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Ok fellas I'm a newbie to the electronics hobby and I enjoy messing with dc motors.
I haven't jumped into building my own motor controllers yet but hopefully soon. But my question is, if I have a 6v-90v pwm
Do I need a 90v power supply to get the max pwm?
PWM is not a voltage, instead it is a duty-cycle. If the pulses of PWM duty-cycle are near 100% then the motor will have lots of power and spin fast if the power supply produces near the maximum allowed voltage for the motor. But if the pulses of PWM duty-cycle are near 1% then the motor will still have a fair amount of power but it will spin slowly if the power supply produces near the maximum allowed voltage for the motor. If the power supply voltage is less than the maximum allowed voltage for the motor then the motor will not have much power.
If you apply the maximum allowed voltage to your motor and run it at or over its power rating and it has no cooling then it will curl up and die soon. Read the fine print about heat and how to cool it in its datasheet.
My electric radio controlled model airplanes have a very small motor that produces a lot of power. Flying, the motor has forced air cooling but it gets very hot and the manufacturer recommends full power for short durations and letting it cool down before it flies again. Of course, PWM is used for its speed control.
If you want to go from 0% (full-off) to 100% (full-on) PWM duty-cycle, here's a fairly simple circuit that will do that.
It will need to drive a MOSFET of the appropriate voltage and current rating to control the motor.