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Homework Help: Controlling motor speed

  1. Apr 5, 2006 #1
    I need some help on lab questions....

    a short description: we are using Pulse Width Modulation (PWM) module of a 68hc12 microcontroller to control speed of a motor hooked up to the microcontroller; the potentiometer connected to ATD channel provides a DC voltage that is sampled using ATD module which determines the duty cycle of the output pulse wave, and based on the settings of the PWM registers, that pulse wave is driving the motor at a set frequency.

    So the question is: what are the advantage of using PWM vs other alternatives?

    All i can think of is function generator, what could other alternatives can drive motor?
    And as far as advantages, well... it allows one to set the frequency and duty cycle, and generate interrupts stuff like that..... is there something i am missing?
    Thanks in advance....
  2. jcsd
  3. Apr 6, 2006 #2


    User Avatar

    Staff: Mentor

    Here's a recent thread from the EE forum that will help you out:


    Also, when thinking about this problem, remember what you are driving in the motor. When the rotor is stopped, the value of inductance and impedance is very low, right? What is the drive impedance at full speed? So what is it in between?
  4. Apr 8, 2006 #3
    oh, right.... thanks berkeman... :smile:
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