Wireless windmill revolutons counter

Hi Everyone,

I am looking to count the revolutions of a small windmill and monitor or read these counts without wires a(RF or wifi). The switch will be custom and isn't really in question, but to tie it in with an Arduino with some sort of wireless module that is battery powered is my real challenge.

NOTE: The reason for battery/wireless is so that the wind can change directions and I don't have to worry about wires wrapping around the mast. I could put everything in a weather proof prject box and mount it on the free-moving part of the windmill.

Open to any ideas, suggestions!

Thanks in advance,


Have you considered slip rings?

Thanks Riva, I had considered something along these lines however the top part balances on a large pin. If I end up not being able to do this via wireless, I'll alter the pin apparatus to be hollow and go with your suggestion. I never knew what they called these, so thanks again :slight_smile:

There is no reason you can't do it wirelessly. A magnetic encoder should do the trick. You can mount the magnet to the spinning part and mount a hall-effect or similar encoder to the mast, and it will cause a signal every time the magnet goes by. As to making it wireless, that's a separate and well documented issue. You have bluetooth, wifi, and various RF modules to choose from. However, my recommendation doesn't involve needing it to be wireless, since you mount the wired stuff to the mast and it doesn't move.

Just look up magnetic Rotary Encoders.

Thanks Mirith, that sounds like a great alternative to a contact solution I was thinking of. As far as the mast, I should clarify that I am referring to the mast as the vertical part of the windmill where the pin is, the top horizontal part I'll refer to as the boom (for lack of better word). The magnetic encoder would be on the end of the boom by the blades itself, but the boom still needs to be able to rotate 360 independently with the wind direction on the stationary mast's pin (sorry I wasn't clear on that). The transmitting unit would sit on the boom, presumably in the middle to maintain balance.

Now that you've laid down some of the wireless possibilities (bluetooth, wifi, RF) I suppose an after-thought consideration would be battery life; assuming the windmill could possibly transmit 60 times a second minute. Maybe it might be more efficient to transmit an RF beacon so to speak, between 2 boards as opposed to maintaining a wifi or bluetooth connection?

Again, thanks everyone for your input. A seemingly trivial project to most but an interesting one for my family :slight_smile:

Do you need to transmit/update that often? I could see a more reasonable time being every 10s/60s/5min depending on what you are doing with the data. The Arduino can just store the data and transmit it on request.

Since you put it that way, I can't think of any reason why it would need to update every rotation/count. Since we're not after time based precision, we could sample once a min (most likely hour) and do RPM math on the computer side. I suppose our main goal is to see the life-time revolution counts as they increase, and stats such as RPM with a time-stamp just a curiosity.

you might add a small solar panel to the setup to keep the batteries (lipo?) filled.

Why bother with the windmill if you need solar panels?


What kind of windmill is this? If the regulator isn't inside the windmill then you should be able to watch the AC waveforms in the lines out from the windmill to measure RPM.

Its a small hand-made windmill (blades are roughly 1 foot, ~2 feet diameter span), made out of cedar shingles and a simple bearing to hold the fan blades on. The boom is made out of PVC and the tail fin thin aluminum. The center of the boom is a PVC 'T' that sits on top of a nail or pin to allow the boom to turn with the wind.

So far, I'm going with Mirith's suggestion on the hall effect sensor. The part I need to wrap my head around are the components needed to transmit (whether the data is pushed or pulled) via wirelss. I currently only have an UNO card that came with the starter kit, but willing to get whatever is needed; maybe try a few different ways. The range to the computer is roughly 20 feet line-of-sight but through a window.