• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 32 subscribers
  • Views 2352 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Unexpected DRV5013 output with unknown magnet

scislowski.daniel
Prodigy 125 points
Other Parts Discussed in Thread: DRV8308EVM, DRV5013, DRV8308

Hello,


I try to run bldc motor with drv8308evm board. First I tried to use small motor which is not my target, but I hadn't another in that time. I made PCB with DRV5013 sensors with 120 degrees distance on a circle and I could run this motor. Then I received my target motor and I made similar (only a little bit bigger) PCB with sensors for it. But I can't spin it. I tried investigate what is wrong, and I see the hall sensors output is not what I expected, because all three signal are almost in phase. I found same magnet for the second motor and behaviour is similar with both. Below are pictures from oscilloscope, which present situation with both motors. Could you suggest what to do in this situation?  

PS: I can't start second motor, to capture these signals I rotated magnet by hand.

Fisrt OK, we can see the 'switching' sequence, always at least one signal is '1' :

Sencond BAD, output in phase:

  • 0
    TI__Guru** 114905 points

    Hi Daniel,

    Do the two motors have the same number of poles? This may be the reason for what you are seeing.

    RE previously provided some guidelines for hall sensor placement here ( LINK )

  • 0 in reply to Rick Duncan
    Prodigy 125 points
    Hi Rick,

    you are probably right. The second motor has 24 poles, the first has 20 poles. So I assume I should place sensors at 0, 10 and 20 degrees or e.g. 0, 130 and 260.
    Could you say more about this: "Determining where 0° must sit is more involved. If you measure your TelcoMotion motor you might be able to figure that part out."

    Regards
    Daniel
  • 0 in reply to scislowski.daniel
    TI__Guru** 114905 points
    Hi Daniel,

    RE is not available to comment. I think he was referring to positioning the hall sensors to provide the proper states when the coils are energized.
  • 0 in reply to scislowski.daniel
    TI__Mastermind 20985 points
    In order for the phase drive to align with the back-EMF, the Hall position versis stator winding is important. You can imagine that if the phase winding is energized right when the Hall signal changes, the pole versus winding position must be correct.

    The DRV8308 in that other thread lets you tweak the drive timing versus Hall signal, to tune optimal performancw if the physical Hall placement on the PCB isn't perfect.

    Best regards,
    RE