Thread: Developments in Dust Sensor tech

Hi Bob, I downloaded this PDF in English for the PMS7003, data protocol is simple and I could easily program a small micro to decode and drive an LCD and add USB data out for a PC capture, can also write a program for Windows PC to display it.

Don't know if there is more info in this PDF or not but needs your knowledge to see if it is indeed worth using something like this. - Mike.

http://www.brisdance.com/Wood/PDF/PMS7003Sensor.pdf

Just a follow up on these sensors.

The sensors referred to above are aimed at general air quality (all dust) so they are usually designed to operate in the 1 to 1000 ug/m^3 (micrograms/cubic metre) range (0.001 to 1 mg/m^3, milligrams per cubic metre, also sometimes abbreviated to ppm). Their low level sensitivity, accuracy and resolution varies considerably - as stated above some have accuracies and resolution of around +/- 15% but that does not matter so much for WW as we tend to operate at the higher end or beyond the scales of these sneers.

Thaw sensors are designed to specifically measure PM2.5 dust (dust less than 2.5 microns in size - well between ~0.3 microns to ~ 2.5 microns) which is considered the dust most likely to impact on human health.
Some of the sensors do provide information about other size ranges which is useful for WW dust measurements. The standard Dylos meter is one such example, although at 10+ times the price of the other sensor it will eventually face stiff competition from the newer sensors. The big advantage of the Dylos at the moment is the very limited software available for the newer sensors.

There is a very interesting real-time world-wide air quality monitoring system on the web (Worldwide Air Quality ) that monitors PM2.5.
It is very interesting to see where Australia sits.
Note that coastal stations are likely to be affected by ocean generated aerosols which might not be all bad.
If you click on any one location you can access all manner of logged data from that place.

The PM2.5 data shown are known as "Air Quality index" (AQI) data

Green or "good" is less than 0.05ppm
Yellow = "Moderate" is between 0.05 and 0.1 ppm
Orange = "Unhealthy of sensitive groups" is between 0.1 and 0.15 ppm
Red = "Unhealthy" is between 0.015 and 0.3 ppm
Purple = "Very unhealthy" is between 0.3 and 0.4 ppm
Brown - above about 0.4 ppm is considered "Hazardous"
Effects on Health etc are listed here Air Quality Index Scale and Color Legend

The current Australian OHS limits for wood dust are 1 ppm for hardwoods, 5 ppm for soft woods and 0.5 ppm for MDF.
The first two are based entirely on a UK standard from the 1970's and there has been no research on Aussie woods, the MDF value is from a few years ago.
Bear in mind these OHS limits covers ALL particle sizes so 1ppm of wood dust may only contain 0.01 ppm of PM2.5
The reverse is unlikely, i.e. if you are working with pine and such a sensor reads 0.5 ppm then it is most unlikely that there is zero dust in the other particle size ranges.

When I get the Sonoff sensor I will check its output against a full count particle counter to see how this translates to working with real wood.

One unknown about these sensors is can they run continuously and handle the high dust loads as might be found in a woodworkers shed?
Experiments have been done on some sensors and they seem to be able to cope with moderate general dust exposure but eventually need dismantling and cleaning.
Long term continuous operation will also compromise the sensor elements and after a couple of years they lose sensitivity/calibration and cannot be used reliably.
However. given how cheap they are that might be not be than much of a problem
What this means in practice for Woodworkers is these sensors may be better used for short term testing such as setting up a new shed or DC or investigating the dust making/capture regarding a new process or tool.

More to come when I get the Sonoff

Originally Posted by MandJ

Hi Bob, I downloaded this PDF in English for the PMS7003, data protocol is simple and I could easily program a small micro to decode and drive an LCD and add USB data out for a PC capture, can also write a program for Windows PC to display it.

Don't know if there is more info in this PDF or not but needs your knowledge to see if it is indeed worth using something like this. - Mike.
http://www.brisdance.com/Wood/PDF/PMS7003Sensor.pdf

That's the same PDF I linked to - I can see the first couple of images but not the rest, and the text is scrambled in places after that.

Its definitely worth pursuing and f you can knock something up that would be excellent.
I was going to corral my son to do this but he is flat out dealing with the latest worm at work and all I see/hear of him when I visit is the back of his head and a few grunts.
I can offer to test it against a real particle counter inside a wood working shed.

As I said in my recent post the trick with these sensors for use in a workshop is to see how well their output translates to real wood dust loads.

The Sonoff that is arriving soon uses a Sharp sensor which the Sonoff people describe as a "toy" sensor.
It only measures PM2.5 but for around US$30 delivered including the mobil App I want to see what it can do.
The 7003 has the advantage that it does PM1.0, PM2.5 and PM10 which would be worth knowing.

Originally Posted by BobL

Following a tip from RayG I have ordered a Sonoff device that uses the Sharp sensor and outputs to a mobile phone app, just to have a play with (Sonoff wifi controller https://www.itead.cc/smart-home/sonoff-pow.html). As far a WW dust goes, the Sonos is likely to only have three dust level settings brown, yellow and green which translates to "OK - warning - Not OK" and I will calibrate this against the particle counter from work. The Sonos provides no particulate size info but most WW'ers are probably not that interested in that info anyway and would just like a single number to play with.

The Sonoff SC sensor arrived last week and I have a had a bit of a play with it.

From their website;

Sonoff SC is an ESP8266 based WiFi environmental monitor device. It detects current temperature, humidity, light intensity, air quality, and even sound levels, and directly send realtime data to iOS/Android APP EWeLink

and the website also warns "This is more a TOY than a final product. Please take it as a product for hobbyist"

As you can see below you only get actual numbers for the Humidity and Temperature readouts - the others only have 3 levels.
The unit can be used as a sensor to control remote power switches via Wifi so it can be used to start a fan, heater, alarm or a light source.
This is what RayG has done with his to control humidity in a shed but I won't discuss any of the non-dust sensors here.

EWeLink.jpg
I knew these limitations before I purchased - I just wanted to see what it could do in terms of dust levels.

This is it out of the box - it's small, about 100 mm high.
IMG_2204.jpg
Air drifts down from the top through what looks like a speaker grille and the main exit is through that slot in the bottom.

On the back there are these 3 things
The SD slot does not function, the button marked "audio" is the Wifi pairing button and the third is a micro USB connection.
IMG_2205.jpg

The setup was straightforward. There are no instructions in the box, there's just the Sonoff unit and a switched USB power cable.
Instructions, the app etc are all on-line.

The actual setup is quick once you get the gist of the "Chinglese" and can bel done via the app which has some instructions built in, but I found using the website easier to follow.
I had to swap Wifi networks in the middle of the setup which required complete erasure of the old setup before I could setup the new connection.

The dust sensor itself is a GP2Y1010AU0F Sharp dust sensor that is smaller than a matchbox.
Inside the Sonoff, the small entrance in the side of the sensor into which dust has to pass is oriented at right angles to the vertical.
This has almost certainly been done deliberately so it's not flooded wth too much dust which could easily ruin it.
Hence it relies on plain old diffusion so only fine dust can reach the sensor.

Waving a burning incense stick in front of the top of the sensor does not initially do anything as the smoke/dust is hot and rises away from the opening
Eventually as more of the room fills with smoke it will triggers the sensor but it took many minutes to do this.
The same thing will happen with fine dust so a way of directing dusty air into the sensor is needed.

To do this I set up a plastic box and a 12V PC fan like this.
The unit does not need to be perfectly sealed as you don't really want a gale of air flowing through the Sonoff itself or it will fill up with dust.

Now placing a burning incense stick in front of the grille triggers the sensor straight to "unhealthy" in about 3 seconds.

IMG_2208.jpg

To quickly test the sensor and not fill my shed up with too much dust I adapted my son's home made 3D printer thermal stabilisation enclosure to use as a dust chamber.

The black cable inside the enclosure is the USB PS cable for the Sonoff and the white cable is for the 12V fan.
IMG_2209.jpg

The side of the enclosure can be folded down as shown below and a small amount of dust injected at the hole shown by the red arrow.
With the fan in the plastic box running, a burning incense stick poked through the hole triggers the sensor in about 5 seconds.

I have also tried it out with an ROS sander.
Using the internal fan in the sander to inject mdf dust into the chamber will trigger the sensor in a couple of seconds.
Even the residual dust coming off the sander (i.e. not touching wood) triggers the sensor to "moderate" in a few seconds

IMG_2210.jpg

The bottom line is, what do the 3 levels of air quality "Good", "moderate" and "unhealthy" mean in terms of dust levels?
If I get some time I will hopefully access a particle counter this week and we'll find out what they are.

The nominal Voltage response of the Sensor itself is known and is as follows.
It's range of measurement is very small i.e. between zero and ~0.5 mg/m^3 (the OHS threshold for MDF).
I reckon the air quality setting of "good" will be < than ~1V, "moderate" will be between 1 and 3.5 and "unhealthy" will be <3.5V

However, it is supposed to be a PM2.5 sensor so it only measures <2.5 micron dust.



Usually 0.5 mg/m^3 or ppm of PM2.5 will mean a considerably greater total dust load but it will be interesting to calibrate it against a real particle counter.
For example in the floor sweeping tests I did, PM2.5 was around 10% of the total dust load so a 0.5 ppm PM 2.5 load would be around 5 ppm total dust.
It will also be different for different woods and processes but I will take a look at that and see just how variable it is.
Despite all these problems, given these things only cost US$20, it could be a " better than nothing" sensor for DIYer on a tight budget.

If you decide to rush out a buy one just remember, these things will DIE VERY quickly if they are exposed to too much dust. Do not for example put them in front of the dust output of a power tool or even next to an un-ducted WW machine like a lathe.

If it does provide a reasonable indication of dust levels. the way I envisage something like this being used in a shed is that it is placed upside down, at head height somewhere nearby but such that it doesn't cope a full spray of wood dust.
While performing a dusty task you turn it on and it will trigger an alarm to tell you what you have done in the last few minutes is too dusty and you should think about what you have done and do something about it in future. You could then also run an exhaust fan and see how long it took to come back to healthy.

The speed of response will be determined by if you decide to add a fan or not.

I strongly suspect that if you want the unit to last you would need to use it on an "as needed basis" because if you leave it on 24/7 for a few months it most certainly will fill up with dust and die. The sensor itself costs about the same amount as the whole Sonoff so is not worth replacing. I think installing the Sonoff upside down will help ensure that only really fine dust gets into the sensor.

If it works out to be useful I will leave mine running 24/7 to see how long it lasts. My son will test the Wifi security aspect of the Sonoff at some stage or other

The other sensor I have ordered (PMS 7003) should arrive soon and should be much more informative but of course at this stage it also requires much more development.

Their even getting school kids involved.

https://www3.epa.gov/airnow/teachers...structions.pdf

Originally Posted by BobL

If it works out to be useful I will leave mine running 24/7 to see how long it lasts. My son will test the Wifi security aspect of the Sonoff at some stage or other

The other sensor I have ordered (PMS 7003) should arrive soon and should be much more informative but of course at this stage it also requires much more development.

Thanks Bob, very interesting, I've now got two Sonoff SC's in the workshop logging temperature and humidity, and comparing with a weather station, the humidity values from the sonoff aren't very accurate. Neither were the temperatures before uprading to the DHT-22.

As far as the wifi goes, the chip is the ESP8266, and is a brilliant device for embedded connectivity. I've reflashed it with the TASMOTA firmware https://github.com/arendst/Sonoff-Tasmota and use MQTT and node red for control logic.

The dust sensor is driven by the Atmel not the ESP8266, although god only knows why they put an extra cpu into the mix, so if you want to change the dust sensing you have to reflash the Atmel.

For the display stuff I'm using grafana https://grafana.com/

OK I have done some preliminary tests by exposing the Sonoff to dust from ROS sanding of MDF and comparing the Sonoff with a proper particle counter, and as I expected it has a very narrow measuring range.

I did the test 3 times with variable sanding times (3, 5 and 7 seconds) and got consistent results which was something.

In terms of PM2.5 dust, my Sonoff switched from "good" to "moderate" at around a 0.3 ppm and from "moderate to "unhealthy" at around 0.6 ppm. This is more or less where I expected it to switch for this size range of particles.

In terms of "total dust" the Sonoff effectively switches from "good" to "moderate" at around a 1.5 ppm and from "moderate to "unhealthy" at around 9 ppm.
The Sonoff doesn't measure all particles but the other particle counter can so that's how I measure the dust levels

As a reminder the OHS limit for total dust is 1 ppm for hardwoods and 5 ppm for softwoods.
Naturally it doesn't mean that for hardwood dust exposure you are totally safe at a 0.99 ppm and totally unsafe at 1.01ppm of dust.

This means the Sonoff maybe suitable be used as a basic indicator for softwood dust - if you maintained your shed in the "good" range you should be below OHS limits for softwood, and close to but just over the OHS limits for hardwood.
The Moderate range is borderline for softwood and well over for hardwood dust.
The "Unhealthy" range display on the Sonoff is definitely unhealthy for both woods.
Even the good range may not be good enough for MDF (OHS total limit of 0.5 ppm)

As I said in another post above the Sonoff is designed as a PM2.5 detector (smoke, smog etc) so it doesn't measure bigger dust particles. The reason for this is designed to be used indoors in homes so it it assumes the big bits of dust have well and truly fallen out of the air and just don't make it inside a home. However, there are situations in wood working where a very large volume of intermediate size (3 - 12 micron) wood dust is formed but it is not accompanied by a corresponding amount of the PM25 particles.

If an operator is close by dust sources (e.g. turner, or just running a thicknesser of table saw) the operator can experience high loads of these larger dust particles. The particle sizes have been implicated in nose and throat cancers but the Sonoff wont detect those particles and so might still give a "good" reading.

Clear a mud? errr . . . . dust. I will have to do more testing.

Originally Posted by Lappa

Their even getting school kids involved.

https://www3.epa.gov/airnow/teachers...structions.pdf

Bookmarked and saved the pdf. The hard part is going to be finding a kid to make it.

Pete

This morning's Health Report on the ABC had an item in there regarding air pollution and I chased it up on the web.

A large (~30) team of epidemiological experts with funding from the Gates foundation has completed and published a massive worldwide study on the impact of air pollution in human health.

The result is that air pollution has been moved from the 8th leading cause of death to the 5th leading cause of death.
The particles that were focused on were PM2.5 since these travel further across countries and can get into peoples homes.
It has also found that not just lungs are affected but heart disease and stroke are right up there.

The full article can be found here http://thelancet.com/journals/lancet...505-6/abstract

These findings have significant relevance for wood workers.
Up until now it's been the 20 - 5 micron wood particles that have been specifically identified as causes of nose and throat cancers in wood workers.
The smaller particles were thought to cause something but the experts were not really sure what they did.
The mechanism by PM2.5 particles are responsible for deaths is still not clear but the type of particle seems to be irrelevant so "general over inflammation" of body systems is being investigated because PM2.5 micron particles can more easily invade and irritate the body. I'm no health expert and this is about as far as I can go with this.

This highlights the need for wood workers to pay particular care with fine dust and get that fine dust out of their shed. Some inexpensive way of monitoring PM2.5 would also help.

Not sure if you have seen this or if it is of any interest.

Comparative measurement of Dylos - PMS 7003 and others. Half way down the page.

Sensing the Air Quality: Research on Air Quality Sensors


BTW if you hover over the Sensor heading the graph will highlight the sensor readings.

Originally Posted by MandJ

Not sure if you have seen this or if it is of any interest.
Comparative measurement of Dylos - PMS 7003 and others. Half way down the page.
Sensing the Air Quality: Research on Air Quality Sensors
BTW if you hover over the Sensor heading the graph will highlight the sensor readings.

Yep have read that one - it's part of the world wide air quality monitoring site I referred to in my first post.

There's rapid developments happening with these sensors as we speak so I expect the gap between a professional particle counting system such as Air Quality Monitoring Stations - Product Overview (e.g. ~$10k) , and a reliable consumer based product to shrink and eventually become available for under AUS$100.

The price of the PMS7003 is US$27 (Shipping was $1), the photon micro controller with WiFi to drive it is US$40 (half that is shipping!) and that comes with a mobile app to configure and drive the controller. There's some open source basic software available but it "needs some work".

I did some hardware costing with my son this morning for a PM 2.5 particle sensor/basic non-wifi controller/minimum character display to display actual ppm dust numbers, and it could be as low as as AUS$50.

Thanks Bob, again if this unit turns out to be useful in the WW workshop then I'll likely get one down the track. Lots of ways to connect these things. I've got a spare 32 bit micro and 7" LCD colour screen that's just gathering dust, so I might program that for display and graphing via a radio link from the sensor. Looking forward to the results when you get the sensor.

Cheers.

Originally Posted by BobL

In terms of PM2.5 [MDF] dust, my Sonoff switched from "good" to "moderate" at around a 0.3 ppm and from "moderate to "unhealthy" at around 0.6 ppm. This is more or less where I expected it to switch for this size range of particles.
In terms of "total MDF dust" the Sonoff effectively switches from "good" to "moderate" at around a 1.5 ppm and from "moderate to "unhealthy" at around 9 ppm.

I repeated the test this time using burning incense as the dust source.
The resulting dust is nearly all less than 5 microns so the switching points for total dust and the PM2.5 dust levels should be much closer

This time, in terms of PM2.5 dust, the Sonoff switched from "good" to "moderate" at around a 0.08 ppm and from "moderate to "unhealthy" at around 0.2 ppm.

In terms of "total dust" the Sonoff effectively switches from "good" to "moderate" at around a 0.1 ppm and from "moderate to "unhealthy" at around 0.25 ppm.

The switching points are closer but then again they are also considerably lower. Based on these results the Sonoff would appear to be be too sensitive for wood dust detection.
Nevertheless we are not burning incense so I will keep testing this time with hardwood.

Well, perhaps as to be expected, the hardwood behaves more like the MDF than incense.

In terms of PM2.5 dust, "good" to "moderate" switches at around a 0.25 ppm (0.3 ppm for MDF) and from "moderate to "unhealthy" at around 0.5 ppm (0.6 ppm for MDF).

In terms of "total dust", from "good" to "moderate" is at round 1.2 ppm (1.5 ppm for MDF) and from "moderate to "unhealthy" at around 4 ppm (9ppm for MDF).