[HN Gopher] AirGradient Open Source Air Quality Monitor for CO2 ... ___________________________________________________________________ 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... ___________________________________________________________________ (page generated 2023-01-29 23:00 UTC)