basic stamp pollution detector - help needed

Humanoido

Help! I need a simple way to make a basic stamp pollution detector. A web search did not find any simple hobby sensors. Any ideas for a method?

Here's the setup. Each day in the big city, the air contains varying amounts of pollution. Wind currents bring in smoke, dust, manufacturing chemical, and smog.

Currently, pollution level is rated from 0 to 10 by eyeballing a tall skyscraper located in the distance. If it's not visible (0), the pollution is bad. If it's clearly visible with windows (10), there is no or negligible pollutants.

Several times, I either left the window open at night, or unknowingly went outside, forgetting about the level of pollution, and developed serious allergy creating weeks of down time, misery, and trips to the hospital.

A simple detector could sample the air from a small distance, i.e. 6-inches from point A to point B, and report a number that determines the amount of obscurity. I'm not looking to identify smoke, dust, fog, smog, chemical or the type of pollutant, but rather to identify the amount of obscurity in the air.

There's LEDs and photodetectors, cheap & simple, but how to get the level of sensitivity required? The light path could be folded with mirrors to increase the sampling distance in a small space.

Any ideas?

humanoido

Mike Green

How about using a carbon monoxide or hydrocarbon detector as a proxy for particulate matter? SparkFun carries them.

stamptrol

The fog detector at many airports works with a controlled light source and a detector. Basically detects the relative obscurity between the light source and the detector.

You may be able to control the current in an Infrared LED so that the IR detector can barley detect the beam under clear conditions. Then, as the obscurity builds up, the detector output will drop (probably not linearly, but you may be able to build a LOOKUP table).

Cheers,

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Tom Sisk

http://www.siskconsult.com
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Humanoido

Thanks sincerely for the responses. This rings an idea about measuring the back scattering of light created by varying amounts of pollution. Interesting that Penguin robot is fully equipped to do this, with an infrared transmitter and detector. If the PBASIC code generates and responds only to a pulsed signature, stray and solar flood IR can be minimized for the detector's daytime use. Any comments on this approach and recommendations?

humanoido

allanlane5

This might work.

Limiting factors include that it's difficult to 'tweak' the output power of the IR-LED. Also, the "Detector" is optimized to eliminate 'stray' signals.

However, people HAVE shown that with the BS2, if you output different freqencies than the 38,700 "most sensitive" one, because of the way the BS2 outputs these, you CAN issue signals which are "easier" or "harder" for the Detector to lock onto. So with some experimentation you might get that to work.

Humanoido

Is this the "zone technique" that you're talking about,
to determine general distance to an object? I didn't see
any specs about the accuracy, as it appears to be relational
to the frequency increment. How small an increment is
workable? I'm trying to get an idea of how small of a zone
is possible, and hence the accuracy of the reported distance.

humanoido