dc motor control... Help.

Discussion in 'The Projects Forum' started by rrrchandu, Sep 18, 2011.

  1. rrrchandu

    Thread Starter New Member

    Aug 9, 2010
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    how do i control a dc motor using mosfet as a switch..? what should be the basic supply for switching the mosfet? otherwise i'd really appreciate if you give your own idea about my project.. thank you
     
  2. iONic

    AAC Fanatic!

    Nov 16, 2007
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    I can suggest reading about the LM555 IC and PWM(Pulse Width Modulation) as this can vary the motor speed with pulses to the MOSFET, but without an explanation of your project and it's specifications there is little else to offer you.
     
  3. jwilk13

    Member

    Jun 15, 2011
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    There has been a lot of discussion on this subject here on these forums. For example, take a look here to start. This will help you simply control the speed of the motor.

    If you're wanting to reverse the direction of the motor, you'll want to do some research on the H-Bridge.
     
  4. rrrchandu

    Thread Starter New Member

    Aug 9, 2010
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    Thanks for the reply...,

    But, could you please explain or send a link to make me know what the specialty of h-bridge as the same type of control is possible with two MOSFETs only...:confused:
     
  5. jwilk13

    Member

    Jun 15, 2011
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    I've never seen an H-bridge with only two MOSFETs, but I haven't encountered them often. The ones I'm familiar with use four MOSFETs to control the direction of the motor.

    If you provide us with some more details on your project, we can probably give better feedback.
     
  6. rrrchandu

    Thread Starter New Member

    Aug 9, 2010
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  7. SgtWookie

    Expert

    Jul 17, 2007
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    Yes, but it requires a dual rail supply. That's kind of wasteful if you can accomplish it using an H-bridge instead of a half-H.
     
  8. rrrchandu

    Thread Starter New Member

    Aug 9, 2010
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    Thank you....,
    And I have another problem, that to attach a free wheeling diode in the h-bridge. Is it equal to connect diodes across MOSFETs, rather than across motor.....?? , :confused:
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    With an H-bridge, you can't connect standard diodes across the motor because they would short across the motor in one direction.

    You can connect diodes across each MOSFET instead. Use diodes with a low recovery time (Trr). Don't use standard rectifier diodes like 1N400x or 1N540x; they just are not fast enough.
     
  10. rrrchandu

    Thread Starter New Member

    Aug 9, 2010
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    Thank you...
     
  11. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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