I need a simple pollen particle counter.

[mike]

I'm looking for cheap/simple way to measure relative airborne particle
counts for pollen-sized particles.
The objective is to get some feel for how well various furnace
filters work at filtering allergens.

Don't need any fancy features or accuracy, just general relative numbers.

REAL particle counters seem to work by shining a laser thru a cell
and measuring light reflected from the particles.
I did some experiments shining a laser pointer thru the air stream.
I could see the occasional flash, but it's going to take a lot
more optics and sensitive detectors than I'm willing to invest in to get
anything useful.

Cheapest particle counter I found was over $200, so that ain't
gonna happen.

Thought about charging the suspended particles and measuring
current in a collection plate. Simple concept, but I expect the
SNR is gonna be very low and the implementation not so simple.

My itchy eyes work well, but the time constant is LONG and the
uncontrollable experimental variables make it difficult to draw any
conclusions.

I'm looking for a clever idea to get some "feel" for how well
a particular filter configuration removes pollen from the air
without waiting for my eyes to get swollen shut.

Ideas?
Thanks, mike

 

[mike]

Would these things work?

http://sharp-world.com/products/device/lineup/data/pdf/datasheet/gp2y1010au_e.pdf
http://sensorapp.net/?p=479

Nice find.
I can't figure out if it would be useful for what I want.

I found a few papers on allergen concentrations, but don't understand.
They talk about densities in kg/l in one paragraph, then dilution
ratios in l/l. I haven't found enough consistent numbers to translate into
the mg/l of the sensor sensitivity spec.

Articles related to application of the sensor show it detecting visible
smoke from burning material. That's way more dense than what I
anticipate measuring.

I may have to buy one and just test it.
Thanks, mike

 

[Oppie]

This link below almost gets me excited:

http://circuitcellar.com/contests/designstellaris2010/winners/TI2822.html

Interesting - didn't know about the fluorescence aspect of pollen detection.
I had been thinking more along the lines of the old school smoke detectors
(circa 1960) that used a right angle light/sensor arrangement to detect
dispersed light from particles that entered a black box.
Oppie

 

[Oppie]

This link below almost gets me excited:

http://circuitcellar.com/contests/designstellaris2010/winners/TI2822.html

Circuit cellar article link is dead but did find this with full article
http://www.lpc1100designcenter.com/entry/?et=1246

 

[mike]

This link below almost gets me excited:

http://circuitcellar.com/contests/designstellaris2010/winners/TI2822.html

Me too.
It has some nice features.
It discriminates and counts only the biologic elements.
The excitation frequency is different from the detection frequency,
so optical filtering should be able to significantly increase SNR.

The closest thing I found to performance data was, "it's not very
sensitive."
Wish I knew what that meant.
To be useful, a device has to be able to discriminate pollen levels
around the threshold of hay fever symptoms.

I'm coming to the conclusion that it's easier to build a high voltage
supply than even a crude pollen detector. Might as well just build
an electronic air filter and be done with it.

 

[Oppie]

Me too.
It has some nice features.
It discriminates and counts only the biologic elements.
The excitation frequency is different from the detection frequency,
so optical filtering should be able to significantly increase SNR.

The closest thing I found to performance data was, "it's not very
sensitive."
Wish I knew what that meant.
To be useful, a device has to be able to discriminate pollen levels
around the threshold of hay fever symptoms.

I'm coming to the conclusion that it's easier to build a high voltage
supply than even a crude pollen detector. Might as well just build
an electronic air filter and be done with it.

Since the design was based on Fluorescence of the pollen grains, sensitivity
might be increased by either changing the excitation wavelength (the LED) or
the bandpass and center wavelength of the emission detector. Do a search for
"emission spectra of pollen" or the like and see what comes up.

 

[Winston]

I used to work in air pollution research. A guy built an instrument
to do this. It used a big old laser tube, I think you could do this
with a diode laser now. It focused a laser down to a small spot using
an 8mm movie camera lens (gives you some idea when I was involved in this).
There was a chamber that had a mild vacuum pulling on it, and a piece of
hypodermic tubing allowing in a jet of the air sample. The end of the
hypo tubing was near and pointing right at the focal spot of the laser.
There was a photmultiplier tube looking at this region from 90 degrees.
You could pipe the PMT signal to a speaker and hear the clicks, which was
good for aligning the optics. This thing would pick up VERY small
particles, pollen grains would be a lot easier. If you don't mind running
the pump, this setup could be run continuously for weeks or months
to get seasonal data.

That'd work much better with a linearly controlled
laser diode than with a PWM - controlled laser diode.

--Winston