DC motor transfer function

[yifei87]

I m working on a project and i would like to obtain the transfer function of dc motor.
i m using an encoder since i cant find tachometer.
however, i have no idea how to use it?
can anyone teaching here? thank you very much

[madhephaestus]

If you have a microcontroller that has a timer and an external int interrupt you can determine the velocity of the motor. You start the timer when the encoder ticks, then stop it when a known amount of ticks from the encoder have counted up. Read the timers count registers and you can calculate angular velocity. Over that same period of time you can measure current draw using a .5ohm resister in series with the motor and throwing an ADC across it. This will give you energy in in relation to velocity over time. I think thats all you need to plug in and get your transfer functions. Setting up all of these things on a microcontroller can be difficult and varies from chip to chip, so plan on spending a lot of time with your chips data sheet.