5 ms·

Iam looking to build my own CO2 Meter for a while know. I even thought about making a little series as christmas presents. My struggle always was to pick the r

by lhoff 7y ago

Iam looking to build my own CO2 Meter for a while know. I even thought about making a little series as christmas presents. My struggle always was to pick the right module. Its so hard to pick one and really trust it when you don't have a reference. So i thought maybe i give this sensor a shot but i can't find a reputable source for it. Does someone knows where to buy it or uses another module that works good?

mataug 7y ago
+1 on this, Where does one buy a reliable indoor sensor ?
petsfed 7y ago
I'm fond of the Sensirion SCD30. Its low cost, low power, and easy to interface with. A lot of NDIR CO2 sensors pull 5V, so the sensirion's 3.3v power is nice. Digikey is currently out of them, but SparkFun has them in stock. Nice for hobbyists! CO2meter.com is a good source for buying OEM CO2 sensors, although a little too coy with manufacturer's data sheets, in my opinion. Virtually all NDIR CO2 sensors use some sort of automatic calibration, where the lowest reading in a certain period of time is assigned the value 450ppm. If that's accurate for your area and you can guarantee that the space the sensor is monitoring is unoccupied during that period of time, its not bad. Otherwise, a reference gas is the only way to really trust the readings.
- deleted 7y ago
  [deleted]
gsich 7y ago
mh-z14 or mh-z19. Automatic calibration can be disabled.
- ClumsyPilot 7y ago
  I use those, on ESPHome and connected to homeassistant. They seem to provide reasonable readings
411111111111111 7y ago
i was shopping around last year as well. i finally went with `TFA Dostmann AirControl Mini CO2 Meter`, you can get the data pretty easily [1] if you connect it to a raspberry pi (or any linux system, really), so i'm currently pushing it through MQTT to my HomeAssistant. i was really surprised when i started monitoring it how closely related my concentration is to the co2 ppa in my home. [1] https://github.com/maddindeiss/co2-monitor https://github.com/maddindeiss/co2-monitor
- Arkanosis 7y ago
  This is a great device. We've never had windows open as much as since we have it, and believe me, it means a lot of headaches that go away every week without any coffee or paracetamol. The next time we move house, proper ventilation is definitely one of the first things we'll check.
- xenonite 7y ago
  This device is a rebranded RAD-0301 meter. In Germany, this brand seems to be the easiest way for purchasing the RAD-0301.
throwaway9d0291 7y ago
+1 for Sensirion's SCD30 [0], or even better when it comes out, SCD40. I've tested a lot of different sensors and the SCD30 is more expensive than the Chinese sensors but in my experience it's much more accurate. The problem with all of these sensors is calibration. They naturally drift over time so you need some way to compensate for that. There are a few common approaches: - Assume that every single day, the sensor is completely immersed in fresh air at some point - this is the way the MH-Z19 series of sensors works. It can make sense in business HVAC systems where it's common to do a fresh air purge every 24h but in a residential environment it's unreliable because there's no guarantee that a room will return to fresh air levels of CO2 (e.g. if a room only has 3-4h unoccupied and the windows aren't open, it might not return to 400ppm). To be clear, this isn't a problem unique to the Chinese sensors. There are also expensive sensors from major and reputable manufacturers that act this way, again, because it's common in commercial HVAC systems to do a daily fresh-air purge. - The above but a bit more intelligent - this is the SCD30's method: it looks at the previous 7 days of data and only if there were at least 5 days where the baselines are within 50ppm of each other, treats the average of those baselines as the fresh air concentration. This makes it fantastic for residential applications. Even if your room's CO2 levels don't return to 400ppm every day, as long as they don't consistently return to another baseline, the auto-calibration cycle won't run and mess up your data. - Manually do a baseline calibration every few months: make the user take the sensor outside into fresh air (or vent a building with fresh air) and tell the sensor "the CO2 concentration right now is 400ppm" - this is the only way the MH-Z19 and similar sensors can really be made anything close to accurate. Also, make sure to avoid anything other than NDIR sensors. There are a lot of "eCO2" sensors that give you estimated CO2 levels based on VOCs, which always results in garbage readings. Finally, you can usually buy the SCD30 very easily. It's routinely stocked by electronic component distributors so you can just look it up in OctoPart[1]. Make sure to avoid the eval kits though. [0]: https://www.sensirion.com/en/environmental-sensors/carbon-dioxide-sensors/carbon-dioxide-sensors-co2/ https://www.sensirion.com/en/environmental-sensors/carbon-di... [1]: https://octopart.com/search?q=Sensirion+SCD30&currency=USD&specs=0 https://octopart.com/search?q=Sensirion+SCD30&currency=USD&s...
- toasted_flakes 7y ago
  > it looks at the previous 7 days of data and only if there were at least 5 days where the baselines are within 50ppm of each other, treats the average of those baselines as the fresh air concentration. Is that documented anywhere? I couldn't figure out why mine is reading garbage, it could be that it didn't see fresh air every day for a full week

by lhoff 7y ago

mataug 7y ago

+1 on this, Where does one buy a reliable indoor sensor ?

petsfed 7y ago

I'm fond of the Sensirion SCD30. Its low cost, low power, and easy to interface with. A lot of NDIR CO2 sensors pull 5V, so the sensirion's 3.3v power is nice. Digikey is currently out of them, but SparkFun has them in stock. Nice for hobbyists! CO2meter.com is a good source for buying OEM CO2 sensors, although a little too coy with manufacturer's data sheets, in my opinion. Virtually all NDIR CO2 sensors use some sort of automatic calibration, where the lowest reading in a certain period of time is assigned the value 450ppm. If that's accurate for your area and you can guarantee that the space the sensor is monitoring is unoccupied during that period of time, its not bad. Otherwise, a reference gas is the only way to really trust the readings.

deleted 7y ago
[deleted]

gsich 7y ago

mh-z14 or mh-z19. Automatic calibration can be disabled.

ClumsyPilot 7y ago
I use those, on ESPHome and connected to homeassistant. They seem to provide reasonable readings

411111111111111 7y ago

i was shopping around last year as well. i finally went with `TFA Dostmann AirControl Mini CO2 Meter`, you can get the data pretty easily [1] if you connect it to a raspberry pi (or any linux system, really), so i'm currently pushing it through MQTT to my HomeAssistant. i was really surprised when i started monitoring it how closely related my concentration is to the co2 ppa in my home. [1] https://github.com/maddindeiss/co2-monitor https://github.com/maddindeiss/co2-monitor

Arkanosis 7y ago
This is a great device. We've never had windows open as much as since we have it, and believe me, it means a lot of headaches that go away every week without any coffee or paracetamol. The next time we move house, proper ventilation is definitely one of the first things we'll check.
xenonite 7y ago
This device is a rebranded RAD-0301 meter. In Germany, this brand seems to be the easiest way for purchasing the RAD-0301.

throwaway9d0291 7y ago

+1 for Sensirion's SCD30 [0], or even better when it comes out, SCD40. I've tested a lot of different sensors and the SCD30 is more expensive than the Chinese sensors but in my experience it's much more accurate. The problem with all of these sensors is calibration. They naturally drift over time so you need some way to compensate for that. There are a few common approaches: - Assume that every single day, the sensor is completely immersed in fresh air at some point - this is the way the MH-Z19 series of sensors works. It can make sense in business HVAC systems where it's common to do a fresh air purge every 24h but in a residential environment it's unreliable because there's no guarantee that a room will return to fresh air levels of CO2 (e.g. if a room only has 3-4h unoccupied and the windows aren't open, it might not return to 400ppm). To be clear, this isn't a problem unique to the Chinese sensors. There are also expensive sensors from major and reputable manufacturers that act this way, again, because it's common in commercial HVAC systems to do a daily fresh-air purge. - The above but a bit more intelligent - this is the SCD30's method: it looks at the previous 7 days of data and only if there were at least 5 days where the baselines are within 50ppm of each other, treats the average of those baselines as the fresh air concentration. This makes it fantastic for residential applications. Even if your room's CO2 levels don't return to 400ppm every day, as long as they don't consistently return to another baseline, the auto-calibration cycle won't run and mess up your data. - Manually do a baseline calibration every few months: make the user take the sensor outside into fresh air (or vent a building with fresh air) and tell the sensor "the CO2 concentration right now is 400ppm" - this is the only way the MH-Z19 and similar sensors can really be made anything close to accurate. Also, make sure to avoid anything other than NDIR sensors. There are a lot of "eCO2" sensors that give you estimated CO2 levels based on VOCs, which always results in garbage readings. Finally, you can usually buy the SCD30 very easily. It's routinely stocked by electronic component distributors so you can just look it up in OctoPart[1]. Make sure to avoid the eval kits though. [0]: https://www.sensirion.com/en/environmental-sensors/carbon-dioxide-sensors/carbon-dioxide-sensors-co2/ https://www.sensirion.com/en/environmental-sensors/carbon-di... [1]: https://octopart.com/search?q=Sensirion+SCD30&currency=USD&specs=0 https://octopart.com/search?q=Sensirion+SCD30&currency=USD&s...

toasted_flakes 7y ago
> it looks at the previous 7 days of data and only if there were at least 5 days where the baselines are within 50ppm of each other, treats the average of those baselines as the fresh air concentration. Is that documented anywhere? I couldn't figure out why mine is reading garbage, it could be that it didn't see fresh air every day for a full week