Deep_Sky:
As I wrote the Rotary Encoder using to increase and decrease the value which sets the speed of Fan
So it is just being turned by hand? I thought it might be turned by the motor and be used to measure speed.
Could you please clarify the function of particular library?
The problem is with reading the frequency of RPM, not driving of Fan
I had assumed the name would convey all that is needed - it just works faster than the standard digitalRead() so it should ake more CPU cycles available for other stuff.
Alas :), you have not responded to the important part of Reply #1 - how are you detecting the speed?
...R