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  • JBeale's Avatar
    09-14-2020, 03:43 PM
    FWIW, apparently my PMS5003 sensor (also used in the "PurpleAir" monitor) yields numbers around 2x higher than the official EPA PM2.5 values for woodsmoke particulates specifically:...
    11 replies | 391 view(s)
  • JBeale's Avatar
    09-14-2020, 12:35 AM
    Interesting to see how things change over time, with the sensor in one location in the living room. Inside reading peaked this morning near 300 around 5 am. If I had a continuously running outside one as well, I guess...
    11 replies | 391 view(s)
  • JBeale's Avatar
    09-13-2020, 12:51 AM
    Using a T4.1 with its handy built-in SD card holder, I made a data-logging version in a cardboard box, and it went on a trip in the car to DG's ("doting grandma") place and back, and sure enough there is a reason that...
    11 replies | 391 view(s)
  • JBeale's Avatar
    09-12-2020, 07:13 PM
    You show a very nice setup and some great data! Right now I'm making a portable logging setup with another Teensy and PMS5003 to compare readings at my place with my mother-in-law's. We have a HEPA filter unit on order,...
    11 replies | 391 view(s)
  • JBeale's Avatar
    09-12-2020, 04:25 PM
    Happily it's cold and foggy just south of Portland right now, which is helping slow the fires. Looking at the satellite map, changing winds are pushing the brownest-looking smoke more into western WA, than OR where...
    11 replies | 391 view(s)
  • JBeale's Avatar
    09-12-2020, 05:30 AM
    Photo shows a T3.1 hooked up to a Plantower PMS5003 air quality particulate sensor https://aqicn.org/sensor/pms5003-7003/ and a small OLED display to graph the reading vs time. I had it inside, took it outside briefly...
    11 replies | 391 view(s)
  • JBeale's Avatar
    08-06-2020, 06:02 AM
    Teensy 4.x are more powerful but Teensy 3.x have lower noise ADCs, due to the usual design tradeoffs about processor speed and high-current switching noise. When I first got a Teensy 3.0 this forum didn't yet exist,...
    35 replies | 829 view(s)
  • JBeale's Avatar
    08-02-2020, 06:35 AM
    Well, I am cherry-picking the best few hours I've seen so far, but the concrete block is pretty effective in slowing down temperature changes. It appears to me if I had a high-resolution temperature sensor, and the...
    31 replies | 1720 view(s)
  • JBeale's Avatar
    08-01-2020, 04:13 PM
    After a few days of sitting in a concrete block, which is in turn inside a large styrofoam box, the T4.1 temperature and frequency drift has mostly stabilized. Its reported CPU temperature is around 61.2 C and the...
    31 replies | 1720 view(s)
  • JBeale's Avatar
    07-30-2020, 06:07 PM
    With more data, I see my wild surmise about my GPSDO was wrong, and your more obvious suggestion was correct. Almost all the variation I saw was explained by air movement over the T4.1 PCB, as well as the ambient...
    31 replies | 1720 view(s)
  • JBeale's Avatar
    07-30-2020, 07:18 AM
    I have done no investigation yet, so I certainly don't know the cause of that behavior. Normally you expect a GPSDO to be much more stable than a simple SMT oscillator that isn't even temperature stabilized. I'd expect...
    31 replies | 1720 view(s)
  • JBeale's Avatar
    07-30-2020, 05:41 AM
    Thank you for that reply. Plotting the drift and chi-sq values over two hours, I see the drift is nothing like the random-walk noise I expected. Instead it is dominated by sudden dramatic shifts, as if my GPSDO has far...
    31 replies | 1720 view(s)
  • JBeale's Avatar
    07-30-2020, 04:10 AM
    I've got a start, at least. The code runs on my T4.1, and ping to it from another host shows a smaller RTT than anything else on my LAN (avg = 0.186 msec). I have a Trimble 57964-80 GPSDO with roof antenna, providing a...
    31 replies | 1720 view(s)
  • JBeale's Avatar
    07-29-2020, 01:52 AM
    Is it correct to say that this code acts as a PTP server only, and not a client? For example, if I have two T4.1 boards and I want board #2 to receive time over a LAN from board #1 and blink a LED at the exact top of...
    31 replies | 1720 view(s)
  • JBeale's Avatar
    07-29-2020, 01:30 AM
    A good implementation of PTP "should" be able to achieve sub-microsecond timing synchronization over a LAN. Agilent said in 2005 their experience with PTP / IEEE1588 is ~ 0.1 microsecond accuracy with a lightly loaded...
    7 replies | 381 view(s)
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PM2.5 air quality monitor - Oregon fires 09-14-2020 03:43 PM
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10-25-2012