable of carving
| PCBs out of copper-coated-fiberglass - but once you go through
| all that (paying for a couple broken 1/64" routing bits as you
| learn to use the machine...) it starts to make sense to pay $5
| per square inch at oshpark
| dragontamer wrote:
| Each time I see these, I feel a bit weird because they all rely
| upon a specific sensor, and the software / electronics is barely
| above beginner level.
|
| A PM2.5 sensor is based off of infrared LEDs and photodiodes.
|
| CO2 however is harder for me to understand. Does anyone know how
| that works?
|
| Temperature is easy: just a calibrated thermistor.
|
| Humidity: I dunno and am also curious.
|
| --------
|
| It's be a lot more comfortable for me to call this open source if
| the sensors actually gave design control to the engineer, more so
| than just assembly.
| breput wrote:
| The Senseair S8 CO2 sensor[0] used in this project also uses an
| infrared LED and works on the principal that CO2 absorbs
| certain frequencies of light.
|
| So if you know the brightness of the LED and the volume of air
| between it and the sensor, you can calculate the amount of CO2
| by comparing the expected vs. received light intensity.
|
| [0]
| https://rmtplusstoragesenseair.blob.core.windows.net/docs/pu...
| dragontamer wrote:
| Good to know.
|
| So methinks that a CO2 sensor would have to be based off of
| multiple LEDs + Photodiodes, to measure the absorbed light at
| _different_ frequencies. (LEDs and Photodiodes typically are
| only active at one frequency: such as 900nm or 700nm).
|
| If "all" frequencies are deflected, its PM2.5 (some particle
| got in the way of the measurement).
|
| If "some" frequencies are deflected, then its CO2.
|
| ----------
|
| The question after that comes down to calibration and test
| data. Is there an easy way to create CO2 density and/or PM2.5
| particles of a certain density?
|
| ---------
|
| There's a big difference.
|
| 1. Photodiodes and LEDs are extremely common parts
| manufactured by a wide variety of companies around the world.
| By tying yourself to Photodiodes/LEDs, you are less tied to
| any particular company.
|
| 2. Photodiodes and LEDs are well under 10-cents each. Though
| some more carefully calibrated ones / specialty ones may
| reach as high as $1 to $2.
| breput wrote:
| > (LEDs and Photodiodes typically are only active at one
| frequency: such as 900nm or 700nm).
|
| That's not entirely correct. The spec sheet for the LED
| will give an intensity vs. frequency chart, which depending
| on the LED can be 10s to 100s of nanometers wide. As long
| as the source LED has a sufficiently bright output in one
| of the CO2 absorption bands, it doesn't have to be exactly
| tuned like a laser.
|
| NDIR is the technology used in most consumer-grade CO2
| sensors:
| https://en.wikipedia.org/wiki/Nondispersive_infrared_sensor
| [deleted]
| pbronez wrote:
| Anyone know how hard it would be to convert this from USB-C power
| & wifi connectivity to PoE for power + data?
|
| TI has PoE chips for around $4, but I don't know enough about
| electrical engineering to figure out how to swap that into this
| design.
|
| https://www.ti.com/product/TPS23861
| pbronez wrote:
| Looks like you can get a PoE to USB-C adapter for $35:
|
| Revotech PoE to Type-C Adapter Converter, Convert POE to Output
| 5V/2.4A USB C with Ethernet, IEEE802.3af with 10/100Mbps ,
| Wired Broadband and PD Charging for Smart Phone/Tablet, Plug
| and Play (P2C5V) https://a.co/d/7320MNa
|
| Wonder how complex it is to access the network this way. If you
| have to modify the USB implementation you may as well skip the
| adapter and add an RJ45 + internal PoE chip...
| Tempest1981 wrote:
| I have a handheld $65 TVOC meter, but it's tricky to get
| repeatable measurements. It needs 5-10 minutes to warm up, but
| then the reading jump around almost 2x. It has 4 digits of
| resolution, but 1 digit of accuracy?
|
| Regardless, indoor TVOC levels increase significantly over 2-3
| days. Then opening the windows brings them back down. Not sure if
| that's normal. (TVOC = Total volatile organic compounds)
|
| Any recommendations for quality sensors?
| ahaucnx wrote:
| Compared to CO2 and PM measurements, TVOCs are the most
| difficult to measure because they encompass a wide range of
| chemicals that trigger the sensor. Some are very harmful, e.g.
| aggressive paint and others (hopefully) harmless like
| sunscreen. Both trigger the sensor.
|
| Additionally the sensors are only showing you correct absolute
| levels in lab conditions, e.g. using ethanol at a specific
| temperature and humidity. So in real environments, the absolute
| values are pretty useless.
|
| We now use a newer generation of TVOC senor e.g. the SGP41 that
| is more index based and eliminates the issue of the absolute
| values.
|
| We also observe that temperature and humidity can influence the
| TVOC measurements.
|
| All in all, TVOC is good to detect spikes and check what is
| causing these, e.g. use of aggressive cleaning chemicals.
| However the absolute levels in e.g. ppb should better be
| ignored.
|
| Yes, it is normal that fresh air flushes out chemicals and you
| can see this improvement. We do like the SGP4x series from
| Sensirion for TVOC sensors.
| drakenot wrote:
| Are they accurate enough for me to ensure I'm keeping VOC
| levels down while 3D printing different materials?
| ahaucnx wrote:
| Yes I think they should be suitable for that.
| ted_dunning wrote:
| That could be an excellent use for sensors that only give
| reasonable relative measurements.
| parker_mountain wrote:
| FWIW, TVOCs can collect together and move around in "waves",
| your indoor air is not just one big evenly distributed "soup".
| The sensors also have lots of factors that affect them, such as
| humidity - you can usually find more info in the docs for the
| sensor part.
|
| A better approach would be to sample consistently and use that
| to build a graph showing TVOC ppm over time.
| 1270018080 wrote:
| Does anyone know of air quality monitors that check for NO2 as
| well as CO2?
| NikolaNovak wrote:
| Open source diy is wonderful. But is there a reliable trustworthy
| monitor that can just... Be bought? A box that will reliably tell
| me what's the carbon dioxide carbon monoxide dust allergens
| volatile compounds? Am I possibly being greedy and I need several
| konitors (I wouldn't have an issue with that)?
|
| Every review I check for any consumer accessible device seems to
| indicate they're inaccurate, miscalibrated, or downright
| deceptive :-(
| ahaucnx wrote:
| PM, CO2, temperature and humidity can be fairly accurately
| measured with consumer monitors provided they use good sensors.
|
| You can check if the monitor is RESET AIR certified which is an
| independent and 3rd party test against reference devices.
|
| https://www.reset.build/directory/monitors/air
| pfyy wrote:
| We made a small co2 sensor based on the sensirion scd30 and m5
| stack. If you want a portable sensor with battery and display,
| you might be interested. Source code is on
| https://github.com/smoca-ag/m5stack_co2_sensor
| crazygringo wrote:
| This is tangential, but is anyone aware of a live outdoor CO2
| levels map? I've never been able to find one anywhere.
|
| Because outdoor levels seem to vary significantly in a kind of
| 400-600 range, and it's impossible to calibrate a sensor outside
| without a reference point. On a windy winter day you can probably
| assume it's close to the global ~414, but on a muggy still summer
| day my sensors usually read significantly higher when holding
| them outdoors.
| keenanj wrote:
| This is a plug for my non-profit building an open-source
| version of exactly that: ribbitnetwork.org.
|
| Our society deserves to have a publicly available map of
| outdoor emissions. There are lots of hard science and data
| analysis questions to solve in order to get there with reliable
| and cheap sensors, but I think it's a journey worth going on.
|
| We're on discord and GitHub if anyone wants to come build with
| us.
| crazygringo wrote:
| Thank you! That's exactly the kind of thing I was looking
| for.
|
| I've been utterly baffled by how atmospheric CO2 is one of
| the very top issues of our time, and yet... I can get live
| temperature, humidity, and things like PM2.5, PM10, NO2, O3,
| etc... but _not CO2_.
|
| Since you're in this area, do you have any insight as to why?
|
| There are thousands of official air quality monitors used all
| over the world for calculating AQI and similar. Why did they
| skip CO2? Is there something inherently difficult or
| inaccurate about measuring it, is its short-term variation
| simply seen as irrelevant to health and not worth studying,
| or is there a political fear that live monitoring might
| somehow become ammunition for climate change deniers, along
| the lines of every winter blizzard leading to some people
| taunting "where's your global warming now?"
|
| We measure CO2 at the Mauna Loa Observatory in Hawaii... and
| seemingly nowhere else?
| namibj wrote:
| You can use a chemical CO2 scrubber (e.g., bubbling air through
| a saturated solution of calcium hydroxide) to get a rather
| stable/repeatable sub-ambient reference to calibrate the sensor
| with.
|
| An aquarium bubbler , or rather two, should be easy to plumb to
| a CO2 sensor. Just skip the water bath for one of them.
|
| The calcium hydroxide is sold as "hydrated lime" and needs to
| just be stored isolated from CO2, and is mildly basic, so will
| slowly corrode your fingers (wash after touching, don't get any
| in your eyes).
|
| Shouldn't even need gloves for this usecase, where one
| occasionally swaps the water and sediment for fresh stuff.
|
| Btw, the waste, after soaking CO2, is just harmless limestone.
| Sprinkle around somewhat to make it a thin layer to ensure it
| all converts soon.
| breput wrote:
| Many CO2 sensors have a 0 ppm calibration setting option, so
| you can place them in a small container and fill it with a
| CO2-free gas such as nitrogen or even butane. Obviously
| nitrogen is safer although somewhat more expensive and more
| difficult to buy in small canisters.
|
| But realistically for home air quality measurements, it doesn't
| really matter. If you happened to calibrate it at 600 ppm you'd
| know when you later saw values below 400 ppm. Or you'd read a
| little high which probably isn't something you'd even notice.
| ahaucnx wrote:
| This is an updated version of our DIY air quality monitor that
| now includes a configuration button and some other PCB
| improvements around the I2C bus.
|
| It has also pin breakouts so you can easily add additional
| sensors if required. Hardware and software are both open source
| and can easily be adjusted.
| smcleod wrote:
| Nice! Great work making it open source!
| aikinai wrote:
| Is there any way to checkout without PayPal? I was mysteriously
| banned a few years ago with no details and no recourse. And I
| don't see an option to just pass through a credit card without
| logging in.
|
| Edit: Never mind! I found out tapping the credit card logo
| worked to do a pass through payment without logging into
| PayPal. Purchased!
|
| And thanks for supporting international shipping too!
| Youden wrote:
| Was the decision to use pin headers instead of SMD components a
| conscious choice?
|
| For the particulate sensors it's unavoidable but you can use
| Sensirion's SCD4X series for CO2, just about any VOC chip you
| want, and an ESP32 module instead of dev board.
|
| It should be substantially cheaper overall since the components
| can be ordered in bulk and the only assembly needed would be
| the particulate sensor.
|
| I've been meaning to get around to it myself but I still
| haven't settled on how to power it. I'm really tempted to try
| stuffing it full of giant batteries so that it can run for at
| least around a year without a cable.
| comboy wrote:
| If you want continuous measurement, battery is pretty much
| not an option, PM2.5 will use a small fan, so even at 30mA
| it's 30 * 24 * 365 so for a year you need 262,800mAh battery,
| it's a different voltage but to put it in context your laptop
| is likely under 10,000mAh. If you only need to take
| measurements say every 30mins then sure, but then either you
| worry about sending it somewhere and receiving it or you need
| to use additional battery power for displaying it.
| ahaucnx wrote:
| Most people find it easier to solder through holes than SMD.
| We use SMD in our commercial product.
|
| We are testing the SCD4x and like it so far. It might be a
| future option.
| Youden wrote:
| I guess what I'm asking is does it need to be hand-
| solderable? With places like JLCPCB offering cheap SMD
| assembly, SMD boards are still accessible to hobbyists.
| mardifoufs wrote:
| I though JLPCB only assembled components that are
| available in their catalogue. If they don't have the part
| you need, you'll have to hand assemble it. These are
| pretty niche components, with odd footprints and size so
| I'd be surprised if assembly was available.
| kayson wrote:
| Wish I had seen this before I bought all the constituent parts on
| sparkfun! Though I do have some concerns about the accuracy of
| the PM2.5 sensor (mainly because the data sheet isn't
| exceptionally clear).I ended up getting the Sensirion equivalent
| over this one even though its quite pricey.
|
| Every all-in-one air quality monitor I've seen except one omit
| some fairly important metrics - NO2 and hydrogen sulfides. I'm
| guessing it's because the sensors are extremely expensive (I got
| quotes for $90+/ea from one vendor). I ended up finding a
| startup, SPEC Sensors, that has much cheaper screen-printed
| sensors, and if their data sheets are to be believed, they're
| more than sufficient.
| fierro wrote:
| would love a blog post / tutorial for this set up including the
| expensive sensors. I think a lot of us who care about air
| quality don't mind spending a few hundred dollar for cool new
| data
| ahaucnx wrote:
| We have made very good experience with the Plantower PMS5003 PM
| sensor and thousands of them went through our test chamber. The
| plantower has also shown one of the best accuracies for low-
| cost sensors compared to reference stations in various studies.
|
| I agree that the data sheets from Plantower are not great.
| Unfortuntately this is often the case from Chinese
| manufacturers.
| kayson wrote:
| That's good to know! Have you published your testing results
| anywhere?
| comboy wrote:
| I second Plantower (I've only used a few PMS7003), it allows
| you to build a really high quality sensor while being really
| a beginner project using some arduino and LCD. Note that this
| is only for particulates in the air.
|
| Btw, why thousands? And any reasons for not using CCS811 for
| TVOC and HDC1080 for temp while you're at it? Sounds like you
| have tons of experience and it's not easy to find reviews
| which properly test these.
| ahaucnx wrote:
| No specific reasons other than that we are pretty happy
| with the quality from Sensirion and thus like to use their
| sensors.
| dheera wrote:
| I made something similar
|
| https://dheera.net/projects/airmonitor/
|
| I used a PMSA003I and had major problems with it -- it was
| always reporting 0 for AQI if the actual value was anywhere
| below ~100. It wasn't sensitive to low levels of pollution. Is
| the PMS5003 any better?
| ahaucnx wrote:
| We also used the A003 in the past and were not happy with
| accuracy and quality. We had quite a number of them failing
| early. The 5003 is a lot better in my opinion.
| dheera wrote:
| thanks!
| jph wrote:
| This is super-useful. The TVOC / NOx module is especially
| compelling. Can I purchase it pre-soldered?
|
| I do see your commercial offering (AirGradient ONE) and I'd like
| to buy that for my office. How does a typical consumer purchase
| one online?
| upon_drumhead wrote:
| They have pre-soldered kits in their store, which took me a hot
| minute to actually find.
|
| https://www.airgradient.com/open-airgradient/shop/
| ahaucnx wrote:
| The presoldered kit also comes already pre-flashed and you
| can literally build it in 5-10 minutes. Just need to plug in
| the sensors, one cable and screw it together.
| [deleted]
| arriu wrote:
| How does this compare to something like the Aranet4 module?
| ahaucnx wrote:
| It should give very similar results. As far as I know the
| Aranet also uses a CO2 Sensor from Senseair.
| pppone wrote:
| I would recommend checking out the AQ-SPEC program [1]. They do
| quite comprehensive tests on low-cost air quality sensors. My
| side project with a few friends [2] chose to use the Sensirion
| SPS30 [3] for our portable PM2.5 monitor. As mentioned by others,
| it's a bit more expensive than the PMS5003 used by AirGradient,
| but we preferred its documentation, company reputation, and form
| factor at the time of choosing (2019). The PMS5003 is perfectly
| capable, and has demonstrated good success with many
| projects/companies using the sensor (e.g. PurpleAir). However, a
| quick search suggests there are some issues with a recent batch
| of these sensors [4].
|
| [1]: https://www.aqmd.gov/aq-spec/sensors
|
| [2]: https://www.open-seneca.org/
|
| [3]: https://sensirion.com/products/catalog/SPS30/
|
| [4]: https://community.purpleair.com/t/new-version-of-
| plantower-p...
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(page generated 2023-01-29 23:00 UTC)