Searching \ for 'Weather Anamometer' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=weather+anamometer
Search entire site for: 'Weather Anamometer'.

Truncated match.
PICList Thread
'Weather Anamometer'
1996\06\04@103619 by Donald F. Wright Jr.

flavicon
face
I have been thinking about doing a little project using some PICs and could
use some ideas.  I will probably be using 84's and I am getting the PICSTART
PLUS on the 6th at the seminar.

About the project.  Having a cottage up on lake Huron, and owning a boat, a
good wind speed indicator and temperature readout is a welcome addition.  I
saw one in a recent issue of Sensor magazine and thought it would be fun to
build one.

The unit has no moving parts, but uses ultrasonics to detect wind speed and
direction.  The unit has four prongs with ultrasonic sensors on top of them.
There is a north-south path and a east-west path.  I then send out a pulse
from the north sensor, and time how long it takes to get to the south
sensor.  I repeat the process south-north, east-west, west-east.  This will
give me four times for the sound to travel the same distance.  I now will
have two vectors which can be added, a north-south vector, and a east-west
vector.  Then with a little trig., I can get the magnitude of the wind and
the direction.  I will then send out a variable frequency signal which is
the magnitude of the wind (0 pulses/sec is 0 mph to 100 pulses/sec is 100
mph, for example).  I was thinking about using a 8 bit number to tell
direction, but does anybody have a better idea?  Both of these will be
displayed on LCD's inside the cottage.

I also will monitor temperature with a transistor and will also display this
out on a LCD inside the cottage.  But the temperature will also activate
small heaters which will warm the ultrasonic tips to prevent icing in the
winter.  I have no idea where to start with some low power heating elements
to do this.

All the main electronics, PICs, etc., will be inside the cottage so
temperature there isn't a problem.

If anybody has any ideas, suggestions, or corrections to my design idea,
please respond.  Thanks in advance!


  Donald Frederick Wright Jr.

  School info: Lawrence Technological University
  E-mail: spam_OUTDW79208TakeThisOuTspamLTU.EDU

  Work Info: AVL North America
  E-mail: .....DNWRIGHTKILLspamspam@spam@AVLNA.COM

1996\06\04@120539 by 9 NPL, 2227

flavicon
face
Donald F. Wright Jr. wrote:-
<snip>
>The unit has no moving parts, but uses ultrasonics to detect wind speed and
>direction.  The unit has four prongs with ultrasonic sensors on top of
>them.
>There is a north-south path and a east-west path.  I then send out a pulse
>from the north sensor, and time how long it takes to get to the south
>sensor.  I repeat the process south-north, east-west, west-east.  This will
>give me four times for the sound to travel the same distance.  I now will
>have two vectors which can be added, a north-south vector, and a east-west
>vector.  Then with a little trig., I can get the magnitude of the wind and
>the direction.  I will then send out a variable frequency signal which is
>the magnitude of the wind (0 pulses/sec is 0 mph to 100 pulses/sec is 100
>mph, for example).  I was thinking about using a 8 bit number to tell
direction, but does anybody have a better idea?  Both of these will be
displayed on LCD's inside the cottage.

Possibly use grey code?

>I also will monitor temperature with a transistor and will also display
>this out on a LCD inside the cottage.  But the temperature will also
>activate small heaters which will warm the ultrasonic tips to prevent icing
>in the winter.  I have no idea where to start with some low power heating
>elements to do this.

Try using a TO220 power transistor in the linear region, to heat the
Ultrasonics. It could be called crude, but it is cheap, and the copper base
is ideal for mounting on the object to be heated (ie the US's). It have the
advantage that you provide a low power signal to the transistor - It's gain
does the rest. I used this for a robotics thesis recently, and it worked
like a charm - I used a Thermocouple and op-amp to stablize the temp at 36
deg C +/- 1/4 deg C, but you would probably not require any accurate temp
stablization, therefore no Thermocouple.

I would be very interested to see how well this project pans out, as I had
been planning a weather station, but with a wind vane and rotor. (never
thought of ultrasound!)

   Cheers
           Steve

1996\06\04@124105 by rdmiller

picon face
On Tue, 4 Jun 1996, Donald F. Wright Jr. wrote:
[...]
> The unit has no moving parts, but uses ultrasonics to detect wind speed and
> direction.  The unit has four prongs with ultrasonic sensors on top of them.
> There is a north-south path and a east-west path.  I then send out a pulse
> from the north sensor, and time how long it takes to get to the south
> sensor.  I repeat the process south-north, east-west, west-east.
[...]
> I will then send out a variable frequency signal which is
> the magnitude of the wind (0 pulses/sec is 0 mph to 100 pulses/sec is 100
> mph, for example).  I was thinking about using a 8 bit number to tell
> direction, but does anybody have a better idea?  Both of these will be
> displayed on LCD's inside the cottage.

You should only need *one* measurement in each of the two axis (N-S, E-W)
to get the wind vector.  Of course it would be wise to take multiple
samples and average them.  You could even have some indicator of the
*spread* of the min. and max. to get an idea of whether the wind is
"gusty" or "steady".

I'm not sure what the point is of that part about translating magnitude
into frequency, since you said you'd have all the electronics down inside
the cottage...

> I also will monitor temperature with a transistor and will also display this
> out on a LCD inside the cottage.  But the temperature will also activate
> small heaters which will warm the ultrasonic tips to prevent icing in the
> winter.  I have no idea where to start with some low power heating elements
> to do this.

You might do better to measure temperature with a 3-pin digital part
that would be a lot easier for your PIC to read.  Dallas Semiconductors
(http://www.dalsemi.com) makes some nice ones.

Low power heating elements could be done with nichrome wire (ask for a
"replacement heating coil" at your local hardware store).  You can get
the total resistance of the whole wire as R=(V^2)/P where V is the
rated voltage and P is the rated power.  Then chop off the proper
fraction of the coil according to how much resistance you need to
get your desired power output from your available power source.  If
a single element would exceed the rated current (P/V), then just put
multiple elements in parallel.  They'd have to be housed or embedded
to protect them from moisture and to prevent the possibility of fire.
I'd advise that you connect it mechanically since it may melt solder!!

Be careful.  Take precautions against *lightning* too.

Rick Miller

1996\06\04@130010 by Mike Keitz

flavicon
face
>On Tue, 4 Jun 1996, Donald F. Wright Jr. wrote:
>[...]
>> The unit has no moving parts, but uses ultrasonics to detect wind speed and
>> direction.  The unit has four prongs with ultrasonic sensors on top of them.
>> There is a north-south path and a east-west path.  I then send out a pulse
>> from the north sensor, and time how long it takes to get to the south
>> sensor.  I repeat the process south-north, east-west, west-east.
>[...]
>> I will then send out a variable frequency signal which is
>> the magnitude of the wind (0 pulses/sec is 0 mph to 100 pulses/sec is 100
>> mph, for example).  I was thinking about using a 8 bit number to tell
>> direction, but does anybody have a better idea?  Both of these will be
>> displayed on LCD's inside the cottage.
>
>You should only need *one* measurement in each of the two axis (N-S, E-W)
>to get the wind vector.  Of course it would be wise to take multiple
>samples and average them.  You could even have some indicator of the
>*spread* of the min. and max. to get an idea of whether the wind is
>"gusty" or "steady".

The speed of sound varies significantly over temperature (it also varies
with pressure/altitude, though maybe not enough over the range of pressures
encountered in a fixed location to worry about)  Either the temperature
reading needs to be factored into the computation, or soundings taken in
opposite directions and the *difference* attributed to wind speed.  The
opposite directions method is probably more accurate at low wind speeds, and
the only one guaranteed to read zero when there is indeed no wind.  It also
wouldn;t be affected by pressure.  But the temperature correction method
should also be considered, as it is likely to be best at high wind speeds,
when variation of the wind vector during the time between readings in
opposite directions could be substantial.

I belive there is a prescribed method for averaging wind measurements in the
meteorolgy field to produce the two reported mumbers of wind speed and gust
speed.


>I'm not sure what the point is of that part about translating magnitude
>into frequency, since you said you'd have all the electronics down inside
>the cottage...

It would save on cost of the cable to put most of the electronics at the
sensor, at least to the point of converting all raw measurements to serial
digital data.  The averaging and final math would be done in the display
unit, which is likely to require a processor a bit more than a PIC anyway.

{Quote hidden}

[...]
Just use an ordinary power resistor, even better one of those aluminum-cased
ones which is already made to bolt to a surface.  If the object is only to
prevent icing, simply turn the resistors on when the temperature reading
nears freezing.

-Mike

1996\06\04@132116 by Kalle Pihlajasaari

flavicon
face
Hi Donald,

> The unit has no moving parts, but uses ultrasonics to detect wind speed and
> direction.  The unit has four prongs with ultrasonic sensors on top of them.
> ....
> displayed on LCD's inside the cottage.

Nice sensor, remember to ignore values that have a large delta comapred
to previous readings, you may be measuring rain or hail effects.

> I also will monitor temperature with a transistor and will also display this
> out on a LCD inside the cottage.  But the temperature will also activate
> small heaters which will warm the ultrasonic tips to prevent icing in the
> winter.  I have no idea where to start with some low power heating elements
> to do this.

You could use a Analog Devices TMP-03 (-04) device to measure temp
with one PIC pin. See my page

http://www.ip.co.za/people/kalle/project.htm#heat

A Wire wound resistor is also a simple heating element and you could
get 4 of the same and wire them in series with one temp sensor on the
back of one prong and then you would have the same amount of heat
on each prong with a feedback mechanism to keep them above freezing.
Another temp sensor would be required to measure the ambient.

> All the main electronics, PICs, etc., will be inside the cottage so
> temperature there isn't a problem.

Beware of long wires for Sonar pulses and heater currents unless you
use quality cables.  You might want to put one controller outside
and only have one power cable up and one comm cable down.

> please respond.  Thanks in advance!

Welcome

Cheers
--
Kalle Pihlajasaari     kallespamKILLspamdata.co.za
Interface Products     Box 15775, Doornfontein, 2028, South Africa
+27 (11) 402-7750      Fax: +27 (11) 402-7751

1996\06\04@134202 by Roger Books

flavicon
face
>  >You should only need *one* measurement in each of the two axis (N-S, E-W)
>  >to get the wind vector.  Of course it would be wise to take multiple
>  >samples and average them.  You could even have some indicator of the
>  >*spread* of the min. and max. to get an idea of whether the wind is
>  >"gusty" or "steady".
>
>  The speed of sound varies significantly over temperature (it also varies
>  with pressure/altitude, though maybe not enough over the range of pressures
>  encountered in a fixed location to worry about)  Either the temperature
>  reading needs to be factored into the computation, or soundings taken in
>  opposite directions and the *difference* attributed to wind speed.

This doesn't sound right.  It looks like you need to factor in speed of
sound differences/temperature even going both ways.

If the speed of sound in 40 degree air is 100 units/sec, and in 20 degree
air is 200 units a sec, then:

       40 degrees - 100 units/sec
     1 unit/sec wind  ----->     sender    100 units distance   receiver

 The transit time is roughly .99 seconds.  The return trip is roughly
1.01 seconds.  The difference then is .02 seconds.  So far so good.  Now

       20 degrees - 200 units/sec
     1 unit/sec wind  ----->     sender    100 units distance   receiver

 The transit time is roughly .495 seconds.  The return trip is roughly
.505 seconds.  The difference is .01 seconds.  Same wind speed, different
temperature.

 I realize my numbers are not quite precise (Since the transit time downwind
is less than a second you will not get a full extra unit in the time, etc
etc) and the example speeds are extreme, it is just to demonstrate the
problem.

If there is a flaw in my math feel free (as if the list wouldn't) to correct
me.

Roger

1996\06\04@150033 by Scott Newell

flavicon
face
Hi, I thought I'd hop in a maybe embarrass myself with a simple algebra
error or two.


Ok, let's assume that we have:

d = distance between ultrasonic sensors.
w = wind speed
v = speed of sound
t1 = time for left to right transit
t2 = time for right to left transit

(I'm gonna do the math assuming a positive wind speed means left to right; a
negative wind speed would then mean the wind is traveling from right to left)

From left to right, we get

d = rate * time
   rate = w + v        ; I'm assuming the + wind is also from left to right
d = (w+v) * t1
d/t1 = (w+v)            ; we're gonna use this again, in a minute


Now, from right to left

d = rate * time
   rate = w - v        ; since we're going against the wind
d = (w-v) * t2
d/t2 = (w-v)            ; compare to above, this is the important part


Now, we can subtract.

(w+v)  -  (w-v) = 2w     ; there goes the speed of sound and temperature
(d/t1) -  (d/t2) = 2w

w = 1/2 ((d/t1) - (d/t2))


or, continuing on,

    1      (d * t2)        (d * t1)
w = ---  *  --------   -    --------
    2      (t1 * t2)       (t1 * t2)


    1       d * (t2 - t1)
w = ---  *  --------------
    2         (t1 * t2)


    d       t2 - t1
w = ---  *  ---------
    2       t1 * t2

Since you're gonna build the thing, you'll know the distance at compile
time.  Measure the transit time in both directions, and forget about the
speed of sound.



later,
newell

1996\06\04@162404 by fastfwd

face
flavicon
face
Scott Newell <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU> wrote:

> Hi, I thought I'd hop in a maybe embarrass myself with a simple
> algebra error or two.

   You did:

> (w+v)  -  (w-v) = 2w

   Actually, it's the left-hand side of that equation that's
   wrong... The second term should be "v-w", right?

   -Andy

Andrew Warren - EraseMEfastfwdspam_OUTspamTakeThisOuTix.netcom.com
Fast Forward Engineering, Vista, California
http://www.geocities.com/SiliconValley/2499

1996\06\05@130056 by nigelg

flavicon
picon face
In message  <9606041855.aa22724spamspam_OUTdevice.data.co.za> @spam@PICLISTKILLspamspamMITVMA.MIT.EDU
writes:

> > The unit has no moving parts, but uses ultrasonics to detect wind speed and
> > direction.  The unit has four prongs with ultrasonic sensors on top of them.
> > ....
> > displayed on LCD's inside the cottage.
>
> Nice sensor, remember to ignore values that have a large delta comapred
> to previous readings, you may be measuring rain or hail effects.
>
> > I also will monitor temperature with a transistor and will also display this
> > out on a LCD inside the cottage.  But the temperature will also activate
> > small heaters which will warm the ultrasonic tips to prevent icing in the
> > winter.  I have no idea where to start with some low power heating elements
> > to do this.

A small British company developed these type of anemometers for use on
sailing yachts. It was shown on the TV program 'Tomorrows World' a few
years ago, they won a LARGE! competition run by British Gas to design
a new gas meter. They used the same technique to measure gas flow through
the meter.

Nigel.

         /----------------------------------------------------------\
         | Nigel Goodwin   | Internet : KILLspamnigelgKILLspamspamlpilsley.demon.co.uk |
         | Lower Pilsley   |                                        |
         | Chesterfield    |                                        |
         | England         |                                        |
         \----------------------------------------------------------/

More... (looser matching)
- Last day of these posts
- In 1996 , 1997 only
- Today
- New search...