Sorry, 1st mail didn't have a "Who" entry....


How would you like to count practically every raindrop?

A piezoelectric disc is connected to a MCU's ADC (PIC of course) through an
interface circuit (peak voltage limiting, variable gain amplifier and a
digitally programmable filter).

What it does is "listen" for raindrops. How will it know it's rain or
birdseed? Heavy rain or a light drizzle? And more importantly how much rain
is falling?

By knowing the "signature" of falling raindrops and the amount. Use a
piezoelectric disc of known area (say 1 inch dia) and calibrate a table of
signatures for a known amount of rainfall. The PIC will set the interface
amplifier to maximum gain and wait for any "hits" to the piezoelectric
element. Once *any* hit is detected (birdseed, sand or rain), the PIC sets
the amplifier gain so that the peak signal to the ADC is at say 3/4 of full
scale. The PIC then sets up the programmable filter for whatever it's
supposed to detect, in this case "RAIN".

So by varying the gain and filters the PIC can be programmed to detect and
count a specified object (sequencial hits) or to determine the approximate
amount of a specified object (averaging hits).

Slanting the piezoelectric disc at an angle is necessary to prevent the
counted object or liquid from accumulating on the sensor. Thin aluminium,
glass, ceramic, steel, teflon, etc can be attached to the piezoelectric
element for wear resistance and/or electrical insulation.

Benefits are, it will have no mechanical moving parts, no corrosion,
adaptable to function as a rain detector, liquid flow detector or count
small falling objects like screws, nuts, ball bearings, etc.

A patent search i did in Dec '98 has a similiar but simple circuit to count
seeds as they were discharged from a farm machine (seed sowing). I offered
my improved idea for a local development grant and nothing came of it. So
if this improved idea is "new", so to speak, and doesn't infringe on any
existing rights. It's free to anybody that wants to use or develope it. I
sure hope the piclist is used for a prior art patent search coz i'm not
going to patent this and it'll be available to any and everybody that
want's it.


Cheers
Terry



At 02:48 PM 2/17/00 +1100, you wrote:
>I have a friend interested in making his own logging weather station. I
>was wondering if anyone had any ideas on how to measure rainfall for such
>a project.
>
>___________________________________________
>Wesley Moore
>RMIT - BEng/BApp.Sc. 2nd Year
>
>wmoore@cs.rmit.edu.au
>http://wmoore.tsx.org/
>