Public Lab Research note


  • 7

Broadcast dust readings from a smartphone

by Schroyer |

The DustDuino project has been working for several months with environmental journalists around the globe thanks to a collaboration with the Earth Journalism Network. Based on the Shinyei dust sensor, which can detect airborne particulate matter in the PM10 and PM2.5 ranges, the DustDuino is an Arduino-based sensor node.

For information on how to build your own dust-sensing node, you can visit the DustDuino research note.

Development is ongoing, but in May, 10 journalists received prototype DustDuinos and training, as part of an EJN training seminar in Berkley and San Francisco, California. These DustDuinos were capable of connecting to WiFi networks to broadcast particulate readings to Xively, where the readings are stored and graphed for anyone to see.

These units were primarily meant to be kept in a home or office, where WiFi and power is readily available. Clara, an environmental journalist based in Indonesia, came up with a new method of broadcasting the readings from the dust sensor, wherever a cellular data network is available.

Step 1: create hotspot

Basically, if you have a smartphone or tablet that can generate a wireless hotspot, and your cell provider allows you use this feature on your wireless device, you can use this to connect to the internet and send dust readings from the DustDuino to Xively.

Alternatively, you can purchase a "MiFi" or similar mobile WiFi, and use that as your wireless hotspot.

Whichever the case, turn on the wireless device's hotspot feature or the mobile hotspot, and make note this wireless network's SSID and password.

Step 2: configure DustDuino

Make sure to configure the DustDuino's WiFly RN-XV WiFi module to connect to this wireless network, using the SSID and password. You will know the WiFly has been able to connect to the hotspot when the WiFly's red LED goes dark and remains off.

Step 3: find mobile power for DustDuino

You'll need to find a way to power the DustDuino, since you'll be away from mains power. You have several options to choose from.

80-01.jpg

If you've built your DustDuino out of the Arduino Uno and Arduino Wireless Shield, as outlined in the Public Lab research note, you can power the DustDuino using the Uno's 2.1mm DC power jack and a 9V battery. You'll need an adapter such as this to connect the 9v battery to the Arduino.

usb_portable_battery_power_charger_with_2500mah_capacity_639.jpg

Alternatively, you can power the DustDuino using the Uno's USB connection. Here, you can use a mobile cell phone power charger, such as this. These are essentially large lithium batteries that are regulated to output 5 volts, and supply that power over a USB connection.

gmgvpq1281075090393.jpg

If you are traveling in a car, yet another option is to supply power using a 5V USB adapter, plugged into your car's 12V outlet. Like the mobile cell charger, these were designed to charge your cell phone, but they'll power your Arduino Uno just fine.

Finally, failing those options, bring a laptop computer, and power the DustDuino via the laptop's USB ports. The advantage here is your laptop can connect to the wireless hotspot, so you can monitor the DustDuino's readings live from Xively.

Step 4: transmit!

If your wireless hotspot is active, and your WiFly module is configured correctly, and your DustDuino has adequate power, you should immediately be sending dust readings every 30 seconds to Xively.

With a mobile DustDuino, you can make and transmit particulate readings nearly anywhere. Clara obtained her readings while driving around. Where will you take your DustDuino?

ClaraDuino.png



particulate-sensing air-quality dustduino dust particulates particulate dylos

12 Comments

Hi there, I was just wondering if you ever debunked the claims by AQICN: http://aqicn.org/experiments/what-is-the-dylos-monitor-actually-measuring/ It would be great to hear your reasoning on that one. Thanks.


I just posted a comment to that article. thanks for pointing it out: @donblair-- the author doesn't seem to understand the terminology in use. The conclusions are based on a misunderstanding of what PM2.5 actually means I posted this comment:

PM2.5 is not the same as 2.5µ. it means particles with a mean aerodynamic diameter of 2.5µ. So a PM2.5 measurement is 50% above 2.5µ and 50% below. it includes 0.5µ particles. The same goes for PM10, it includes 2.5µ particles. https://en.wikipedia.org/wiki/Aerosol http://publiclab.org/wiki/particle-sensing


Are comments moderated there? I don't see your comment but it's a very important clarification to make. Thanks, Mathew!


yeah, l their comments are moderated. mine is still in the queue.


Love this project. Would you be interested in sharing the idea on an OpenHour? we have one on Air Quality scheduled for July 28th!


This article explains in some detail about the point Matthew just made: http://www.powermag.com/blog/pm2-5-more-than-just-dust/


Oh & this picture is just awesome too!: full-graphic.png


Wow Amy that is a SUPER visual explanation! Want to add it (with credit and maybe a "not open licensed" notice) to the particulates page? http://publiclab.org/wiki/particle-sensing


Sure - the source for that image is the link in the comment above it by the way.

I like super-visual. Apparently so does Stephen Hawking - who applied visual thinking to some really.complicated math & physics stuff!


@amysoyka The Powermag graphic portrays the PM fractions based on source sampling techniques used for power plant emission sampling. The source sampling techniques cool and condense the sample to a standard temperature. However, condensable and precursor fractions don't typically apply to ambient PM monitoring. Ambient PM monitoring typically measures whatever is naturally condensed at the current ambient temperature and precursors don't usually interfere.

@mathew The EPA definition of PM fractions can be found in 40 CFR Part 50, see http://www.ecfr.gov/cgi-bin/text-idx?tpl=/ecfrbrowse/Title40/40cfr50_main_02.tpl

"particulate matter shall be measured in the ambient air as PM10 (particles with an aerodynamic diameter LESS THAN OR EQUAL to a nominal 10 micrometers)"

and PM2.5 is a "LESS THAN OR EQUAL to a nominal 2.5 micrometers"

The 50% cut point refers to the EFFICIENCY at which particles are removed by the selective inlet at the given size. So for PM10, the inlet removes 50% of particles at 10 microns but above 10 microns the removal efficiency increases and below 10 microns removal efficiency declines. Thus the resultant fraction is not a normal distribution (e.g. 50% above and 50% below) but a skewed distribution (see graph below). Also, the rate at which removal efficiency changes is referred to as the cut point SHARPNESS.

The EPA definition is illustrated as:

pm.jpg

from Air Quality Criteria for Particulate Matter (Final Report, April 1996) see http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=2832 and go to downloads, volume 1 and scroll to around pdf page 127


Thank you so much for the clarification David! I'll work that into our summaries. its been hard to get a handle on exactly what is meant by that specification-- the graphic is really helpful too. I updated the wiki page: http://publiclab.org/wiki/particle-sensing


great visuals


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