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Mosfet H bridge driver only gives out 3-4V under load. Why??

Discussion in 'Motor actuators and drivers' started by HAVOG, Jan 20, 2009.

  1. HAVOG

    HAVOG New Member

    Joined:
    Jan 2, 2009
    Messages:
    34
    Occupation:
    High and Low voltage technician, production automa
    Location:
    Denmark
    Balance:
    299Coins
    Ratings:
    +0 / 0 / -0
    Hi..

    My H-bridge DC motor driver is acting wierd. When under load, the voltage on the motors is only 3-4V and they have no torque. I can easily hold them back.

    When I remove the wires from the motors and activate the sliders in profiler i meassure + - 13V.

    And when I first start it up it takes a couple of minutes of activating before the motors respond to anything. Like they need to warm up or something.

    I soldered in 8 new mosfets an 4 new BC546b.


    I'm out of clues.. pls hlp..

    Henrik
    HAVOG, Jan 20, 2009
    #1
  2. Michael N.

    Michael N. Member

    Joined:
    Dec 27, 2007
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    Germany, NRW, Düren
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    611Coins
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    Hi,
    in both directions?. Sure that the Mosfets (IRFZ44) are 100% OK?. Those get broken faster than the IRF4905, thats my experience.
    If the motor turns in one direction, are they (IRFZ44) going very fast hot?.
    Michael N., Jan 22, 2009
    #2
  3. HAVOG

    HAVOG New Member

    Joined:
    Jan 2, 2009
    Messages:
    34
    Occupation:
    High and Low voltage technician, production automa
    Location:
    Denmark
    Balance:
    299Coins
    Ratings:
    +0 / 0 / -0
    Hi

    I just put in 8 new mosfets. I now tested the H-bridge on Thanos's instruction and the H-bridge seems to be okay. So maybe it's my AVR/PWM controller that doesn't give the right signal to the BC546's - wich provide the opening voltage for the mosfets..

    I'll do some more testing and return w. answer..


    H. Vogt
    HAVOG, Jan 22, 2009
    #3