hallo everybody,
I want to control rpm of dc motor. I use little 12 V dc motor for cassette player. I use it to stir a jar filled with emulsion. Unfortunately the viscosity of emulsion is not constant. Now i'm looking for required voltage to supply the motor. I need to stir with speed of 60-100 rpm. I've tried to give 3V to the motor. At the begining it seems good. But when the emulsion is thikened, the motor is stopped. The idea is, when i find the required voltage then i give a PWM code to drive the motor. Should I install an encoder to controll the speed? Or do you suggest to use current sense? I have measeure the motor current. Zero load current: 1.5V->26mA,3V->48mA,6V->89mA,7.5V->103mA,9V->116V,12V->138V.Current when the motor stopped (to much load): 1.5V->38mA,3V->88mA,4.5V->140mA,6V->178mA,9V->230mA,12V->138mA.I wonder if I use a comparator to detect if overload is happened. But comparator limit will depend on motor voltage, then the circuit will be complicated.
Any suggestion ? Thanks a lot and sorry if I make a ridiculous question, I'm a beginner in this.