Air quality node


  • Mod

    Hi
    I was thinking about building an air quality node and I found this sensor that could be the starting point. I am looking for opinions if it could be a good choice or there is something better.


  • Hardware Contributor

    Hello @gohan,

    you have this one (CCS811) and the BME680.
    The specific board your are linking to is a bad deal IMHO, as it's a CCS811 (available alone for less than half the price) + BMP280 + HDC1080 (si7021 "clone" but without the precious teflon filter). If you go for the CCS811 buy it separately and add a BME280 or si7021.

    I considered the 2 and decided to go for the BME680, here are the advantages of the 2 sensors (I may be wrong on some points and I'll be happy to get corrected if I make mistakes...)

    CCS811 :

    • integrated MCU to make calculations of the IAQ: you can use it even with an atmega MCU, and if you go for a Cortex M or ESP8266 you don't need to fiddle with the arduino installation to include the Bosch binary.
      -much lower cost and much wider availability on breakout boards

    BME680:

    • all included in one sensor: temp, hum, pressure and VOC
    • BSEC software from Bosch has to run on your MCU but takes all parameters (including pressure) into its calculations and has some nice extra things like flags for burn-in and run-in periods, information about accuracy of IAQ data, etc
    • lower power consumption making it possible to run on batteries (90uA average in ultra low power mode gas measurement with update every 5mns)
    • voltage range a bit wider (1.7-3.6V instead of 1.8-3.3V)
    • as a chip it's only a bit more expensive than CCS811, as it's all included it is cheaper than CCS811 + TH + pressure
    • last but not least much more detailed information in datasheet about the calibration process and the precision/accuracy of gas measurements, the max deviation over lifetime of the sensor (10 years !), etc etc while datasheet of CCS811 is completely mute about that. Certified accuracy on one side, no information on the other side, how can you trust the data given by CCS811 ?

  • Mod

    In fact I was also looking at the bme680, that's why I was seeking advice


  • Hardware Contributor

    @gohan said in Air quality node:

    In fact I was also looking at the bme680, that's why I was seeking advice

    If you find more info on CS811 accuracy somewhere (they might have other documents) I'm interested.


  • Mod

    not even adafruit have specs on the sensors

    https://cdn-learn.adafruit.com/assets/assets/000/044/636/original/CCS811_DS000459_2-00-1098798.pdf?1501602769

    If have read correctly it would need to be calibrated against a knows source otherwise it is just good to show trends



  • For what i's worth:

    I've not heard of the BME680 but about a year ago I connected a CCS811 to a RasPi.
    I found the readings from the CCS811 less than useful 😞

    At startup it a assumed the air was "clean" It had an algorithm that tried to extract VOC information from their environment sensitive thin film device. You can read all this is their documentation.

    Another note: It required clock stretching on the I2C interface. On the Pi I found a software library that provided a clock stretching capability. The built in I2C would not work reliably. The need for clock stretching came from the CCS811 tech rep. His statement was: "...Can you please check if the processor you are using supports clock stretching and if so please enable this....."


  • Mod

    Another nail on the CCS811's coffin



  • @nca78 said in Air quality node:

    BME680.

    I just purchased a BME680 from "alice1101983" on ebay for $16.85. I figure by the time I receive it I may be ready to start in on a VOC project again.

    BTW the only reason I mentioned alice1101983 is that I've purchased a number of these types of break out boards from this supplier and all the item i received were what I expected and shipped within a reasonable time.

    BTW I do believe all (most) of the breakout boards are mfg by 1 or 2 factories and the folks we see on ebay are small time sellers.


  • Hardware Contributor

    @johnrob said in Air quality node:

    @nca78 said in Air quality node:

    BME680.

    I just purchased a BME680 from "alice1101983" on ebay for $16.85. I figure by the time I receive it I may be ready to start in on a VOC project again.

    BTW the only reason I mentioned alice1101983 is that I've purchased a number of these types of break out boards from this supplier and all the item i received were what I expected and shipped within a reasonable time.

    BTW I do believe all (most) of the breakout boards are mfg by 1 or 2 factories and the folks we see on ebay are small time sellers.

    Yes there are not so many factories that why most of the shops have similar prices and exactly the same boards.
    I bought a BME680 from Arrow, without breakout board. I still have to make a PCB for it, but I need to finish my tests with PM sensors before I make one.


 

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