Speed calculation slow motor

Hi dear,

I ask you help.I must calculate low motor's speed.He go around by 20 to 177 cm minute. How i can calculate is? i try with magnetic sensor but i have bad result.Please, suggest my a code and sensor

Sorry for by bad inglish and thanks for help.

Francesco

What are you looking for exactly, RPM, FPM, FPH, MPH or KPh?
This is your RPM, "20 to 177 cm per minute"
FPM (feet per minute) = diameter of wheel * 3.1415 * RPM
FPH (feet per hour) = FPM * 60
MPH (Miles per hour) = FPH / 5280
KPH (Kilometers per hour) = MPH * 1.60934

i looking for Centrimetes/Minutes but if you can give me another misure i can convert it

RPM, "20 to 177 cm per minute" = Centimeters/Minutes

the range of motor speed start 20 cm per minute and end to 177 per minutes.How i calculate the speed to show in arduino?

What speed? Feet per minute, miles per hour, kilometers per hour, I gave you all the calculations.
If your asking how to actually code it, then you will need some kind of sensor. Either a distance sensor from a fixed point, or a rotorary encoder attached to one of the wheels. You can even use IR as a speed gate. Take your pick.

i need RPM speed and i use a rotary encoder. i search a code

“google arduino rotary encoders” gave me a lot of information including code e.g. - http://playground.arduino.cc/Main/RotaryEncoders -

It is probably not what you are looking for but should get you started,