<html><body><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; color: #000000"><div>You came to the conclusion I did initially. I even searched to see if I could rent a 5K device. It is still on my radar.</div><div><br data-mce-bogus="1"></div><div>forced air is an interesting comment. The application notes for the Sharp do not talk about forcing air. I thought about running a small fan at 5v at reduced speed to imitate breathing via nostrils. That would create some movement. </div><div><br data-mce-bogus="1"></div><div>I'm redoing a bathroom and about a week ago an idea popped in my head suggesting a powered respirator. Masks suck. I sweat wearing one. </div><div><br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div><br></div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><blockquote style="border-left: 2px solid #1010FF; margin-left: 5px; padding-left: 5px; color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;" data-mce-style="border-left: 2px solid #1010FF; margin-left: 5px; padding-left: 5px; color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;"><b>From: </b>"Alex Carver" <agcarver+ale@acarver.net><br><b>To: </b>ale@ale.org<br><b>Sent: </b>Wednesday, June 8, 2016 3:03:11 PM<br><b>Subject: </b>Re: [ale] Sensor nuts<br></blockquote></div><div data-marker="__QUOTED_TEXT__"><blockquote style="border-left: 2px solid #1010FF; margin-left: 5px; padding-left: 5px; color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;" data-mce-style="border-left: 2px solid #1010FF; margin-left: 5px; padding-left: 5px; color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;">It's an interesting device but I think it's lacking for what you're<br>really attempting to do. The data sheet from Sharp does not make any<br>claims about the final particle size that it can potentially detect (not<br>measure, that's an important distinction). It mentions just "smoke" in<br>the datasheet which is probalby going to be around 1 micron diameter for<br>average smoke. However, there are a range of particulates in the air<br>that are smaller than 1 micron (the EPA tracks PM10 and PM2.5 which is<br>10 microns and smaller and 2.5 microns and smaller).<br><br>For a short list: Household dust has an expected range of 0.05 - 100<br>microns, atmospheric dust (important if windows are open) ranges 0.001 -<br>40, wood smoke is 0.2 - 3, rosin smoke (from solder) is 0.01 - 1,<br>tobacco smoke is 0.01 - 4, and anything combustion related including<br>cars is 0.01 - 2.5.<br><br>The problem with this detector is that it can't distinguish size, only<br>density. So 10 particles at 10 microns diameter is the same as 1<br>particle of 100 microns or 100 particles of 1 micron (roughly). It's a<br>reflectance measurement so it relies on the total cross section of all<br>particles in its field of view and makes an aggregate measurement.<br><br>This sensor will basically be able to tell you "this room is % dusty"<br>but it can't say "there's lots of floating hair combined with very fine<br>pollen or soot" or "your chimney flue is not open enough and causing<br>some smoke to back up into the house". It's also not a forced air<br>sensor so sampling is not going to be right since it will depend on dust<br>settling into the detector opening.<br><br>What you actually need is a forced air, laser based sensor that can<br>distinguish sizes. There are many around that could work within a<br>budget and give you some better numbers. Here is one I found with a<br>quick search of "laser particulate sensor":<br><br>http://www.dfrobot.com/index.php?route=product/product&product_id=1272&search=SEN0177&description=true<br><br><br><br>Or you can get more commercial versions that have more bins for the<br>particle sizes:<br><br>http://www.nano-sense.com/en/P4000/p4000-fine-particles-probe.html<br><br>http://www.sens2b-sensors.com/en/item/pm2-5-laser-particle-sensor-module-for-air-purifier-application<br><br>Just keep searching for other options but make sure it bins into various<br>sizes instead of lumping everything into a single measurement.<br><br></blockquote></div></div></body></html>