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Air Quality Monitor (CO2, Temp, RH, Pressure, and now, PARTICULATES) ***Drivers attached*** - Page 2 — Parallax Forums

Air Quality Monitor (CO2, Temp, RH, Pressure, and now, PARTICULATES) ***Drivers attached***



  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2022-05-30 19:16

    I'd suggest you add a connection from Prop p6 to DS1307 pin 7, with a high ohms pullup. The 1 second heartbeat from the RTC can be useful.

    That's a nice thought. I'm going to put it off for now, though, until I know for sure that the SPS30 will work well on the I2C bus. If it doesn't, I'll need P6 and P7 for SDA and SCL, so I can use P4 and P5 for serial comms.

    The JST cable, at least, is discrete-wire, rather than closely-abutted ribbon conductors. So crosstalk should be less of an issue. And I'm using 4.7K pull-ups. Still, for a 3.3V Vdd, 3.3K pull-ups would be even better. The original I2C spec that called for 4.7K pull-ups was written for a 5V Vdd. To get the same initial pull-up current at 3.3V, you need 3.3K.


  • Very interesting project I would be interested in buying a couple of them when you are done with all of the revisions on the circuit board

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2022-09-21 02:42

    When recording CO2 measurements, it's helpful to know if people are present, so the measurements can be correlated with human activity, such as breathing. To that end, I installed a motion sensor in one of my CO2 monitors:

    Each record that's saved includes a CO2 reading, temperature, humidity, and a summary of human activity during the recording interval.

    BTW, this unit uses the larger Sparkfun 128x160 display. I did this so I could display the date and time. But I have to say the display has been a disappointment. Both the brightness and viewing angles suffer in comparison to the 128x128 display. I probably won't be using it again.

    With wildfires raging, particulate pollution is of particular concern. So I bought a Sensirion SPS30 particulate sensor. It's a snazzy little unit that bins particulate sizes in PM1.0, PM2.5, PM4.0, and PM10 particulate sizes for both µg/m3 and particle count per cm3. From the PM2.5 and PM10 mass readings, I can compute the EPA air quality index (AQI) and display it on the screen. Here's a photo of unit's guts:

    . . . and of it "fully dressed":

    A lot of programming remains to be done. I need to sequence the display of the various readings (CO2, temp, RH, barometer, AQI, time/date), since they don't all fit on the screen at once.

    I'm happy with the PCB layout now. It encompasses everything I wanted to do with it. I know some of you expressed an interest in obtaining some for your own use. I'm happy to make bare boards available. Of course, to take advantage of time/date, barometer, and extra EEPROM, you'll have to do some surface-mount soldering. If you can live without those features, everything else is thru-hole. Let me know what you think.


  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2022-09-20 22:13

    I've added a driver object for the SPS30 particulate sensor to the top post.

  • Tracy AllenTracy Allen Posts: 6,658
    edited 2022-09-28 23:12

    Hi Phil,
    Please count me in for a couple of those fabs. As usual you've really come through with this, feature by feature, over the past few months!
    -- Tracy

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