Urgent HIP4081 Issue

Discussion in 'General Electronics Chat' started by gv260ea, Apr 8, 2015.

  1. gv260ea

    Thread Starter New Member

    Apr 8, 2015
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    Hi, Recently i've been developing a motor driver bıard with the HIP4081. I'm applying PWM to the BHI pin and 3.3V to the ALI pin. My mosfets are IRFS7437 and there is a 15ohm resistor between their gates and the driver pins. I do not get the pwm out of the mosfet. The first photo is the output pin under load and the second pin is the gate pin of the mosfet. Notice that there is an offset in the gatepin which the square wave doesn't go to GND. What is causing this issue and how can i solve it. I have also attached the schematic of the board.
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Maybe you could post a schematic of the driver and the FETs all in one diagram.
     
  3. gv260ea

    Thread Starter New Member

    Apr 8, 2015
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    I did its in schematic.pdf
     
  4. gv260ea

    Thread Starter New Member

    Apr 8, 2015
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    Here is the motor driver section [​IMG]
     
  5. ronv

    AAC Fanatic!

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    I don't see any motor or the FETs.
     
  6. gv260ea

    Thread Starter New Member

    Apr 8, 2015
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    [​IMG]
    They are in the black square box. and the motors are attached between M2A and M2B
     
  7. gv260ea

    Thread Starter New Member

    Apr 8, 2015
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    The same thing happens when i attach the motor between M1A and M1B
     
  8. ronv

    AAC Fanatic!

    Nov 12, 2008
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    What is the part number of the opto? It doesn't look like it is pulling to ground. It might be a good idea to run it at a higher voltage (although it looks like you input is 12v not 3.3).
    That schematic is almost impossible for anyone that hasn't lived with it to understand. :D
     
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