4 ms·

Finally an actually working (cheap?) CO2 sensor? So many of those actually measure humidity, temp and VOCs and try to derive some sort of CO2 reading out of th

Finally an actually working (cheap?) CO2 sensor? So many of those actually measure humidity, temp and VOCs and try to derive some sort of CO2 reading out of those.

IgorPartola 2y ago
This was my thought exactly. I used sensors that were about $25/each in the past and those worked well but this would be seemingly way easier to integrate and get ahold of.
- vardump 2y ago
  $25 for a CO2 sensor component that actually works is not bad at all.
  - tobi1449 2y ago
    Sensirion SCD41 should be pretty good, right? You can get them for ~25 USD on aliexpress ...
    - ale42 2y ago
      I'm not sure I would source non-Chinese electronic components from Aliexpress... (unless it's just to play with them, definitely not for a product): you might need to check their reliability and quality. Pretty sure that Sensirion themselves are not selling there, so they are probably either clones, fakes, recycled ones, or if you are lucky authentic ones that for some reason ended up there (but I can't imagine a way).
      - throwup238 2y ago
        > or if you are lucky authentic ones that for some reason ended up there (but I can't imagine a way). Chinese fabs are notorious for running secret shifts that make their customers’ chips to sell themselves. They’re the exact same chip but made without authorization, using the customer’s exact design. That said, Sensirion has their own CMOS fabs in Switzerland so that’s very unlikely to be the case here. If they work at all, the counterfeit chips are probably some Chinese CO2 sensor IC that's small enough to fit into the same package, lightly customized to fit the pinout of the original. Or it's just a microcontroller inside faking it a la FTDI.
        tobi1449 2y ago
        Huh, good points. It doesn't seem to be just a micro sensor faking it, as it reacts as expected for example when opening the windows. I guess the only way to tell if they are any good is to buy a verified good CO2 sensor and compare the outputs then.
    - radicality 2y ago
      I got mine from M5Stack and works quite well, I’m submitting data every 5 seconds using EspHome/HomeAssistant
fuzzy2 2y ago
Sensirion has the SCD40, which appears to be based on the same principle. It's much cheaper than the SCD30.
- _blk 2y ago
  Yes, SCD30 series are optical while SCD40 series are photoacoustic. STC series are thermal conductivity based. STC and SCD40 are smaller than SCD30 but less accurate if memory serves (check datasheet).
rainburg 2y ago
The Senseair S88, which was released earlier this year, costs ~$22/piece, or ~$13/piece if you order more than 100.
tzs 2y ago
It's not really "finally". They introduced a similar sensor, the PASCO2V01, a couple years ago. That one has been available on a breakout board with the necessary support hardware from SparkFun for over a year [1]. Comparing the datasheets for the PASCO2V01 and the new PASCO2V15 the old one actually seems a little better as far as CO2 measuring performance goes. They are the same on most things, but the old one has slightly better accuracy. The new one is ±(50 ppm + 5%) between 400 ppm and 3000 ppm. The old one is ±(30 ppm + 3%) between 400 ppm and 5000 ppm. The big difference is this: > Infineon has recently introduced the PASCO2V15, a new 5 V sensor to improve air quality monitoring in building environments. Both of them require a dual voltage power supply. They both want 3.3 V for their digital components and a higher voltage for their IR emitter. For the older one that higher voltage is 12 V. For the newer it is 5 V. [1] https://www.sparkfun.com/products/22956 https://www.sparkfun.com/products/22956
- fnordpiglet 2y ago
  Iirc they were merged into esphome last year too.
Animats 2y ago
True. The cheap ones are trying to guess CO2. Those are called "indoor air quality sensors". Small CO2 sensors have been available for years, for about $50. Compare [1]. Life of this new device is only 10 years, which is short for HVAC systems. A hotel might have a thousand of these. Older devices say "15+" years. All these devices have a calibration problem. They drift. They try to correct by treating the lowest value they ever see as "normal" (that's about 400 ppm CO2 today, vs 300 PPM in 1950) and recalibrating. So they're not useful for observing a general increase in CO2. They're also not useful for greenhouses, where CO2 levels may drop below ambient CO2 due to photosynthesis. Manual recalibration is possible but requires feeding in pure nitrogen and a known nitrogen/CO2 mixture.[2] Devices which don't need that re-calibration exist.[3] They're more complicated. Also don't seem to be stocked by the usual distributors. [1] https://rmtplusstoragesenseair.blob.core.windows.net/docs/publicerat/PSP107.pdf https://rmtplusstoragesenseair.blob.core.windows.net/docs/pu... [2] https://www.co2meter.com/blogs/news/7512282-co2-sensor-calibration-what-you-need-to-know https://www.co2meter.com/blogs/news/7512282-co2-sensor-calib... [3] https://www.murata.com/en-us/products/sensor/co2/overview/technicalinfo https://www.murata.com/en-us/products/sensor/co2/overview/te...
- brianglick 2y ago
  Do you know of anywhere at all to get one of the devices that don’t require re-calibration?
  - Animats 2y ago
    That is a really good question. Murata announced this in 2019, and there's a part number (IMG-CA0011-00/ IMG-CA0012-00/IMG-CA0023-00) and a full data sheet.[1] But no distributor has it. Not DigiKey, Mouser, Arrow, or Newark. Even Octopart doesn't list it. It's on Murata's list of recommended products, not the discontinued list. Try contacting Murata. [1] https://go.murata.com/rs/382-MEZ-125/images/HC%20CO2-sensor%20and%20microblower.pdf https://go.murata.com/rs/382-MEZ-125/images/HC%20CO2-sensor%...

Finally an actually working (cheap?) CO2 sensor? So many of those actually measure humidity, temp and VOCs and try to derive some sort of CO2 reading out of those.

IgorPartola 2y ago

This was my thought exactly. I used sensors that were about $25/each in the past and those worked well but this would be seemingly way easier to integrate and get ahold of.

vardump 2y ago
$25 for a CO2 sensor component that actually works is not bad at all.
- tobi1449 2y ago
  Sensirion SCD41 should be pretty good, right? You can get them for ~25 USD on aliexpress ...
  - ale42 2y ago
    I'm not sure I would source non-Chinese electronic components from Aliexpress... (unless it's just to play with them, definitely not for a product): you might need to check their reliability and quality. Pretty sure that Sensirion themselves are not selling there, so they are probably either clones, fakes, recycled ones, or if you are lucky authentic ones that for some reason ended up there (but I can't imagine a way).
    - throwup238 2y ago
      > or if you are lucky authentic ones that for some reason ended up there (but I can't imagine a way). Chinese fabs are notorious for running secret shifts that make their customers’ chips to sell themselves. They’re the exact same chip but made without authorization, using the customer’s exact design. That said, Sensirion has their own CMOS fabs in Switzerland so that’s very unlikely to be the case here. If they work at all, the counterfeit chips are probably some Chinese CO2 sensor IC that's small enough to fit into the same package, lightly customized to fit the pinout of the original. Or it's just a microcontroller inside faking it a la FTDI.
      - tobi1449 2y ago
        Huh, good points. It doesn't seem to be just a micro sensor faking it, as it reacts as expected for example when opening the windows. I guess the only way to tell if they are any good is to buy a verified good CO2 sensor and compare the outputs then.
  - radicality 2y ago
    I got mine from M5Stack and works quite well, I’m submitting data every 5 seconds using EspHome/HomeAssistant

fuzzy2 2y ago

Sensirion has the SCD40, which appears to be based on the same principle. It's much cheaper than the SCD30.

_blk 2y ago
Yes, SCD30 series are optical while SCD40 series are photoacoustic. STC series are thermal conductivity based. STC and SCD40 are smaller than SCD30 but less accurate if memory serves (check datasheet).

rainburg 2y ago

The Senseair S88, which was released earlier this year, costs ~$22/piece, or ~$13/piece if you order more than 100.

tzs 2y ago

It's not really "finally". They introduced a similar sensor, the PASCO2V01, a couple years ago. That one has been available on a breakout board with the necessary support hardware from SparkFun for over a year [1]. Comparing the datasheets for the PASCO2V01 and the new PASCO2V15 the old one actually seems a little better as far as CO2 measuring performance goes. They are the same on most things, but the old one has slightly better accuracy. The new one is ±(50 ppm + 5%) between 400 ppm and 3000 ppm. The old one is ±(30 ppm + 3%) between 400 ppm and 5000 ppm. The big difference is this: > Infineon has recently introduced the PASCO2V15, a new 5 V sensor to improve air quality monitoring in building environments. Both of them require a dual voltage power supply. They both want 3.3 V for their digital components and a higher voltage for their IR emitter. For the older one that higher voltage is 12 V. For the newer it is 5 V. [1] https://www.sparkfun.com/products/22956 https://www.sparkfun.com/products/22956

fnordpiglet 2y ago
Iirc they were merged into esphome last year too.

Animats 2y ago

True. The cheap ones are trying to guess CO2. Those are called "indoor air quality sensors". Small CO2 sensors have been available for years, for about $50. Compare [1]. Life of this new device is only 10 years, which is short for HVAC systems. A hotel might have a thousand of these. Older devices say "15+" years. All these devices have a calibration problem. They drift. They try to correct by treating the lowest value they ever see as "normal" (that's about 400 ppm CO2 today, vs 300 PPM in 1950) and recalibrating. So they're not useful for observing a general increase in CO2. They're also not useful for greenhouses, where CO2 levels may drop below ambient CO2 due to photosynthesis. Manual recalibration is possible but requires feeding in pure nitrogen and a known nitrogen/CO2 mixture.[2] Devices which don't need that re-calibration exist.[3] They're more complicated. Also don't seem to be stocked by the usual distributors. [1] https://rmtplusstoragesenseair.blob.core.windows.net/docs/publicerat/PSP107.pdf https://rmtplusstoragesenseair.blob.core.windows.net/docs/pu... [2] https://www.co2meter.com/blogs/news/7512282-co2-sensor-calibration-what-you-need-to-know https://www.co2meter.com/blogs/news/7512282-co2-sensor-calib... [3] https://www.murata.com/en-us/products/sensor/co2/overview/technicalinfo https://www.murata.com/en-us/products/sensor/co2/overview/te...

brianglick 2y ago
Do you know of anywhere at all to get one of the devices that don’t require re-calibration?
- Animats 2y ago
  That is a really good question. Murata announced this in 2019, and there's a part number (IMG-CA0011-00/ IMG-CA0012-00/IMG-CA0023-00) and a full data sheet.[1] But no distributor has it. Not DigiKey, Mouser, Arrow, or Newark. Even Octopart doesn't list it. It's on Murata's list of recommended products, not the discontinued list. Try contacting Murata. [1] https://go.murata.com/rs/382-MEZ-125/images/HC%20CO2-sensor%20and%20microblower.pdf https://go.murata.com/rs/382-MEZ-125/images/HC%20CO2-sensor%...