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Original question:

DRV8308: I can not find file: Filter calculator.xls

DRV8308: the motor cannot spin in close loop mode

user5831319
Intellectual 260 points
Part Number: DRV8308

hi,

i bought one piece of the drv8308evm board，and I encountered several problems during the test。

1 When the speed is relatively low, for example, the output frequency of MSP430 is 20Hz, the rotation of the motor is very rough, and even a step by step rotation can be clearly felt.

2 when i first test it, i changed some register value,but i forgot record the initial value，do you have the value numbers?The evm board can no longer close the loop at a lower speed. I tried to adjust a lot of register values, but I can’t find the original state.

3 My purpose is to drive the motor in a closed loop within the range of 200~6000rpm（2  or 4 pole pairs）. If possible, can you give me some suggestions on how to adjust it.

Thank you

  • 0
    Intellectual 260 points

    test video is as below,extern clock frequency is 40 hz.

    register setting is as below

    clkin and fg waveform is as below 

  • 0 in reply to user5831319
    TI__Guru 65330 points

    Hello,

    Thanks for posting on the MD forum!

    If you power off the EVM, remove the USB connection, restart the software, and reconnect everything again, the default settings will be loaded. Please try this first.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Intellectual 260 points

    Adam,

    Thanks for your reply.I will try it tomorrow morning because it is mid-night now in my country.

    I want to know whether the chip can start and drive a motor smoothly at a low speed such as 100 rpm？

    And if you have seen the video and the picture,could you tell me why this happened?What should i do to avoid this?

    Thanks a lot.

  • 0 in reply to Adam Sidelsky
    Intellectual 260 points

    Adam,

    i have tested the evm board with the motor in the evm case after fullly reset the board.i found that the motor spun roughly at clock frequency lower than 50Hz that generated by the msp430,even though i changed some register value,just as my video uploaded yesterday.And the motor couldnot turn to close-loop mode.i also found the maximum speed of the motor with the evm board was about 175Hz,ang the minimum speed was about 50Hz.

    now i want to drive the motor at a speed of 200rpm,what should i do?

    16:40

    I tried to change some register value this afternoon.in some conditions the motor can spin,but not smoothly.I have a question,if we want to change the motor speed,wo also need to change the registers at the same time?

  • 0 in reply to user5831319
    Intellectual 260 points

    is there someone else see the question?could you help me solve it?

  • 0 in reply to user5831319
    TI__Guru 65330 points

    Hello,

    The default values for the GUI and EVM should work correctly for the motor provided in the kit.

    Did you try the tuning steps as listed in the User's Guide?

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Intellectual 260 points

    Adam,

    Thanks for replying me.

    I tried the default value.these setting could make the motor spin at a higher speed than 50Hz.But when i tuned the speed down lower,the motor works not good,such as the motor spin step by step,and some times the power supply seems to be disturbed.After i changed the reg values as it says in the manual,he motor could spin smoothly at a speed of 40Hz,but I still cannot find the corrext value to make the motor spin at a lower speed.My desired speed is 200rpm.

    If you have any suggestion,plesae tell me.

    Thanks .

  • 0 in reply to user5831319
    TI__Guru 65330 points

    There is a lower limit to the MSP430 PWM generation, also with low pole count it is very difficult to spin at low RPM.

    Can you try a different motor with higher pole count?

    Regards,

    -Adam