Using Arduino with propellers

What sketch would you use to get the results of the number of turns a Brush-less dc 5v motor will turn every minute.

Tachometer code might be of use, but you may need to figure out how to detect a rotation.

https://www.google.com/search?as_q=tachometer&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=http%3A%2F%2Fforum.arduino.cc%2Findex&as_occt=any&safe=images&tbs=&as_filetype=&as_rights=

5V brushless motor? What an odd voltage for a motor, they are usually on the 3/6/12/24/36/48V series (if sensored) or a whole number of LiPo cells (for RC style).

Do you have a link for this mysterious beast?