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'Windspeed circuit? [OT]'
2000\01\14@144641 by jamesnewton

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Now the question is: Where does one get (buy or make) the wind vane?

How about wind mills? Any sources for making or buying the business end of a
wind power system?
I need a low cost to make, $0 to operate water pump for my passive solar
heat storage system design.

BTY: See, you can edit the Subject line to add [OT] ;)

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{Original Message removed}

2000\01\14@153230 by James Paul

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Guys,

I used a propeller from a model plane one time to turn a motor
in wind.  I wasn't measuring wind speed with it as it were, but
I guess I could have.  Anyway, a two or three balde prop ought
to do the trick.  For a pulse generator, you could also use a
part of an old mouse probably.  Just count the pulses in a
given period, and transform that number to wind speed.


                                      Regards,

                                        Jim


On Fri, 14 January 2000, James Newton wrote:

{Quote hidden}

> {Original Message removed}

2000\01\14@154228 by Jim Hartmann

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Did anyone mention the hot wire anemometer?  I've also seen a "hot
transistor" anemometer as a Design Idea in Electronic Design, here->
devel.penton.com/ed/Pages/magpages/may2598/ifd/0525ifd.htm
Scroll down past the first article.

-Jim

2000\01\14@161229 by Ken Webster

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>Did anyone mention the hot wire anemometer?  I've also seen a "hot
>transistor" anemometer as a Design Idea in Electronic Design, here->
>devel.penton.com/ed/Pages/magpages/may2598/ifd/0525ifd.htm
>Scroll down past the first article.
>
>-Jim

Aaahh! Beauty!

A PIC could do that much better!  With a little computation the nonlinearity
could be completely accounted for.  Plus you could use simple thermistors
instead with the PIC reading them and controlling the current through the
hot one.  Since thermistors come in really tiny packages with low thermal
mass (much smaller than the TO-92 that the LM334 comes in) you could get
much faster response time.

This sounds fun!  Now if I can just scrape together the time to play with
this...

Cheers,

Ken

2000\01\14@161650 by Peter L. Berghold

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On Fri, Jan 14, 2000 at 02:37:29PM -0600, Jim Hartmann wrote:
> http://devel.penton.com/ed/Pages/magpages/may2598/ifd/0525ifd.htm

Oohh... I like it.... Now there's something to play with! ;-)

It would seem to me that you could also create a hydrometer with the same
circuit using wet/dry "bulb" methodology...

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2000\01\14@162815 by Jim Hartmann

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The fellow who wrote that one writes MANY, all are brilliant or at least
very interesting.  Search the site for "Woodward".
-Jim




"Peter L. Berghold" <.....peterKILLspamspam.....BERGHOLD.NET>KILLspamspam.....MITVMA.MIT.EDU> on 01/14/2000
03:14:18 PM

Please respond to pic microcontroller discussion list
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Subject:  Re: Windspeed circuit? [OT]


On Fri, Jan 14, 2000 at 02:37:29PM -0600, Jim Hartmann wrote:
> http://devel.penton.com/ed/Pages/magpages/may2598/ifd/0525ifd.htm

Oohh... I like it.... Now there's something to play with! ;-)

It would seem to me that you could also create a hydrometer with the same
circuit using wet/dry "bulb" methodology...

--
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"Linux renders ships                     http://www.berghold.net
NT renders ships useless...."

2000\01\14@171547 by Barry King

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> Now the question is: Where does one get (buy or make) the wind vane?

This is what I do for a living.

<commercial>
Check out http:\\http://www.nrgsystems.com
Our anemometers are the best value around.  (Not quite the
cheapest)
</commercial>

Or look for "weather stations" on the web, several cheap sensors are
available.  Most of them work.  At least moderately well.  At least for
a while.  :)

In the industry, the term wind "Vane" is a wind direction vane,
commonly known as a  "weather vane", it swings around into the
wind to measure wind direction.  (Ours have a special potentiometer
so the PIC can read back wind direction using A/D).

What you want for a rotating anemometer is either a cup-wheel
(vertical axis, usually 3 cups), or a propeller of some kind.

The aerodynamics of propellers are very complex so they tend to be
non-linear. (there is a lift component as well as a drag component
generating the spinning torque).

The aerodynamics of cup wheels are drag only, so they tend to be
fairly linear, once the wind is giving enough torque to swamp the
bearing drag.  If you roll your own, you'll have to calibrate, which is
non-trivial.

For cheap and PIC-compatible, (besides my own products), check
out the Dallas "1-wire" weather station.  It has a cup anemometer
which goes onto that bus.  It was a demo / promotion last year, their
web site might still have the info.

>
> How about wind mills? Any sources for making or buying the business end of a
> wind power system?
> I need a low cost to make, $0 to operate water pump for my passive solar
> heat storage system design.

For homebrew stuff, look at Home Power magazine.  They might
have a web site, can't remember.  My opinion is that homebrewing
this kind of stuff is rarely "worth it" (that is if you count your time),
but it might be fun anyhow.   Any project that requires a PIC AND
an arc welder is always interesting.  :)

Regards,

------------
Barry King, Engineering Manager
NRG Systems "Measuring the Wind's Energy"
http://www.nrgsystems.com
Phone: 802-482-2255
FAX:   802-482-2272

2000\01\14@192743 by Quentin

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James Newton wrote:
>
> Now the question is: Where does one get (buy or make) the wind vane?
>
A hobby method is to take two Ping Pong balls and cut them in half.
Mount that on a spindle and Voila!

Quentin

2000\01\14@201722 by William Chops Westfield

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Circuit cellar awarded/published a weather center a couple years ago,
which included (IIRC) construction info on the mechanics (bunch of PVC
pipe?) as well as PIC circuitry (are we on-topic again?) to read the
sensors AND directly drive video...

I suspect some of it is probably still on their web site.

BillW

2000\01\15@133405 by Gaston Gagnon

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James Newton a icrit :
>
> Now the question is: Where does one get (buy or make) the wind vane?
<...>

Dallas offers a nice kit (easy to assemble, a few screws) which
includes: wind direction, wind speed and temperature measurements for
$79.
They also host a weather mailing list which is quite active.
       http://www.ibutton.com/weather/index.html

<...>
Gaston

2000\01\15@143930 by Sean Breheny

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I haven't looked at the article, but why should non-linearity be an issue?
Why not just make a temp controller which uses a transistor in a constant
current configuration to heat a thermistor, and the whole thing is exposed
to the air? You use the controller to maintain a constant temp,and then
just measure how much voltage is being delivered to the transistor and that
is linearly proportional to the heat delivered, again linearly proportional
to the heat being lost. Then, the only non-linearity would be in the
interaction of the air with the sensor.

Sean

At 02:14 PM 1/14/00 -0700, you wrote:
{Quote hidden}

| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
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2000\01\15@183044 by Wagner Lipnharski

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You should use two temp sensors, one enclosed, another exposed, if not,
your will ending up measuring air temperature instead velocity.

The linearity issue was created by my generation, at a time when
microcontrollers and data processing was not possible, so transistors
would indicate values in a simple milliamper meter (dumb indicators).
At this age with fast microcontrollers, e2proms (to hold calibration
tables) and interpolation routines, it is a shame that people still
wasting gray brain power to solve the problem at the front-end and using
all the silicon potential as the old dumb meter.

Sean suggestion is nice, but how it will discriminate between a wind of
3mph (10¡F) and 40mph (80¡F)?  It needs an enclosed second sensor,
creating a delayed Delta-T reference.  Even so, there are many induced
errors in this kind of air speed measurement. I believe that today's
cheap low pressure sensors can be more effective (temp compensation and
else).

Wagner Lipnharski - UST Research Inc.
Orlando, Florida  - http://www.ustr.net
---------------------------------------

Sean Breheny wrote:
{Quote hidden}

2000\01\15@224601 by Sean Breheny

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Hi Wagner,

You are absolutely right, you would have to know the temperature to
determine the wind speed. However, I don't see why it would have to be
enclosed. As long as the second thermistor is not self-heating, then it
shouldn't matter if the wind is blowing around it. Although, the need for a
second sensor (and therefore,the need to determine the difference in temp
curves between them) makes my idea less attractive :-(

Sean

At 06:30 PM 1/15/00 -0500, you wrote:
{Quote hidden}

| Sean Breheny                  
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student  
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2000\01\16@000939 by Alan Aldaba

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Hi everyone,

       A solid state wind speed indicator (anemometer) was featured in
Electronics Now - November 1997 issue. According to the article , it is
based on a "hot-wire" technology..,the heart of the sensor is a self
-heating npn transistor. IMO, the circuit could be easily converted to
use a PIC...

All the best,

Alan

Jim Hartmann wrote:
>
> Did anyone mention the hot wire anemometer?  I've also seen a "hot
> transistor" anemometer as a Design Idea in Electronic Design, here->
> devel.penton.com/ed/Pages/magpages/may2598/ifd/0525ifd.htm
> Scroll down past the first article.
>
> -Jim

2000\01\16@001524 by Wagner Lipnharski

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Sean is right, even that I never build such thermal wind speed sensor.

What counts here is the heat loss caused by the wind. If one sensor (SH)
is self-heating and another is not (SC), and considering that SH try to
keep a stable temperature (by changing current), then when wind = 0 the
reading between both sensors would be equivalent to the delta between
SH_Temperature and SC_Temperature (ambient).  Now suppose SC_Temperature
(ambient) changes, that delta will change accordingly.  

When wind > 0 then this delta will also change.  So, to make sure the
delta would be converted to a correct wind_speed_value, then
SH_Temperature should be a known constant, and SC_Temperature (ambient)
should also be read to be a parameter at the "delta" calculation.
Initially I was thinking to enclose SC to react slowly to wind
temperature variations, so changes in "delta" would be registered more
suitable with better resolution, but it seems that it is not totally
necessary, since if the wind carries a different temperature than the
ambient, it will interfere in both sensors at the same time, so more
accurate.  I guess I made some mixup with the rain detector using both
thermal sensors, when one is protected and another exposed to rain.

The only problem in keep SH_Temperature constant is that this temp
should be higher than the highest possible ambient temperature for that
particular location, so, lots of wasted energy to heat the sensor in
deep winter.  Up North you guys can have +90¡F in summer and -30¡F in
the Winter, so to work ok, SH_Temp should be at +95¡F all the time,
right?

I guess that it could also be possible trying to keep SH_Temp few
degrees above SC_Temp and using the microcontroller to do its job of
some calculation and conversions. Lots of energy would be saved (at
least in portable or battery operated units) when heating SH to -20¡F
(instead +95¡F) when SC is at -30¡F.

By other side, if a constant current is applied to a heater around SH,
and measure SH and SC resistance, SH will always be warmer than SC, so
this "delta resistance" along with SC resistance could be used to
calculate wind speed, with a fixed and low power consume. Somehow as
SCÖ(SH-SC) and apply linearization + tables calculations.  

I believe that the constant current solution has a faster accuracy
recover to ambient temperature fast changes, than the constant
temperature solution.  In the constant temperature, a 10¡F change in the
ambient temperature caused by a chilling wind will require some time to
stabilize SH_Temp, causing wrong readings or long delays. In the
constant current it doesn't matter, the calculation result will depend
only on the wind factor.

---------
Question:
Anyone can recognize a windy day by the wind whistle in fences, trees,
etc, so, why not use this solution? A frequency meter based on a special
wind whistle frequency? Probably not accurate for wind speeds lower than
10mph, but could be practical for certain applications.

Wagner.

Sean Breheny wrote:
{Quote hidden}

2000\01\16@044944 by Michael P Olson

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>The only problem in keep SH_Temperature constant is that this temp
>should be higher than the highest possible ambient temperature for that
>particular location, so, lots of wasted energy to heat the sensor in
>deep winter.  Up North you guys can have +900F in summer and -300F in
>the Winter, so to work ok, SH_Temp should be at +950F all the time,
>right?

>I guess that it could also be possible trying to keep SH_Temp few
>degrees above SC_Temp and using the microcontroller to do its job of
>some calculation and conversions. Lots of energy would be saved (at
>least in portable or battery operated units) when heating SH to -200F
>(instead +950F) when SC is at -300F.

What about air density? It seems like I've seen something similar to this
(constant current heater) used in the intake manifolds of automobiles to
determine fuel injection settings. Would the heat transfer be the same at
1,000 ft (300m) as it is at 10,000 ft (3,000m)? This may limit the unit's

usefulness to 'local' areas (i.e. altitudes where it's been calibrated).
Anyone for 3-d lookup tables?

You'd definitely need two sensors, both exposed I think. One could be
'up wind' of the hot wire, one 'down wind'. This would make the finished
unit a bit more compact.

              >>>>>>>> SC >>>> Hot Wire >>>> SH >>>>>>>>>>>

>Question:
>Anyone can recognize a windy day by the wind whistle in fences, trees,
>etc, so, why not use this solution? A frequency meter based on a special
>wind whistle frequency? Probably not accurate for wind speeds lower than
>10mph, but could be practical for certain applications.

As a (very) amateur recorder and tin whistle player, I don't think a
'regular'
whistle like you find in the mouthpiece of a referee's whistle or musical
instruments would work. They tend to put out a constant frequency until
the air pressure reaches a certain level, then they 'pop' up to the next
octave.

I have heard of a thing called an Aeolian Harp. It's a sound box fitted
with a
series of strings (all tuned to the same frequency!) that fits into a
window
frame. The breeze blowing in over the strings is supposed to make music
by vibrating the strings. Changes in velocity (and turbulence) create
different 'tunes'. It's sensitive to very low wind velocities ( < 10mpg).
Something like that (with electric guitar pickups?) might be feasible,
at least for a hobby project.

The possibilities here seem to be endless....

Mike
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2000\01\16@134534 by Sean Breheny

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Hey Mike!

It truely is a small world (or, at least, the PICLIST is a small world ;-)
I also play the tin whistle.

Sean



At 03:46 AM 1/16/00 -0600, you wrote:
>As a (very) amateur recorder and tin whistle player, I don't think a
>'regular'
>whistle like you find in the mouthpiece of a referee's whistle or musical
>instruments would work. They tend to put out a constant frequency until
>the air pressure reaches a certain level, then they 'pop' up to the next
>octave.
>

|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
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Personal page: http://www.people.cornell.edu/pages/shb7
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2000\01\17@032510 by Michael Rigby-Jones

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part 0 3596 bytes
<P><FONT SIZE=2 FACE="Arial">&gt;I guess that it could also be possible trying to keep SH_Temp few</FONT>
<BR><FONT SIZE=2 FACE="Arial">&gt;degrees above SC_Temp and using the microcontroller to do its job of</FONT>
<BR><FONT SIZE=2 FACE="Arial">&gt;some calculation and conversions. Lots of energy would be saved (at</FONT>
<BR><FONT SIZE=2 FACE="Arial">&gt;least in portable or battery operated units) when heating SH to -200F</FONT>
<BR><FONT SIZE=2 FACE="Arial">&gt;(instead +950F) when SC is at -300F.</FONT>
</P>

<P><FONT SIZE=2 FACE="Arial">Michael P Olson [SMTP:EraseMEbike_kulspamJUNO.COM] replied:</FONT>
</P>

<P><FONT SIZE=2 FACE="Arial">What about air density? It seems like I've seen something similar to this</FONT>
<BR><FONT SIZE=2 FACE="Arial">(constant current heater) used in the intake manifolds of automobiles to</FONT>
<BR><FONT SIZE=2 FACE="Arial">determine fuel injection settings. Would the heat transfer be the same at</FONT>
<BR><FONT SIZE=2 FACE="Arial">1,000 ft (300m) as it is at 10,000 ft (3,000m)? This may limit the unit's</FONT>
</P>
</UL>
<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">In EFI (Electronic Fuel Injection) terms, these are known as Mass Airflow Sensors, simply because they give an output proportional to the mass of air flowing through them.&nbsp; Therefore they are (or should be!) completely independant of the density of the air.</FONT></P>
<UL>
<P><FONT SIZE=2 FACE="Arial">You'd definitely need two sensors, both exposed I think. One could be</FONT>
<BR><FONT SIZE=2 FACE="Arial">'up wind' of the hot wire, one 'down wind'. This would make the finished</FONT>
<BR><FONT SIZE=2 FACE="Arial">unit a bit more compact.</FONT>
</P>
</UL>
<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">No, one sensor is shielded from the moving air.&nbsp; It has enough contact with the air to sense it's temperature, but is shielded from the possible effect of wind chill if the air was humid etc.</FONT></P>

<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">One feature of these sensors is that they will measure measure the airflow in either direction, although the output shows only magnitude.&nbsp; Not always a desirable porperty in EFI.</FONT></P>

<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">Older systems used the &quot;flap&quot; method, where a hinged and sprung flap was deflected by the air moving past it.&nbsp; The flaps angle, and therefore air velocity was measured by a potentiometer (which often wear out).&nbsp; This system does not take into account air density changees, therefore it is usualy used in conjunction with a MAP sensor (Manifold Absolute Pressure).&nbsp; The combination of these two sensors can measure true mass air flow.</FONT></P>

<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">Regards</FONT>
</P>

<P><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">Mike Rigby-Jones</FONT>
</P>

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