Air pollution monitoring

[PeterW]

1 hour ago, billt said:

....peaks when starting are usually less than the particulates I get when roasting coffee....

 

C’mon, let’s see this coffee roaster ..! 

 

BuildHub coffee anyone ...???

[SteamyTea]

Where is the monitor in relation to the wood burner?

 

I had a little play with my plantower, could not get much sense out of it, but then I have never played with serial ports on a RPi.  So down to me I think.

[billt]

[billt]

The sensor is at the same level as the boiler about 10M away. Most of the particulate peak will be due to spill from the fire box door.

[Jeremy Harris]

Sounds like the flue is doing a very good job of ejecting the flue gases high into the air.  Good news in terms of keeping the levels down in and around your house.

 

I wonder how long it takes for the the particulates to fall out of the plume and drift back towards ground level?

 

Quite a long time, I would guess, so they may not get down to ground level until some distance down wind.

[SteamyTea]

@JSHarris

Have you managed to get your monitor hooked up yet?

 

I have just cooked myself one of those 'builder's breakfats', would have been fun to see the readings.

15 minutes ago, billt said:

The sensor is at the same level as the boiler about 10M away

Wish I had 10m in any direction in my house, though 10m from the kitchen is my diesel car

Edited February 10, 2018 by SteamyTea

[Jeremy Harris]

1 minute ago, SteamyTea said:

@JSHarris

Have you managed to get your monitor hooked up yet?

 

 

Not yet, I've been busy digging and getting very muddy this week............

 

I may get some time to play with it this weekend though, with luck.

[DenkiJidousha]

(Ended up with a double post somehow)

Edited March 12, 2018 by DenkiJidousha
Double post

[DenkiJidousha]

Here's another IOT style air pollution monitoring effort based in Germany,

https://luftdaten.info/en/home-en/

 

They have a few UK contributors on the map:

http://stuttgart.maps.luftdaten.info/#6/54.635/-1.782

 

Their sensor build page is currently only in German, Dutch, French, but lists the sensors used:

https://luftdaten.info/feinstaubsensor-bauen/

 

SDS011 fine particle sensor (formerly PPD42NS)

DHT22, temperature & humidity (optional)

 

Update, from their FAQ using Google's translation:

 

Until September 2016 we used the SHINYEI PPD42NS sensor. This uses the optical measuring method and a heating resistor.

Currently we use the NOVA SDS011 as a fine particle sensor. It has the digital outputs for PM10 and PM2.5. This uses the optical measuring method with a built-in fan.

 

Update, Found their English build page which include lots of photos and the wiring diagram:

https://luftdaten.info/en/construction-manual/

 

And another set of English instructions on this blog post:

https://www.byteyourlife.com/en/household-tools/particulate-matter-sensor-controller-project-luftdaten-info/7204

 

Update, while looking for anything in English, I found a Belgian project using the Luftdaten approach as a basis:

http://influencair.be/build-your-sensor/

 

Update, and this spin off group in Bulgaria,

https://en.airbg.info/how-to/

Edited March 12, 2018 by DenkiJidousha
Adding another link, found English build instructions

[Jeremy Harris]

I've got as far as testing the PMS5003 sensor and obtaining data from it for three particulate sizes, PM1.0, PM2.5 and PM10, in units of µg/m³.  Not hard to do at the hardware/firmware level.  I got caught out by buying some fake temperature/humidity/pressure sensors from a well-known auction site (supposedly BME280's, but in reality they were just junk) and am awaiting the arrival of some new temperature/humidity sensors.  One lesson I learned was that the BME280 is not easy to work with, as it needs a lot of 32 bit math to correct the raw data to anything meaningful, and that's not at all easy when using an 8 bit microcontroller!

 

I can recommend the PMS5003 as a particulate sensor, though, as it's very easy to use indeed.  It outputs 32 bytes of data, including a two byte identifier, two bytes indicating the length of the data burst (which seems fixed at 28 bytes of data), 28 bytes of data for each parameter, in the format high byte then low byte, to form each 16 bit data word, then finishes off with two check bytes.

 

I'm just reading the three atmospheric monitoring data words, data 4 to data 6, that give PM1.0 to PM10 data in µg/m³, as that's all that I think I really need.

[SteamyTea]

3 hours ago, JSHarris said:

It outputs 32 bytes of data, including a two byte identifier, two bytes indicating the length of the data burst (which seems fixed at 28 bytes of data), 28 bytes of data for each parameter, in the format high byte then low byte, to form each 16 bit data word, then finishes off with two check bytes.

You will have to explain that a bit more once I have mine connected up again.

I was getting some data, but had know idea what it actually was.

 

Are you going to pop id down the local pizza place in Salisbury and see what it reads

[Jeremy Harris]

4 hours ago, SteamyTea said:

You will have to explain that a bit more once I have mine connected up again.

I was getting some data, but had know idea what it actually was.

 

Are you going to pop id down the local pizza place in Salisbury and see what it reads

 

Funny old thing but I walk through The Maltings at least once or twice a week, and we've eaten in Zizzi's a few times.  My gut feeling is that it had nothing to do with Zizzi's at all, but was a fairly volatile agent that was dispensed locally to where they were sitting.  If I had to guess, then I'd say it's almost certainly not VX, but might well be something like sarin or soman, as both are volatile enough to have been inhaled by the emergency personnel affected and match the symptoms pretty well, particularly the reports of the officers with itching eyes and wheezing, that's pretty classic low dose sarin symptoms, with the chest muscles just starting to misfunction and some effect on exposed mucus membranes.  Fits with the seized hand positions reported and the vomiting, too.

 

Getting back to the sensor, the key is to look for the first two unique start bytes, in ASCII these are B and M.  The two bytes after that can be ignored, as they are the length of the data burst and always add up to 28, and the six bytes after that can be ignored as they are the CF-1 protocol measurements for us in industrial environments.  The next six bytes are the ones you want, and are, in order:

 

high byte for PM1.0

low byte for PM1.0

high byte for PM2.5

low byte for PM2.5

high byte for PM10

low byte for PM10

 

If stored in the right order as adjacent bytes no math is needed as the bytes can be concatenated directly to three 16 bit words, one for PM1.0, the next for PM2.5, and the last for PM10, all reading directly in µg/m³.

 

[SteamyTea]

I may have a go with it tomorrow.  Just been playing the ESP2866 today.

A few quirky issues, but more to do with not having a proper internet connection, which means I can't access NTP data for a timestamp, and just can't seem to get a DS1303/3231 to play at all.

[Jeremy Harris]

For info, here's my post on the Picaxe forum with the initial test code that just squirts the PM data out to  the terminal, although that code may not be relevant to something like Python: http://www.picaxeforum.co.uk/showthread.php?30605-Particulate-sensor-interface-to-any-Picaxe

[Andyman]

Just stumbled across this thread. I’m working on something very similar so will be keeping an eye on your progress!

 

My plan is to use a raspberry pi zero in a IP rated case/box of some description. I’ll use cable glands and hose to draw air into the sensors. I’ve sourced a USB Power bank (~21ah I think) that supports pass through mode so combining this with a 20w solar panel should give me a good few days of running if not weeks in summer

 

I think I’ll need some ducting / manifold 3D printing to connect the hoses to the sensors for both inlet and exhaust.

 

Ive ordered the PMS7003 but still on the hunt for a NOX sensor / temperature and humidity.

 

Not sure about communication yet but for initial testing outside my house WiFi should be fine but might opt for 3G for deployment elsewhere. 

 

Cheers

Andy

[Jeremy Harris]

Welcome Andy,

 

I considered using a RPi, but it's a real power hog, and as I want to power the remote sensor using a battery and solar panel, ruled it out just on that basis.  Half an amp or more to keep a RPi ticking over versus less than 1mA for a PIC, made the decision for me a no-brainer.  I'm probably going to store data locally in the unit, either on a µSD card or USB stick, as well as transmit data back to the house using an HC-12 433MHz transceiver.  These have very good performance and offer better range than wifi,especially if run at low baud rates. 

 

Not sure yet what to do with the data at the house end, that may end up using a RPi or probably a PiZero, running a small display and maybe talking to the house LAN.

 

The only reasonable NOX sensor  I could find was the MICS 2714 (https://sgx.cdistore.com/datasheets/sgx/1107-Datasheet-MiCS-2714.pdf )  I'm currently playing with it, but like the PMS5003 it's a bit of a power hog, so I'll probably end up switching the sensors off between samples, to save power.  My experience with solar powered external sensors is that power budget management is paramount, as it's not at all uncommon to have several cloudy days in a row (a bit like today) that results in very little battery charging.  Battery capacity needs to be enough to run the unit for around 100 to 120 hours without charge, and the charging capacity needs to be able to deliver around 5 to 8 times the device energy use, just to ensure reliability.

 

The BME280 is a pig of a thing to use, because of the relatively complex 32 bit maths needed to post-process the raw data and get something meaningful, so instead I've settled on using the SI7021 https://www.silabs.com/documents/public/data-sheets/Si7021-A20.pdf for the temperature and humidity measurement. 

[SteamyTea]

3 hours ago, JSHarris said:

The BME280 is a pig of a thing to use,

Not on the RPi or ESP2866 it isn't.

Eentually found out what was wrong with my original BME, they were just that temp and pressure, no RH.

[Jeremy Harris]

4 minutes ago, SteamyTea said:

Not on the RPi or ESP2866 it isn't.

Eentually found out what was wrong with my original BME, they were just that temp and pressure, no RH.

 

 

I've heard there are a lot of fake BME280s around, most seem to be really clones of the BMP280 being mis-sold (the BMP280 is the pressure and temperature only device).  The ones I bought were clearly Chinese fakes - wrong package shape and size, wrong markings, plus some errors in the calibration constants.

[SteamyTea]

I am about to start a new thread about home monitoring as I have an idea.

[DenkiJidousha]

Yet another community based IOT air pollution sensor project, http://www.hackair.eu/hackair-home-v2/ - Air quality sensor: Nova PM SDS011, Temperature and humidity sensor: DHT22, Microcontroller: Wemos D1 mini (based on an earlier iteration using an Arduino). They upload data every 10 minutes, and have public maps online at https://platform.hackair.eu/ - looks like a scattering over England and Wales, but none in Scotland so far.

 

They also have a hackAIR portable design, which can be built with SEN0177, SDS011 or PPD42 particle sensors. The code is on GitHub at https://github.com/hackair-project/hackAir-Arduino and  https://github.com/hackair-project/hackAIR-PSoC and they have lots of reports at http://www.hackair.eu/deliverables/ (presumably mandated by their EU funding?) including some information on testing the particle sensors.