Homemade disdrometer, programming help wanted

[bengomez]

Somebody should look into the technology used for drum pads. These are rubber like pads that produce a signal proportional to how hard you strike them with a drum stick, and are used as inputs to trigger drum machines. If we could make one that is much more sensitive...

Along this line, what about a sensor based on the condenser microphone principle. Two charged plates are placed close to each other. When one of the plates vibrates, the capacitance between them changes, which produces a changing voltage. I had thought about stretching a sheet of aluminized Mylar, as a diaphragm, a short distance above an aluminum plate. However, this would have a few problems: the diaphragm would ring with its natural frequency when struck, it would respond differently when struck near the edge than in the center, if it was hit hard enough the diaphragm would touch the aluminum backplate and short out the whole thing.

How about putting some closed cell foam dielectric in the middle? Some of that sheet packing material you sometimes get, about 1/32 to 1/16 inch thick. Using contact cement, glue it on to an aluminum plate, and glue some space blanket material on top, aluminized side down. The foam is resilient enough to deform a little when a drop falls on the diaphragm, and thus produce a signal, but it would restrict the deformation to a small region, giving the same response at different locations on the sensor. The internal friction in the foam would provide damping and keep the diaphragm from ringing, and it would prevent the diaphragm form shorting out when struck too hard.

Steve

Yeah using contact cement, glue it on to an aluminum plate, and glue some space blanket material on top, aluminized side down....

_________________
aluminum plate

[Weather Display]

old thread digging up here, sorry
I have found a component that gives the volume as a raw value so that it can be stored and plotted
so that I could now add support for a home made disdrometer into WD if anyone wanted to make one
(i.e to get a plot on say the main graph, or real time graph , or advanced graphs, of the volume (which goes up the heavier the rain) from the disdrometer)

[Weather Display]

support for a home made rain disdrometer sensor has now been added to WD
to the latest zip update
see under setup, advanced/misc, rain...
works in testing here , using a microphone and talking into it

the data plots on the wind direction graph and there is a custom tag available too, %flatplatesensor%

[sloweather]

Of course, after Brian added support for this to WD, it promptly stopped raining here, in the heart of our "rainy" season. This is shaping up to be the driest winter here on record. Fortunately, La nina is breaking down and the eastern Pacific high has shifted enough to open the storm door for us. Last night it rained and I finally got a chance to test the new addition.

The disdrometer trace is the dark line on the wind direction graph. The trace just after 1500 is me hooking everything up and testing it. The rain started about 2100 and it rained most of the night.



Setup is under Setup-Advanced/Misc Settings on the Rain/Wind/Lightning tab. I had to fiddle with the Max Average Count graph Scale to get the trace scaled appropriately, and wound up using a setting of 4000. Hint: If you set this to less than the base value when it's quiet, the trace will scale all the way off the graph and you won't see it at all.

Here's the overnight rain rate graph from VWS for comparison:

[TokKiwi]

That looks so cool!  I'm glad it all worked - now a few more will get interested.  Well done Brian - looks like it is working just as planned!

[eongibier]

Hello Brian,
(Sorry for my English, it is about a translator)
Can you specify me if my Vaisala WXT520, will be compatible and if possible to adapt %flatplatesensor%.
As the detection of hail is possible I think that is fart feasible being, without an acoustic system?

Good day.
Serge

[Weather Display]

no, its not related to the hail detection from a wxt510
the wxt510 has these custom tags already
%vaisalahailaccum%
%vaisalahailpeak
%vaisalahailinte%  (intensity)
%vaisalahaildura% (duration)
and
%vaisalaanalog%  (anlog input value)

[eongibier]

Ok Brian,
Merci
Serge