I just smoke two h bridge motor driver

Discussion in 'General Electronics Chat' started by bug13, Jan 28, 2014.

  1. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
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    Hi guys

    I just smoked two motor driver like these:

    http://www.ebay.com/itm/0-36V-Rated...693?pt=LH_DefaultDomain_0&hash=item2ecdfe19fd

    here is the contril pins:
    • Forward: DIR = 1 PWM = PWM
    • Reverse: DIR = 0 PWM = PWM
    • Brake: DIR = X PWM = 0

    The motor run about 1-2 seconds, a "pop" sound is heard, then gone. No physical damage can be seen by eyes. No mosfet is warm/hot, they are all still at room temperature.

    it looks like on normal PWM mode, the motor is switched between on and brake, is there a reason for this?

    Because I think that might be the reason why my motor controller is smoked.

    My DC motor is 250W, 24V, no load current is about 2A, rated current is about 15A. Power by two 12V sla batteries.
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,383
    495
    Is there a fuse?
     
  3. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
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    one 32A fuse

    first controller, fuse is gone, a least one mosfet is gone (D and S shorted) but no visual damage, not warm/hot

    second controller, fuse is not brown, at least one mosfet is gone (D and S shorted), again no visual damage, not warm/hot
     
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,772
    931
    Braking the motor usually involves shorting the windings. The motor then becomes a generator. I suspect it is producing very short high voltage spike that is taking out your mosfets. I would have thought a PWM circuit would switch between on and off - not on then 'shorted windings' then on again.

    Or it could just be the mosfets are rated in chinese volts and not real volts. Or it could be something else. A scope might show you the presence of spikes but you would have to be fast and it would entail the 'smoking' of another driver board.

    not any easy way to troubleshoot this one without some more fets dying. Go back to the start and see if there is a way to get the driver board to just switch off and on without using a brake function.
     
  5. Metalmann

    Active Member

    Dec 8, 2012
    700
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    To me, this part doesn't sound correct:


    "Able to withstand high current overload, the maximum current up to 110A."

     
  6. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Hmmm. I don't see any clamp diodes on that board.
     
  7. vrainom

    Member

    Sep 8, 2011
    109
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    Well, if it's like I imagine instead of a flywheel diode they're using a flywheel mosfet, it's more efficient.
     
  8. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Could be, but usually there is still a small diode to avoid shoot thru.
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Put some good diodes. The internal one is not enough
     
  10. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    No there isn't, I am going to add some see what happen.
     
  11. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    And one more question:

    Is there a reason why they design the controller as ON - BRAKE on PWM mode? Instead of ON - OFF on PWM mode?

    here is what the waveform looks like

    [​IMG]
     
  12. BobTPH

    Active Member

    Jun 5, 2013
    782
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    Yes, it takes the place of the diode. When the current is off the windings are shorted stopping any high voltage pulse when turning off.

    Bob
     
  13. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    Is there any other advantage beside saving some diodes? Mechanically speaking, I am thinking it's a disadvantage as it break every duty cycle, it will increase the mechanical stress. Am I right?
     
    Last edited: Jan 29, 2014
  14. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    Also, after replacing the mosfets, I found my board is very warm around the mc34063, and my board was not connected to any motor.

    after a bit of digging, I find that if I set my power supply's current limit to over 1.2A, it work fine, draw only 12mA.

    But if I set my power supply's current limit to say 500mA, it will draw 500mA, up to 1.2A.

    How do I fix this?

    PS: I added a bigger inductor, it seems to work over 900mA. Adding cap on the input of mc34063 don't seem to fix anything. But I have no low ESR cap with me anyway, I just try normal cap.
     
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