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Making a wind sensor

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xcfisher

New Member
Ok guys, bear with me here. What I'm "trying" to accomplish is this:
I need to make a very small wind sensor that operates a linear actuator at a certain wind speed. I'm not an electronics expert, but I'm learning, so any help would be greatly appreciated!
Also, the linear actuator needs to be very small, does anybody know where to find one? It only has to be able to lift around 1lb or so of weight, nothing heavy, but speed would be great.
thanks.
 

nettron1000

New Member
A suggestion: Use a wind turbine ( propeller) to drive a small generator and use a comparator circuit as a voltage level sensor which will activate a relay at a set voltage level.
 

jem

Member
A wind sensor is generally made by sensing the change in resistance of a wire dissipating a controlled amount of heat. Take a piece if Nichrome or other resistance wire, and pass a constant current through it so that the wire heats up to somewhat above ambient. Use this wire as part of a wheatstone bridge. Actually, the whole bridge can be driven by a constant voltage if the other resistors are precision, low tempco components. The amount of unbalance in the bridge then reflects the wind velocity. The higher the wind velocity, the smaller the temperature rise in the sense wire, and the lower the resistance of the sense wire.

As for the actuator, at one point Jameco was selling "muscle wire", which pulls when an electric current flows through it. The current is fairly substantial though (about 1 - 2 A). You might want to check this out instead of a linear travel, or solenoid actuator.

Jem
 

xcfisher

New Member
nettron1000,
that is a great idea! Thanks for the help.

Jem,
do you know how much weight the "muscle wire" can pull?

As a side note, all of this needs to run off of a small sealed battery, the smaller the better like 9v size... any suggestions on something that would last a long time, and work outdoors?
 

jem

Member
Check this out. Muscle wire require fairly large currents, but at low voltages. If you need intermittent pulling operation, you can conceivably use a supercapacitor to deliver the large current pulse while draining a smaller current longer-lasting charge current.
 

xcfisher

New Member
here is the problem im running into.
Basically, I need to make something that operates like the flap on an airplane. It needs to open the flap, and keep it at that position until the wind speed is decreased, and then drop the flap back down. I was thinking about a linear actuator, or a solenoid, but I dont know if it can hold the force of a high wind speed on the flap, for a relatively long period of time.. the duty cycle would have to be 100%, and something like that is expensive to purchase... I was also thinking about some small pneumatic, or hydraulic cylinders, but I'm not sure how to open/close those electrically... I'm stumped!? :?:
 

jem

Member
You would probably need to consider a servo motor, or a stepper motor. Both require some control circuitry. If your torque needs are modest, you can probably salvage one from an old diskette drive.
 

Klaus

New Member
OK, here's another idea. But, you did not tell us at what exact windspeed you want the flap activated, the following might work only for faster wind speeds.
What you do is mount some centrifugal weights on a wind turbine shaft. A bit like the ones you see on the centrifugal start/run switch of inductive single phase motors.
If your wind speed is sufficient, the centrifugal movement of the weights will do the work for you. Either via a plate and a sliding lever or a hollow shaft, to activate the flap.
This will need no electricity at all, a purely mechanical solution to your problem. No batteries to go flat either :wink: .
Now, tell me *eactly* what you are building, I'm intrigued :) .
 

xcfisher

New Member
klaus, I like your idea, but im not sure how I'd work it into my application. What im working with is a carbon fiber Spoiler that has a small flap which is raised at high speed, say anything over 50mph... if you are familiar with the Porsche 911,996 you know what Im talking about. It needs to raise, and then be able to lower after the speed is slowed. The flap needs not raise more than 45 degrees from flat, so we arent talking about a huge distance, but it needs to be suffeciently supported so the wind will not just blow it back down! Hope this stirrs your creativity :wink:
 

Klaus

New Member
Ah, you are talking about an entirely different wind here :wink: , usually referred to as 'slipstream'. A wind sensor would be not the best idea for this since the wind is 'apparent wind' that changes with vehicle speed and wether the vehicle is driving in a head or tailwind.
You could, theoretically, experience no wind at all while doing 60mph if you are happen to do that in an equivalent tail wind.

You might be better off picking up the trigger signal from some speed sensing device, perhaps you could fit an optical sensor to the final drive and use the output of this to activate your flap drive.
Now, if I get that right, the idea of a spoiler is to create downward pressure at speed. The flap would be there to fine tune that pressure. There might be a condiderable load on the flap so whatever drives it has to be able to stand up to that. Perhaps a worm gear drive? Good input to output power ratio, low output speed so you could use a small DC motor to drive it and, best of all, it stays put where it is if the power comes off. So, you gradually drive the flap up as the speed sensor increases its signal and drive it back to neutral as the speed drops.
You can find worm drives in hobbyist shops, perhaps they have a suitable one.
Its a bit more complicated than you wanted but I cannot see a solenoid do that job as reliable without being quite bulky. Also, solenoids are either on or off, no in between as the above drive allows.
 

xcfisher

New Member
Klaus,
I figured that MIGHT be a problem to deal with.. your right, the speed would probably be the better idea. I could just use a crude bicycle speedometer hooked to the rear wheels, that would do it. However im not sure about the circuitry btw the sensor and the worm drive motor.. but it's a start!
 

Roff

Well-Known Member
If you're going 60mph with a 60mph tail wind, it seems to me that your spoiler will have no effect, and in fact you probably don't need any effect. Isn't "air speed" the important factor here?
 

carte106

New Member
Wind Sensor

A wind sensor is generally made by sensing the change in resistance of a wire dissipating a controlled amount of heat. Take a piece if Nichrome or other resistance wire, and pass a constant current through it so that the wire heats up to somewhat above ambient. Use this wire as part of a wheatstone bridge. Actually, the whole bridge can be driven by a constant voltage if the other resistors are precision, low tempco components. The amount of unbalance in the bridge then reflects the wind velocity. The higher the wind velocity, the smaller the temperature rise in the sense wire, and the lower the resistance of the sense wire.

Jem, I am curious to know the availability of this type of set up. Are there any basic units that can be bought? Or would I need to build this in the garage.
 

tcmtech

Banned
Most Helpful Member
You are about 7 years late for the party. The last post was done in 2003.
 
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