Hi my group project is about designing and simulating a PWM fan controller and we have already come up with a circuit, which produces a square wave as an output and we can also change the pulse width changing the threshhold.
But we also have to include a simple model for the motor to see how it behaves (reistance, inductance) and I don't know how to where to find one.
Moreover I would like to be able to calculate the speed @ which it rotates, but I dont know how to do it. could somebody please refer me to good webpages or come up with a solution, because i have been trying but could not find anything.

Thank you

VVS

 

have you tried using a tachometer?

or maybe this can help

 

we are not actually building the PWM we are just simulating it in PSPICE and we are wondering how to model the dc motor in the output and what values to use for the components of the model?