I need a simple pollen particle counter.

The old way was the "roto-rod". You put a piece of double-stick tape on the end of a rod and have a motor spin the rod. The particles get stuck to the tape, then you count them under a microscope.

Jon

Would these things work?

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

This link below almost gets me excited:

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

Circuit cellar article link is dead but did find this with full article

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.

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.

Jon

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.

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

--Winston