[aprssig] APRS Air Quality Monitoring

KF4LVZ aprssigZbr6 at acarver.net
Sun Nov 11 20:35:29 EST 2018

You can scale the output by changing the airflow.  Swap the fan out for
something with 10x the flow (as small diaphragm vacuum pump with
throttle valve so you can tune it) and the 0-999 will actually be
0-9990.  It reduces the resolution by 10x but you'll have your range.
Just put a filter in front of the vacuum pump to keep the dust from
fouling the diaphragms and valves.

I've done this at work with commercial detectors to tweak the range as
needed without swapping out for other sense heads (expensive).

The extra air flow will also help reduce the amount of dust settling
inside the detector.

On 2018-11-11 17:19, Scott Miller wrote:
> Let me know if you find anything suitable for a higher range.  Like
> much, much higher.  I've been talking about building nephelometers for
> Burning Man for a few years to help visualize how much dust is kicked up
> by activity (mostly vehicles) out there.  The challenge is making
> something that won't get the optics fouled in an hour - it'd probably
> have to have a continuous flow of clean air past the optics.  It's not
> unusual for visibility to get down to less than 20', and at night
> (backscatter from lights makes it worse) I've seen it down to about 3'.
> At that price, I'll have to give one of those sensors a try for use at
> home.  Apparently fire season is year-round in California now and it's
> always orange outside.
> Scott
> N1VG
> On 11/11/2018 3:41 PM, Steve Dimse wrote:
>>> On Oct 12, 2018, at 12:00 PM, Robert Bruninga <bruninga at usna.edu> wrote:
>>> Has anyone looked into the lower priced air-quality monitors that are
>>> out
>>> there? $50 to $250?
>> Just a followup. I received my SDS011 from China in 10 days, for just
>> over $22 with free shipping via eBay. It is a piece of cake to set up,
>> comes with a naked USB serial dongle and cable. I plugged it into a Pi
>> and with a few minutes of writing code I got it running. It outputs
>> binary data so you can't just open it with a terminal program.
>> My first impression is very positive. The Pi is not on the internet to
>> share live data but here is two hours.
>> http://www1.findu.com/aq.png
>> In this plot I was burning a candle to see if that adversely affected
>> the air quality in the house, it did not. Then I blew the candle out,
>> it smoked for 15 or 20 seconds, and the result is impressive. The
>> sensor is about 5 feet from the candle, and it seems like the original
>> plume of smoke was carried towards the sensor, causing a big spike
>> that quickly resolved. The AC (it is still 85 in the Keys) then
>> distributed the particles throughout the house air volume, and either
>> dilution from window leakage or lung filter have been continuing to
>> decrease it since.
>>> What parameters are available and from that we can define an APRS
>>> format.
>> Go ahead, hopefully as a user-defined format.
>> This sensor reports particulate matter in two sizes: <2.5 and <10
>> microns, in units of tenths of ug/m^3, max is 999.9 and 1999.9
>> respectively (i.e. raw values to 9999 and 19999). Other elements of
>> air quality are O3, CO, SO2, and NO2, but I'm not sure if those are
>> worth adding to the format, perhaps only as options after the PM
>> values as they will be much more expensive to monitor.
>> When you define it I can start sending it right away, though it may be
>> a while before I have a weatherized version to give outside values. I
>> may add findU support too.
>>> We can include radiation counts too...
>> No, that should be on a separate message. Most AQ stations won't be
>> reporting this, keep them separate.
>> Steve K4HG
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