Wind Speed Annometer

So I have a few old hard drives lying around and thought that because of the smooth spinning it would make a great wind speed meter for my Weather-station.I took a resistance reading using a meter set on 200 ohm scale and found these readings all in ohms:

1-2 1.0
2-3 1.9
3-4 1.9
4-1 1.3
1-3 .9
2-4 1.7
How can I use these to create a sort of encoder i guess to give me relative wind speeds . of course I still would have to connect some sort of vane to the motor to spin the motor. I would like to use my Arduino Uno to calculate the motor turns .

Some anemometers use brushed D.C. motors as generators, with an output voltage proportional to wind velocity.

A hard drive motor would generate A.C. current, which an Arduino can't measure without external circuitry.

Understood but it still could it still be done with other circuitry, it just seems like such a nice way to get speed measurements with this smooth rotation and not have to construct a anemometer bearings and such.Thanks for the quick reply

You sound a little confused. You are certainly confusing me! Are you planning to build an anemometer or a windvane? Do you understand the difference?

Yes I mis spoke, all I want to do is calculate the speed of the wind and send it to Things speak using the ESP8266 Wifi device. Thank you for correcting that .

No problem.

So what was the table of resistances and "points" about? I didn't understand that. Do you plan to measure the voltage generated by the anemometer spinning the motor, or count the revolutions by monitoring the changes in resistance?

PS. Here is my WiFi weather station, in case it's interesting for you.

So that is where I am confused , don't know how to calculate or use the information I can get from the motor.I assume (I know it is never good to assume anything) I could just get some sort of reading from the motor winding and extrapolate it into some useful data,weather it be making and breaking pole or generating a voltage. Just was hoping that some one may have already done something with this type of device.Thanks again,seems I got your ear LOL

Paul, just looked at your weather-station, nice job,did you construct the vane and windspeed detector?

Well, once you attach cups to the motor and the and wind spins it, it will start to generate a voltage. Trying to measure the coil resistance in those circumstances won't be a good idea. So measuring the voltage generated may be the better plan.

Suggest your first steps should be to attach some cups, however you plan to do that, and hook the motor terminals up to your multimeter (on AC voltage scale) and see what sort of result a stiff breeze produces. This may involve a desk fan!

Thanks , kinda of where I was heading , just confused as to what I would be measuring,why I wrote the readings.So I will set it up so I can generate a constant speed and start checking what I get from the leads, any suggestion as to which leads I should check.Trial and error seems the best way,just don't want to kill my arduino LOL .Thanks again for the guidance and information as to the AC voltage that could get I have to think if I can somehow use this voltage, see off on a tangent again.

The anemometer and windvane are/were sold by Maplin as replacement parts for the inexpensive consumer weather stations they sell/sold. Time is running out if you want to buy them, assuming you live in the UK. The "mast" I built from plumbing 22mm overflow pipe parts.

Thanks, I used to work at McAlpins as a maintenance manager here in the US , it is a sheet metal plant.made automotive parts and other fabrication, I know not the same company, just Ironic i guess.

Some anemometers use brushed D.C. motors as generators, with an output voltage proportional to wind velocity.

A hard drive motor would generate A.C. current, which an Arduino can't measure without external circuitry.

The HD motor is a DC motor.

Be sure to get the crescent supermagnets and cage or if you can get the whole voice coil out it'd make one heck of a servo.

There are videos and sites covering HD hacking and salvage. See if brands make much difference on the inside as to what pin does what. I've seen video where the guy hacked servo and disk motion but since I haven't I can't give you good instructions but search!

The disk is shiny right? If you can black out spots on the disk, a led and detector can read them as non-reflective and you can get RPM from that while the drive bearings do their stuff. If the speed changes much, don't just put 1 or 2 spots on the platter, Arduino can watch even small spots go by over several digital reads.

The HD motor is a DC motor.

Most platter motors, if not all, are brushless and when spun, the windings generate an AC voltage.

This is actually simple.
Attach your veins so that it can spin.
Paint some white out on one place on one of the platters
Getting IR transmitter / sensor and count how many revolutions per minute.
You can get pulse in on any digital pin on your Aquino.

Use of a multimeter checking for AC or DC volts can save you an Arduino and a lot of headscratching.

Output DC = voltage divider.

Output AC = bridge rectifier, followed by small capacitor, followed by small discharge circuit, followed by voltage divider.


Attach your veins so that it can spin.

I think you mean "vanes".

I am sure that the super-nice HDD bearings would last at least 30 minutes outdoors in the rain.

This is one of those problems that appears easy but is actually hard.

Might put the wind cups on the outside edge of a disc shaped plate that also covers the sealed bearings?

You can buy really good bearings now but there's just something about free if it can work that gets necessity into play,
and necessity is the mother of invention, a mother indeed!

Can you post a picture of the HD motor assembly please?

Thanks.. Tom.. :slight_smile: