Anemometer

Also know's as a windspeed meter. 

I use an harddrive motor as encoder. The bearings are very good.  

Still working on it, but i tested the motor with the electronic's and that look's promissing.

                                                     Mechanical drawing (topview)

The motor generate's 3 pulses per revolution. The motor consist of 3 winding's and generate's an

3 phase sinus on it's coil's.

I only use one coil which is measured with an comparator with feedback. 

A oneshot is used to give pulses with a steady width so it's easy for an microcontroller to measure.

                                 

Test setup 

I used drain pipe end cap's to mount the motor and also to protect it against rain.

Violet trace: output from the motor

Blue trace:   output from the comparator

Red trace:    output from the Oneshot.