Date:	Fri, 6 Jan 1995 14:08:53 -1000
From:	erikp@login.dknet.dk (Erik Petersen)
Message-Id: <4153.erikp@login.dknet.dk>
Organization: Harvard University Office of Information Technology
Subject: Re: D-I-Y hand-held anemometer

I haven't yet come to build this anemometer, I'll decripe here, but then
again I can't see, why it should not be easy to make or why it should not
work:

My idea is to utilise the fact that if you have a constant current through
an semiconductor diode, the diode voltage is dependent of temperature.  A
rule of thumb states that the voltage vil drop 2.3 millivolt per Centigrade.

If your are not into electronics, stop reading here!    :-)

Now if you have two diodes, one shielded from the wind,
and the other exposed to the wind in a sort of bridge circuit, then changes
in ambient temperature will balance out, and the bridge voltage will
increase with the wind.

Notes:
   1) This anemometer will be as omnidirectional as the rotating cup,
      but will take up very little space.  You could actually let the
      lift it up.
   2) Put two or more diodes in series, and boost your output.  10 diodes
      will give -23 mV per Centigrade!
   3) Add an DC-amplifier to increase sensitivity.
   4) Make sure, that the diodes are really HOT, so the cooling effect of
      the wind can be observed.
   5) Keep the supply voltage at 9 volts or higher - and *dont* cheat with
      the constant current source!

You could also
   ... let the output voltage change the frequency of a xtal oscillator and
   then determine windspeed with a shortwave receiver.

I better go build one to prove that it works instead of ravelling on.

A final note in Danish to Rolf:

; Er du den samme Rolf V. Oestergaard, som jeg har observerer foerste gang
; "Pgm" Texas programmerbare lommeregnere, og senere i de gode gamle
; ZX-Spectrum og Sinclair QL-dage?   Det maa det vaere.
; Det glaeder mig, at du har set lyset og ogsaa flyver drage og derved
; faar menneskene til at se fremad og opad!
;
; En dag du har god tid, maa du skrive og fortaelle, hvad du nu beskaef-
; tiger dig med.


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