Here's an idea a bit "outside the box":
What if (my favorite phrase) you mounted a laser LED in front of a horizontal and vertical adjustable slits (to control the beam width) in a sealed environment then mounted a photo-detector at some distance from the slits with a high speed counter. This would present a fixed volume (aperture size X length) and if an airflow was controlled across this "envelope", one might be able to determine a reasonably accurate concentration.
Another thought, isn't there an instrument to verify clean room contamination?
Ed Popielarski
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Thursday, August 29, 2013 7:07 AM
To: [log in to unmask]
Subject: Re: [TN] Blowing Smoke
To answer previous question:
The idea is a cheap sensor. 3rd world homes are notoriously smoky due to the cooking fire and due to kerosene lamps. Most of the smoke is carbon. There are lots of ideas for improving these homes (like LED lights with solar rechargers) so we can "improve their lot" by making it more healthy for kids to study inside (or maybe so they can buy stuff on the internet?). Anyway, the aid groups want a way to see what the bang for buck is in improving the indoor environment, so they need a sensor. These sensors work by shining an LED or laser through an air stream, and measuring the amount of light which is reflected off-axis by the particulates in the air.
How does the bicycle pump (actually I'm imagining a disposable plastic syringe) pick up a defined amount of cigarette smoke? Maybe arrange a fixture which leaves the cigarette burning and allows the smoke to just rise into the open end of the syringe for a set amount of time, then put the plunger in. Might work-cheap to try!
As to the other suggestions, such as the nichrome wire, I keep coming back to needing some kind of heated basket so I can make sure I burn 100% of whatever I put in there. A circulating fan and Brownian motion should make the environment pretty uniform, although with the tests I've been doing, I get a spike with an exponential decay as the particles settle. Still, the interior of the 5 gallon bucket appears pretty uniform, even though the peak duration is only about 40 secs.
Wayne
From: Inge Hernefjord [mailto:[log in to unmask]]
Sent: Thursday, August 29, 2013 4:45 AM
To: TechNet E-Mail Forum; Wayne Thayer
Subject: Re: [TN] Blowing Smoke
Don't laugh now, I am serious. A kind of cycle pump, but with a very small diameter nozzle. Pull the handle and suck a second sniff of cigarett smoke, continue pulling handle until pump is filled with air/smoke mixture. Now press handle slowly and you get a constant stream of mixture. Simple and cheap. Guess the nozzle should be fractions of a millimeter.
Inge
On 28 August 2013 08:07, Wayne Thayer <[log in to unmask]<mailto:[log in to unmask]>> wrote:
OK, here's another problem I've been playing with (although it has little to do with IPC mission, it might be related).
I am trying to build a system for measuring airborne particulates for humanitarian organizations looking for inexpensive ways to measure/monitor indoor air quality. There are cheap sensors available which might do the job, but they would need periodic re-calibration.
So I need a controlled, extremely small amount of smoke. At first, I thought this would be trivial: Find a cheap part at DigiKey and put too many watts through it. Way too much smoke and too little control. Then I tried burning thin wires. Too irregular because sometimes they incinerate completely and other times they find a tiny defect and just burn that until the wire stops conducting. Then I tried just heating the wire enough to burn off the insulation. Still too irregular! I did just a few experiments and got 30% variation.
Now I'm starting to think maybe a tiny piece of paper on an automotive cigarette lighter. That's a lot of power to get that glowing, and it is not convenient to attach to. Any other ideas?
Wayne
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