PWM motor control

Discussion in 'General Electronics Chat' started by Tobias, Mar 4, 2010.

  1. Tobias

    Thread Starter Active Member

    May 19, 2008
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    I am wanting to control a 24v motors speed. I am using a PIC 16F886 with a P type MOSFET. Using the CCP1 output to control the MOSFET with HPWM. What is a good frequency to use? Any suggested MOSFET part numbers?

    Thanks
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Why a P-ch MOSFET?

    It would be easier to use an N-ch MOSFET; that way you can switch the low side of the load. Besides, N-ch MOSFETs have better specs than their complementary P-ch versions.

    If you are wanting to go higher than a few hundred Hz, you're going to need a gate driver IC.

    What is the motor's current at stall?
     
  3. Tobias

    Thread Starter Active Member

    May 19, 2008
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    What would you suggest based on the attached document? What are the benefits of higher than 200 hz?

    Thanks
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    If you have the PWM above 25kHz, it will be beyond audio range, so you won't hear it. However, it takes a fairly capable gate driver to turn a MOSFET on and off quickly at those speeds.

    At low PWM speeds, you'll have more losses in the motor, and you'll hear the motor "sing". However, you can get by without a gate driver.

    I don't see stall current listed. Highest current shown is 7.14A near the bottom. Stall current will be several times that.
     
  5. Tobias

    Thread Starter Active Member

    May 19, 2008
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    Thanks, I will look around for a N-Type MOSFET IC Driver schematic. Any suggestions on MOSFET and drivers?
     
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