Hub motor controller

Discussion in 'The Projects Forum' started by pjreijiri, Apr 7, 2016.

  1. pjreijiri

    Thread Starter Member

    Aug 19, 2015
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    Hello everyone I am building a robot and I am using hub motors to drive it.
    I attached a picture of the control circuit. I was wondering if you can take a look at it and let me know if it works and if it is possible to have the motor run in reverse or should I create another circuit that has the poles flipped and connected to the motor.

    Regards,
    Patrick
     
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  2. Sensacell

    Well-Known Member

    Jun 19, 2012
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    Your driver is only capable of driving the motor in one direction.

    You need an H-Bridge to make it reversible.
     
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  3. pjreijiri

    Thread Starter Member

    Aug 19, 2015
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    would it be able to handle 48V?
     
  4. pjreijiri

    Thread Starter Member

    Aug 19, 2015
    60
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    PS: it has to handle 8A
     
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Sure one can make an hbridge that supports 48V and 8A..
     
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  6. pjreijiri

    Thread Starter Member

    Aug 19, 2015
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    Hello guys, I have been looking for H-bridges and either they are very expensive modules or can support up to 5A.
    So I decided to make a simplified version.
    What do you think of this circuit. I used IRFP4468 MOSFETs with a 220ohm resistor bank connected to the PIC microcontroller.
    I used 4 MOSFETs for each motor and I "turn on" 2 at a time to drive it forward or reverse. Also for the second motor I flipped the motor connector.

    What do you think?
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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  8. pjreijiri

    Thread Starter Member

    Aug 19, 2015
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    why do i need a whole circuit since the IRFP4468 can be run with a voltage of 2-4V? I am using a pic16 so the 3.3 volts should work
    Am I wrong?
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Most unlikely. Vgs(th) for that FET is specified as min 2V, max 4V. That means in the worst case scenario you may need Vgs=4V to make the FET just begin to turn on and pass a measly 250uA :(.
     
  10. pjreijiri

    Thread Starter Member

    Aug 19, 2015
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    I need to be controlling the motors with a PWM so I can control the speed.
    I tried using the MIC4451 to run the MOSFETs. Both MIC are connected to the PWM of the microcontroller and they will be on the whole time. However I will use npn junctions that are connected to the microntroller and they in turn will control which way the motor is turning.
    Would that work?
    Would connecting a transistor to the VDD of the MIC instead of the MOSFETs be a better idea?
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Not with the motor connections shown. What are the diodes for? The lower ones seem the wrong way round.
     
  12. pjreijiri

    Thread Starter Member

    Aug 19, 2015
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    Alec_t you are right, my mistake.
    I fixed it, took two diodes out and uploaded the new schematics.
     
  13. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Can't see the detail in that pic :(.
     
  14. pjreijiri

    Thread Starter Member

    Aug 19, 2015
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    I am uploading it again
     
  15. pjreijiri

    Thread Starter Member

    Aug 19, 2015
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  16. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Your circuit can't switch the upper FETs on. If you want to drive the motor with 48V then it needs ~58V on the upper FET gates to turn them on. That calls for a high-side FET driver IC such as the IR2110 which Max pointed out in post #7. The MIC4451 used in your circuit is a low-side driver only.
     
  17. pjreijiri

    Thread Starter Member

    Aug 19, 2015
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    But would I be able to drive the IR2110 with a PWM from the PIC16? Because I want to set the speed of the motor
     
  18. MaxHeadRoom

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    Jul 18, 2013
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    Last edited: Apr 15, 2016
  19. pjreijiri

    Thread Starter Member

    Aug 19, 2015
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  20. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    What is? An IR2210 is £1.57 from Mouser, £1.84 from Digikey.
     
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