PWM motor control immediate help needed

Discussion in 'Homework Help' started by kamalmazhar, Aug 14, 2008.

  1. kamalmazhar

    Thread Starter New Member

    Aug 14, 2008
    2
    0
    I have been assigned the project for bi-directional motor variable speed control using mosfets.I can't use any Ic.Use of H-bridge is compulsory can anyone give me a circuit which i can construct help me please reply soon!!!!

    Note:Use of IC is prohibited.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    We cannot give you a complete circuit, as that is what your assignment is. You would not learn very much if it were just handed to you.

    You have not provided any real specifics about the motor that you are to control. If you have a choice, I suggest that you opt for a low-current, fairly low-voltage (12v or less) DC brushed motor.

    The way to approach any project is to break it down to it's individual functions so that they are easily understood. If something is too complex to understand, it has not been broken down far enough.

    Don't panic, as that will only distract you from your goal.

    [eta]
    No reply yet? You must be out partying instead of studying.

    With such a lack of concern on your part, your project is virtually certain to be a dismal failure.
     
    Last edited: Aug 14, 2008
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    He may simply be from a different time zone and posting before bed. :)

    I would suggest researching discreet PWM topologies. Perhaps a two-transistor astable driving a two-transistor monostable would work. DTL gates could provide steering.
     
  4. kamalmazhar

    Thread Starter New Member

    Aug 14, 2008
    2
    0
    i want to use IRFP 9540 and IRFP 450 for direction control using H-bridge or should i use VQ3001P and Vq3001N.and by using transistors in parallel NPN-BC548C and pNp BC 327.the problem i m facing is input.How to give a signal to generate PWM...???????

    Motor rating 6V and 350mamps or i can also use 12V and 1amp motor...please suggest what should i do...uploading a circuit tell me how would give signal....
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You attached your schematic in .psd format, which is Adobe Photoshop.

    Many people can't read that format on their computers. It's preferred that you use .PNG .BMP or .GIF files; as no special software is needed to read such files.

    I've converted your file to .PNG format and attached it.
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The N-channel Mosfets do not have a pullup resistor on their gates to turn them on when the attached transistor turns off.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You need to build a PWM circuit.
    To start off, look for a transistorized version of a flip-flop, or a square wave oscillator. Then think of ways that you could change the circuit to vary the amount of time that it is ON vs the time that it is OFF.

    We cannot simply hand you a circuit. This requires effort on your part.

    If you don't know where to look, here is one tutorial on a transistorized version of a flip-flop:
    http://www.talkingelectronics.com/FreeProjects/5-Projects/Page16.html
     
    Last edited: Aug 16, 2008
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