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# Reed switch wind speedmeter? Answered

Hello, I need some help with counting the pulses  on digital pin with reed switch and arduino for speed meter and also calculation for the speed in km/h.

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## 8 Replies

May I suggest you use a Hall Effect Sensor instead? Much more accurate, with no delay ! (Still uses the same concept though)

Create a Var that will store how many rotations happen in a set time. (X = X + 1)

Then create a timer that will take how many rotations happened in the set time and store at least to 3-5 Values ( 3-5 so you can average wind speed; it will be less erratic) As new values are created they will overwrite to oldest one.

That will give you the Rotations Per Minute of the shaft.

From here there are two ways to proceed.

A) *This is what I would do* Buy a Calibrated "anemometer" (Wind speedometer) that will tell you what wind speed produces what RPM. Then it's just simple conversion(s) to find the Km/h.

or B) Build your own and callibrate how many rotations happen at a set wind speed. (Eaiser said then done)

Konstantin Dimitrov (author)2015-08-26

Yes, it worked thanks !

FarmerKJS (author)2015-06-15

Over to the left there is a bike speedometer. You could probably use that.

https://www.instructables.com/id/Arduino-Bike-Speedometer/

Konstantin Dimitrov (author)2015-06-15

No, I checked that, but it wont do the trick.

Wired_Mist (author)2015-08-25

Thanks for the BA, Did it work out for you?

verence (author)2015-06-15

Why? It's just what you need.

steveastrouk (author)2015-06-15

+1

rickharris (author)2015-06-15

a really easy way to do this is to use a cycle computer. Arrange the magnet to be blown round by the wind and measure the speed as if it were on a bike wheel.