Wind Sensor

snipped-for-privacy@gmail.com wrote in news:51da9b37-2e9c-453a-8b96- snipped-for-privacy@googlegroups.com:

Find the radios to the center of the cups and fins circumference, say in inches. That is what it travels per pulse. Count the pulses per minutes = total distance in min., then convert to foot, mile and hour, that is your mile per hour wind speed.

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Take it for a ride in the car!

I already did the car ride.I want to do it in the lab. with the DC fan. It would be so cool. Any solutions!

When there were projects like this in the hobby electronic magazines, it was pretty standard to tell the reader "take it for a car ride".

Michael

I doubt you can without any ducting. Even with that I doubt it could be done without lots of work.

One thing you could do is get another calibrated wind speed gauge and see how much/fast the air is moving.. You would have to make sure the cups are full of wind air to be valid.

John,

That fan is not going to give enough velocity to be of use.

Confined to a tube 40cm in diameter, Determine cross-section area in sqft = 1.396263sqft Invert area to determine the length required to equal 1 cuft = 0.716ft

25.6 of these passes thru every minute = 18.33FPM *60 per hour = 1100FPH /5280 per mile = 0.21MPH

or ignore the size and convert 25.6 FPM to MPH = 0.29

25.6 x 60 / 5280

Scott

One of the requirements for the controller circuit for this motor...

was to be able to get it started in the proper direction when wind had

cabin blower).

I tested it using my leaf blower ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
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I love to cook with wine.     Sometimes I even put it in the food.

You want to use the fan to calibrate it? I don't think there will be any good conversion. It will depend on how the air can spread out. How close they are to each other. You could make some sort of wind tunnel to keep the air flow constant, and then drop bits of paper into the stream and measure veleocity with a video camera.. .but that sounds like too much work.

George H.

ND/2356497

Your fan is _rated_ at 25.6 CFM, but will _actually produce_ lots of different flows.

Do you have a car with a spedometer? Can you put together a lash-up that'll work in the car? Do you have any friends?

The classic 20th century amateur method for measuring wind speed is to take your anemometer out on a calm day and drive around, comparing readings between your spedometer and your anemometer. Preferably you'll pick a stretch of road and drive back and forth, to more or less cancel out the effects of wind.

Cars are a great resource for investigating aerodynamic problems that occur at or below the speed limit.

--
www.wescottdesign.com

You are right. I have already driven around in the car. I just wanted to do in the lab.

The only alternative that I can think of off the top of my head is to get a reference anemometer, or maybe to somehow make a positive-displacement pump.

I think to be really controlled you'd need it to be in a wind tunnel, BTW. It depends on how accurate you need to be.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com

I wonder if mass air flow sensors, basic ones, used in places like engine intakes would be enough?

Following this thread I am kind of curious as to what the real objective is?

At one time we made a mass air sensor to detect the presents of air flow in a exhaust system that is high in ozone. This environment is toxic to even basic air flow detectors fail in short time.

So we got some very fine bronze wire and made 3 terminal balanced loop to fit inside the exhanst (Half bridge), one half of the loop sitting near by unexposed to the stream while the other exposed. Used a basic comparator, calibration circuit and I think about 100mA of current in the loop. Even with the wire inside getting covered with nitric acid it seems to hold up well. The concentration of HNo3 is not at that location, so the loop does not get abused much.

At the bench, while testing this little gem, I was able to detect air movement via people walking in/out of a sliding door that is ~ 50 feet away. of course we are talking about a loop that is ~ 6 feet high and 3 feet wide on the sensing side.

I am not sure if such a method could be used for accurate speed measurements.

But like I said before, we don't know the objective of work here.

Jamie

I am learning how to interface the wind sensor and accelerometer to a micro controller. I figured out the wind sensor with micro by driving the car ar ound. I build an interrupt routine to detect and count the pulses coming ou t of the wind sensor. It's working fine.

I just thought may be if I can convert the CFM to miles per hour and use DC fan then I might be able to improve the code in the lab, look cool and sav e some money on gas.

I am using ADXL345 Accelerometer. It generates voltages on all of its three axes. I am little confused about calculating the tilt with the help of vol tages on its three axes.

For example the following first paper talks about really complicated ways t o calculate the tilt

-1057.pdf

and this second paper talks a little differently ( see " Examples Calculati ons")

I am confused which approach should I follow.

John

I'm pretty sure that that fan hasn't been calibrated to 25.6 CFM, that's just what was measured in some test setup.

Blow some smoke into it, and take a video, examine frame by frame (or use a chronograph) to determine 11speed.

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  \_(?)_

on a windless day, at the end of a long pole to advoid the venturi effect.... BTBT,

I recorded the output pulses, and voice commentary, on a portable casette recorder and analysed it on a pc afterwards.

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  \_(?)_

start by building a wind tunnel, use cardboard, lexan, whatever... duct tape seems apt :)

then inject some smoke and see how fast it moves. Assume that the smoke moves at the same speed as the wind.

Place your sensor in the clear air in the centre of the tunnel.

--
  \_(?)_

I imagine one would need to extend the sensor on a pole, well out from the body of the car (maybe 1-2 feet), to get readings such that air speed corresponds to vehicle speed.

Close to the body, there will be all sorts of issues from turbulence and Bernoulli effects. (All that air that impinges on the frontal area of the car has to go somewhere!)

Best regards,

Bob Masta DAQARTA v8.00 Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, Pitch Track, Pitch-to-MIDI FREE 8-channel Signal Generator, DaqMusiq generator Science with your sound card!

For $12.99, you can buy this to calibrate your wind source:

Can you advise how can I use this Anemometer to calibrate the Wind Sensor?