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  1. #121
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    I was thinking about how I use the workshop and how sometimes I'm in there for a few hours but not necessarily making dust, there are times where I do an hour of dust making and spend the rest of the day assembling the project, other times I'm only in there once a week.

    The point is that if using a laptop or tablet, you might not want to leave that running 24-7.

    I've found that the dust levels in the workshop are usually lower than outside but as BobL pointed out, outside air pulled into the shed by cross flow ventilation and a running DC can skew the sensor readings, without knowing those cross flow intake levels your readings can be meaningless. Normally my outside and inside air counts are close, but a week ago outside AQI was in the moderate range all day, inside was about a third of the readings, the outside readings were way more than any dust the machines in our workshop produces.

    So having an outside sample is important to ensure your reading are from wood dust. Along with the fact that I don't have the sensors running when I'm not in the WS, I decided to save all long term AQI values for each sensor and reload them at start up, what i end up with is the AQI valid for the period of time that I'm in the workshop. Otherwise in a hobby environment some of us may never get a true picture of AQI levels verses actual workshop time. IMHO Having the sensors logging low levels close to zero for days on end when your not in the work shop only skews readings towards the low end of the AQI scale.

    So with that in mind, the changes have been made. You can manually reset the long term AQI for all sensors to 0 at any time. So what I now have is the long term AQI for them accumulated time that I'm actually in the workshop.

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  3. #122
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    Quote Originally Posted by MandJ View Post
    So having an outside sample is important to ensure your reading are from wood dust. Along with the fact that I don't have the sensors running when I'm not in the WS, I decided to save all long term AQI values for each sensor and reload them at start up, what i end up with is the AQI valid for the period of time that I'm in the workshop. Otherwise in a hobby environment some of us may never get a true picture of AQI levels verses actual workshop time. IMHO Having the sensors logging low levels close to zero for days on end when your not in the work shop only skews readings towards the low end of the AQI scale.
    I agree.

    I set the Mens Shed sensors up so that they did not record anything when the Shed was not open. That's 8:30 - 4:30 M-F (except Thursday mornings). However, even then there are open, there are long periods where there appears to be no dust above back ground level. Part of this is because the sensor located inside the Shed is too high up (2.4m) and too far from the machinery to record anything clearly. This is a problem in a large area shed and I don't trust a sensor to be located anywhere at operator height in the middle of the Mens Shed. I might have to rethink this and see if I can make up a ruggedised container of some kind to house the sensor. Even then It is likely to be bashed by bits of timber etc and because much of the machinery is on wheels and moved around.

    DIY sheds are much easier as you control what is done.

  4. #123
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    Bob your initial findings in the Mens shed saved me a lot of wasted time, and even in a small shed you may need to think about placement, but all that early work you did, and my own testing, made me realise that I needed to measure particle counts as close to the operators head position as possible, if these sensors have proven one thing to me, it's that really good cross flow ventilation is absolutely critical for effective dust removal - I wonder who on the forum has harped on about that very thing?

    A small sensor box with a tiny radio link and battery for at least one sensor is a neat way to go, but would likely be difficult in a Mens shed environment.

  5. #124
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    Quote Originally Posted by MandJ View Post
    . . .if these sensors have proven one thing to me, it's that really good cross flow ventilation is absolutely critical for effective dust removal - I wonder who on the forum has harped on about that very thing?
    The calmest wind speed places in Australia average ~4 km/hr throughout the year.
    This equates to about 1m/s.
    A 0.5 m/s breeze through a 800 x 2100mm shed door moves a lot of air and fine dust (1800CFM) even half that is pretty good.
    One problem is it's not always available in all areas.


    A small sensor box with a tiny radio link and battery for at least one sensor is a neat way to go, but would likely be difficult in a Mens shed environment.
    something to add to the Todo list.

  6. #125
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    I am working on the next sensor setup this time using the smaller PMSA003.

    Two things I have discovered so far.

    1) The fan is supposed to be rotatable by 90º so the inlet and outer can be further separated.
    This is supposed to be done by unscrewing the 2 screws holding the teeny tiny impeller onto the sensor case and rotating the impeller.
    Problem is the wiring inside the sensor does not allow for the rotation - the only way I can see of doing this is taking the sensor case apart so that a plastic tab holding the wiring down can be cut away. Taking the case apart is something I'd rather not do as the case is not screwed together and I would be concerned about snapping the case tabs.

    2) The connection board is wired so if it is used as per the labels stated on the board, the board protrudes past the air inlet and outlet.
    This makes butting/sealing the inlet and outlet hard up against an external box/case rather difficult.

    Here you can see how far the connection board pokes up above the air inlet and outlet.
    The 7003 sensor has the connection board protruding out to the side so it does not get in the way of the air inlets.
    The mm or so of the board that protrudes up above the air inlet and outlet can be sanded away without any problems
    PMSA0034.jpg

    Fortunately the 2 x 5 pin micro plug attached to the board can plug into the 2 x 5 pin sensor socket the other way around.
    Then the connections just need to be reverse compared to what the board labels say. Now the sensor can fit snug up against a box or case.
    PMSA0035.jpg

    The pin layouts are not symmetrical - if the plug int the sensor is reversed then
    Vcc (was purple wire) has to be connected to the green wire
    Grnd ((was orange) has to be connected to the blue wire
    Rx (was Green) to Orange wire
    TX (Was blue) to Purple wire.

  7. #126
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    My Blue Tooth/Wifi modules arrived some time ago but finally felt well enough to get back onto implementing these in a remote dust sensor setup.

    Not that much to see that makes sense, but over on the LHS is a dust sensor and BT slave (circled in red and marked Slave) and on the RHS that range of wires on the benches (Labelled Master) is the BT master connected to a Mega Arduino board with a Real time clock, a temp/humid sensor, SD card and a 20x4 character LCD screen - some closer up pics shown below.

    SMsetup.jpg

    This is the slave end.
    The Blue box marked A and the BT slave module (marked B) will go into a small container along with a battery, which will be attached to a shoulder strap worn by an operator.
    SlaveSensor.jpg

    AT the master control end, the horrible mess (master BT module labelled C) will go into a second box which should be able to sit anywhere in the shed and collect data on an SD card.
    The LCD shows a rolling PM10 Concentration data with every number representing a ~30s average.
    The operator will be free to move around in the shedand do whatever they like.
    Master.jpg

    Setting up and pairing the BT modules was dead easy once I found I good Youtube vid. There was zero programming needed, just removed the dust sensor from the Arduino and replaced the same wires with the Master BT module and wired the SLave BT to the sensor and away it went,

    As usual, turning this jumbled mess into a half decent workable/useable product can be as tricky as getting the circuit and program working.

  8. #127
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    This morning around 9 am I took the dogs for a walk - clear sky, no breathing problems.
    Around 1pm my asthma kicked in and I went outside to see some bushfire smoke starting to rolling in over the city.

    Got a particle counter out and have been monitoring it since.
    This is the highest I've seen so far.

    The PM10 value of 51.6 ppb is ~3 times above the annual average for Perth while the PM2.5 value of 47 ppb is nearly 8 x above the Perth annual average.
    It's not helping my asthma at all - just writing this post has started me coughing.

    Bushfire.jpg

    About 90 minutes later the PM10 reached 117 ppb, half an hour later the and direction changed and it was down to 39 ppb and right now its down to 23 ppb.

    This shows why you have to take readings outside your shed to make sense of the measurements.

  9. #128
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    Normally I just show photo's of my spaghetti tangles but though some of you may be interested to see a sequence of several photos to see how its done and that it is nowhere near as bad as it looks.

    The first photo shows some of the main components installed in the housing.
    I use 3mm brass or nylon standoffs to attach these to the enclosure.

    The box/enclosure doesn't need to be anywhere near this big (especially as larger boxes with a transparent lid cost >$20) but these ones only cost $8 on eBay.
    Anyway it helps in this case so you can see the components and how they go together.

    A is the Arduino micro controller board - power is supplied from the outside of the box to either the Usb (silver) or 12V DC (black) power sockets for which holes are cut into the LHS of the box.

    B is the Bluetooth master (on a non-BT setup this is where the dust sensor goes (same number of pins)

    C is a standard Arduino Humidity/Temperature sensor

    D is the pause run switch that closes the data logging file used prior to removal of the SD - otherwise data is lost

    PMSA003a.jpg

    The next thing that is installed is the red "data shield" board shown in the photo below.
    The data shield contains a Real Time clock and an SD card (E) for which a 2.5mm slot has to be cut into the side of the box to insert/remove cards.
    This data shield plugs into the Arduino board and transfers the sockets from the Arduino board below to to the shield above.
    PMSA003b.jpg

    The dozens of holes in the middle of the board are for custom connections or circuits
    I use two rows of the for the sockets/headers circled in green are added by me - the top row are all joined underneath and are used as a +5V DC rail
    The bottom row are also joined and used as a ground rail.
    These are needed as extra connection points for the sensors and screen etc as they require more +5V and Grnd connections than are available on the Arduino board.

    Below shows the first half of the wiring

    I have mostly used red for +5VDC and Black for Grnd and tried to keep the related connections the same length and close together.

    Green label "a" (red and blue connectors) and "b" (blue, white, yellow and orange) are used to connect the shield to the Arduino for real time clock and SD card operations.

    "c" transfers +5VDC and Grnd from the Arduino/Shield to their respective rails

    PMSA003c.jpg

    "D" toggles either +5V(red) or ground (black) via the yellow connector onto digital port 7 of the Arduino board - depending on the V state of port the program runs or pauses so the SD card can be safely removed.

    B is the BT master and it has a 4 pin (+5V, Ground and two serial lines)
    C is the Temp/Humidity sensor and it has 3 pins (+5V, Ground and a data line (blue wire) that goes to digital socket 7 of the Arduino)

    Next comes the screen and this has 12 connections - I won't show it in this post as its VERY messy.

  10. #129
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    Now I added the display, like I said there are 12 connections so it gets messy.
    I could have made things tidier but I ran out of patience and just wanted to get things working

    I have some "serial" versions of these displays which have only 4 connections but when I have the space I use the up the non-serial versions I still have.

    PMSA0036.jpg

    The matchbox size (metallic blue) PMSA003 dust sensor is in it's own little enclosure and is small enough to ride on an across the shoulder strap or even in a jacket/shirt breast pocket.
    PMSA0037.jpg

    Its powered by a 5V battery that can be worn on an cross the shoulder strap or a waist belt.
    I will get a gender bender to eliminate the need for the long thicker cable
    PMSA0038.jpg

    Display is all working.
    The micro-controller box box sits over by the side of or in a safe play in the shed.
    The numbers displayed are the last 20 readings of PM10 - all data stored on the SD card.
    PMSA0039.jpg

  11. #130
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    Found out something about powering devices using USB/Li Ion batteries after the USB battery powering the remote sensor box kept shutting down.

    At first I thought it might have been drawing too much current so I put an ammeter in between the battery and the particle counter in the small box and noted the current jumped around quite a bit - between zero and about 80 mA but this is nowhere near over current enough to make it turn off and the battery is not even close to getting warm.

    A few timings showed the battery was turning itself off after anywhere between 10 and 60 seconds. Tried another battery - same. Tried a different make of battery, even shorter time - 3 to 10 seconds only with that one.

    After hunting around on the web it turns out USB Li-ion will also turn themselves off if the current drops below a certain value - this can be anywhere from 100 down to 30mA.
    So I inserted an LED with a resistor in series to draw a constant 50mA at all times and now the current jumps around from 50 to 120 mA and the battery stays on - well at least it has stayed on for last 2 hours.

  12. #131
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    Hello,
    I was looking for more info about PMS7003/PMSA003 and I found this very interesting thread
    I would like to develop a low power system based on 7003 or A003 and I would like to choose the sensor with the lowest power consumption.
    Unfortunately datasheets of both products are pretty vague about it. I was wondering if anyone of you had a chance to measure the actual current consumption of such devices.

    Thank you in advance for your reply.

  13. #132
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    The Spec in the datasheet for the PMS7003 is less than 100 mA. My notes show around 60mA for the sensor with no radio or USB serial interface.

  14. #133
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    I get between 27 and 55 mA for the 7003. The A003 should be the same. Next time I take it out of my remote setup I will measure it.

    [EDIT] Just had opportunity to remove the A003 and got the same currents.

  15. #134
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    Here's a pic of my personal/wearable dust sensor.
    SWMBO just finished the cloth tube for it that slides over the webbing cross belt and holds the USB battery cable in place.
    The USB battery can be carried in the pockets or in a small bum bag.
    PMSA003x.jpg
    The sensor communicates by blue tooth to the micro controller.
    If I walk away from the shed it just stops counting a reconnects as soon as I walk back into the shed.

  16. #135
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    This is something I have been thinking about for a while and finally cranked up the data and spreadsheet to do the maths.

    It relates to these new sensors that only measuring up to 10 microns whereas the current OHS wood dust exposure standards relates to dust up to 30 microns.

    The current recommend 1 mg/m^3 (1000 ppb) OHS limit is specified for dust smaller than 30 microns.
    When that standard was adopted industrial hygienists had a limited understanding of how wood dust behaves and what dust was more significant and what was less.

    Unless woodworkers expose themselves to a direct sawdust streams (e.g. lathe) the dust from 30 to about 15 microns will not make it up an operators nose so is by and large irrelevant.
    If lathe operators wear a full face shield this will reduce that exposure significantly
    The coarse dust also rapidly (minutes) falls out of suspension in the air and so does not usually contribute to significant time based exposures.

    In contrast dust smaller than ~12 microns hangs around worse than a bad smell andgets into ears, eyes, nose and mouth and causes the health problems.
    They is why all new dust sensors focus on dust around the 2.5 micron mark.

    Here is a graph using data I extracted from an article in Annals of Occupational Hygiene Vol 44.6 pp 455-466, 2000
    "A study on dust emissions, particle size distribution and formaldehyde concentrations during machining of MDF"
    Authors are Chung et al.
    As well as MDF there is interesting data for sanding and cutting pine and oak

    In this graph there are 4 data sets all relate to sanding pine using an 80 grit sandpaper.
    Finer grits increases the amount of finer dust so this works out to be about the worst possible scenario for the skewing of results by considering only the dust up to 10 microns.

    Sorry the scales are logarithmic (powers of 10) but I did that to more clearly show the data.
    The X axis shows the particle sizes in microns from 0.1 to 100 microns.
    The Y axis shows the % of particles of a given size

    The red squares are the % numbers of particles of different sizes <10 microns while the light blue diamonds are the % numbers of particles of different sizes >10 microns.
    The light blue go up to nearly 100 microns and the graph shows there are far less of the larger ones that the smaller ones (as one would expect for sanding)
    It turns out that some 80% of the particles is smaller than 10 microns while 20% are larger than 10 microns

    Now what about weight/mass or volume.
    The green triangles represent the %mass of dust <10 microns while the purple diamonds are the % mass for particles between 10 and 30 microns.
    Sanderdust-profiles.jpg

    Now the trend is reversed with the total %mass of the particles of <10 microns only being around 10% of the total mass and the dust between 10 and 30 microns representing 90% of the dust.

    What this means is if the new sensors only measure to 10 microns they won't see 90% of the 0 - 30 micron dust for this sanding process.

    The new sensor could thus be measuring 500 ppb but as that only represents 10% of the 0 - 30 micron dust, the real level of dust of <30 micron dust will be 5000 ppb.

    This is why comparing data obtained from these new sensors to the old OHS standard of 1000 ppb is a bit of a waste of time.

    If we assume the sensors are reading 90% too low then we should be targeting ~100 ppb as a general dust level to aim for.
    This of course only applies to "this sanding process".

    The article does provide dust distributions for some other processes and when I have some time and more importantly the inclination I will process those as well.

    Most recent dust studies in relation to health are focussing on the 2.5 and smaller micron dusts - notice that is where the peak of the sanding particle production is (red squares).

    Sorry this might come across as highly technical but hopefully it will be of use to some of you.
    Attached Images Attached Images

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