air pollution particulate sensor package

The best method that I know of is to use a very dilute solution of polystyrene latex spheres. They're grown from solution, and are very uniform in size. You dilute them in very pure water (18.2 megohm-cm deionized, and filtered with an 0.014 um ultrafilter), with a very small amount of very clean surfactant (Triton from Fisher Scientific is the best), then atomize the solution with a medical aspirator (as used e.g. for administering Ventolin to pulmonary patients).

The water droplets form two populations: those drops containing one sphere, and those containing none. (You adjust the concentration so that doublets are very rare.) Because the water is so clean, the empties dry down very very small, leaving basically just the individual spheres floating round.

Cheers

Phil Hobbs

The Wiki is wrong there. Serpentine and chrysotile are two entirely different minerals, with different chemical composition, and biological reactions. Just why they are both classed as "asbestos", and treated as the same evil thing is just one of those mysteries which seems to stick around forever.

I worked for the Consumer Product Safety Commission at the time this regulation was being developed. At that time they were not sure just want caused lung disease. I remember my boss was attending meetings with EPA working on this. They seemed to feel the problem was fibers rather than the material itself, but they didn't know just what constituted a fiber. He said one prominent researcher defined a fiber as anything 3 times as long as it is wide. Another researcher responded that his car was a fiber under that definition. lol

People in this group love to criticize anyone at any time. We know a lot more now and have the huge advantage of not being under the gun to save lives which is exactly what they were mostly concerned with at that time. They couldn't delay while they waited for more studies, so they did the best they could with what they had.

If anyone feels the laws need to be reworked, then get involved and help shape some new legislation.

I find especially ridiculous the idea that today's brake pads don't stop the vehicles well enough. lol. I remember the junk being made in the US in the early 70's. Today's cars are the safest we have ever driven.

Metal brake pads have to warm up to work properly, whereas asbestos ones didn't. Of course, anyone who ever uses "lol" for anything might not understand actual data.

Cheers

Phil Hobbs

Yeah, beats hauling a ton of batteries up and down hills.

rickman:

Defective car keys, exploding airbags, engine controllers sensitive to RF. batteries on fire. Poisonous cooling substances. The list is endless.

You are wrong.

That is one of your dafter posts Jan...

snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:

...

Check "Dylos dc1100 pro." It is cheap and reliable.

Mass.

--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@netfront.net ---

Thank you for the suggestion.

I believe that for my application, the price point of the Dylos is too high for widespread deployment. Also, as mentioned in my other post, it is desirable that the unit be able to be read (via bluetooth?) by mobile devices, such as cellphones.

nasty

Be glad if you don't live in an area with naturally occurring asbestos. I live near lots of them.

?-)

help

Actually the current legislation is nearly correct. It is set up so that regulation does the adapting, by leveraging the best repeatable science available.

stop

driven.

Metal in brake pads came in well before asbestos went out. Its superiority in thermal fading resistance to non-metal brake pads made it a market winner.

Brake fade isn't caused primarily by hot pads, it's caused by boiling brake fluid. And earlier metal pads also contained asbestos.

Cheers

Phil

I encourage you to talk with the docs on the phone at the NIH SBIR National Heart Lung Institute, as I remember. You said you were not skilled at electronic design - these docs know even less. The NCI also a possibility. It's going to take the resources to develop what you want - The docs are quite encouraging, often.

And, whether or not you know it, you are a legitimate developer of low cost particulate detection systems. If you talk with the docs on the phone, you would be primarily asking them questions, such as, "Is this a legitimate topic to apply for?" and "Do I need to partner with a researcher in this field?" (probably both yes.)

Natural asbestos isn't a big problem. It's the results of the machining of the stuff that makes the nasties. Rocks don't often get into the lungs.

I added 2 more photos of the inside of the light box to the web pile:

Thanks. That is very interesting. In Nikken-AQM-09.jpg, the BA10324A looks like a slow op amp, similar to the LM358

I'm surprised the particles really move that slowly through the focal point that the BA10324A can follow them.

I see the symbol for Q2, but I can't find Q1. Did they miscount, or is it somewhere on the other side of the board?

D1 and D2 look like dual diodes. Is this some kind of log converter? Your photos are excellent, but it's kind of hard to trace the circuit looking at black traces on a black soldermask. I'll wait until mine arrives so I can trace the circuit.

Maybe an optical illusion, but the board seems very thick looking at the two screw holes.

I'm glad you were able to get it apart without destroying it. That means I can try monitoring the signals.

Mine should arrive next week and I'll compare the readings with the Dylos.

It would be nice if the Nikken can get down to 0.5 micron. It is battery powered and would be a lot more convenient than lugging the Dylos around with the power cord. It's a bit awkward trying to find an AC outlet, especially if it's far from where I want to monitor.

Very interesting. Thanks, Jeff

LM358 is a dual op amp. The BA10324A is a quad op amp. Probably more similar to an LM324.

Note the two lenses on the IR emitter and detector. It looks like they focus the light to a point in the middle of the circular area where the tube delivers air flow. It's probably difficult to detect with a diffused light source, but one that's concentrated almost to a point should be fairly simple (famous last assumptions).

Probably other side. I couldn't get to the back side of the PCB as the leads for the IR emitter and detector were both soldered from the bottom of the board. There may be a mess of components on the circuit side but I could tell without unsoldering.

No clue and I've already reassembled the device (this time plugging in the connector I forgot last time).

I'm still trying to figure out what the insulated plate in the middle of the air duct is doing. I forgot to see if there's any high voltage when I had it apart.

I didn't measure it but it looked like ordinary 0.032 inch G10/FR4.

Yep. It was something to do while Windoze 8.1 was slowly installing.

Cheap on eBay for about $30.

I could probably blow some dust into it and see. However, my guess(tm) that is works best with large particles that scatter the light better.

Yep. 3.7v Li-Ion cell phone battery which is easily replaceable.

Picky. I said similar. The LM324 is a quad 358. I was talking about the basic input structure and bandwidth. Differential PNP so the common mode extends to zero volts, and low bandwidth.

That's the issue. How fine is the focal point, and how fast do the particles move through?

Maybe wise. The IR emitter may be sensitive to ESD. But I'd expect some vias to connect to the other side.

I'll trace the circuit and see what it does.

Yes, I thought that was strange. Wouldn't high voltage need a corona generator upstream? Maybe it's a light baffle.

Tee hee. I'm running XP in a vm. Takes about 45 seconds to recover from a crash that crosslinks clusters. Happened again today. No problem.

There were a half dozen or so when I looked. Some went as high as $400. They are all gone now. Mine was $17.99 plus $16.34 shipping.

The large particles don't do as much damage as the small ones, which lodge in your lungs. According to the Dylos measurements, the small ones are about ten times more numerous than the large ones. But I found a different environment yesterday where the ratio was closer to 16%. That should be telling me something, but I don't know what yet.

I'm really interested to see some waveforms. As far as I can tell, the Dylos and Nikken may operate the same way, so I'm expecting similar results. I'm hoping to be able to tweak the Nikken to get down to 0.3 micron or lower. Maybe add a comparator to exclude the large ones, and a pot for variable thresholds.

Very interesting. Thanks, Jeff

Well, the spot diameter could be measured. The emitter doesn't look like anything special. Just an ordinary LED operating in near IR region. You can see near IR with a digital camera (try it on your TV remote control). A little cancerous cigarette smog, and the light beam should be visible.

I'm sure I could have removed it without much difficulty. I just didn't think it was worth the risk. I'm more worried about trashing the calibration than breaking anything.

Please note that it was a guess(tm) as to the purpose of the insulated plate. I still don't understand its function as the plate is NOT in the air flow going to the optical dust sensor. I'm fairly sure it's not a high voltage system because of the nylon insulators and the lack of any high voltage components on the PCB. More Googling, I guess.

How the IR dust sensor works: Sharp:

Shinyei: Taking it apart (with schematic): Outdoor air monitoring in Beijing: More of the same:

That's what happens when people read this newsgroup. There are still 3 for sale/auction:

According to my random reading, one can distinguish between various types of dust sources by the waveform.

That's down to the size of mold and possibly bacteria.

You can differentiate particle size by pulse width. The Shinyei detector claims 1 micron minimum on the data sheet. My guess(tm) is that something in either the amplifiers that follow or the air speed limit the upper frequency response. The faster the particle goes by, the narrower the pulse. You might be able to slow down the air flow in order to "stretch" the pulse width.

Another possible way might be to artificially increase the particle size by making small particles clump together as in an electrostatic precipitator. Equal air flow through two different ducts. One duct would give the dust particles a positive charge, the other negative. When recombined, they would clump together forming roughly spherical ummm... clumps, which should produce a much larger pulse width.

Good luck.