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driving brushless DC motor

Discussion in 'Electronic Design' started by Michael, Apr 8, 2013.

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  1. Michael

    Michael Guest

    Has anybody dealt with Namiki micromotors (SBL04-08)?
    How to drive them?
    I am playing with Microchip MTD6505 eval kit and it does not seem to like the motor.
  2. I know neither. Does the MTD6505 output enough current to drive the
    (~50mA with not load and more with a load.)

    George H.
  3. passerby

    passerby Guest

    responding to
    Something like this should work for driving *micro* BLDCs:

    But, yes, it's rather intriguing - what do you mean by "does not seem to
    like"? Something like twitching back and forth or simply nothing is happening?

  4. Michael

    Michael Guest

    Sorry, I failed to "Define "does not seem to like".
    MTD6505 eval kit ($60; has very nice GUI with bunch of interesting options) comes with small fan motor.
    I can control the kit motor (start/stop, vary speed), speed is stable, it is proportional to duty cycle setting the GUI shows motor slowing down when I load it (finger).
    When I connect motor I need to use (Namiki), the story is very different.
    It may start only after bunch of unsuccessful attempts (not very good for servo motor; one cannot see any movement because of very high gear down ratio); the speed does not seem to depend on duty cycle (weird!); the speed reading is not stable.
    I did set motor constant according to the motor spec. There is no appreciable starting torque (the motor is geared down at 79:1, I painted the shaft to see it turning).
  5. hamilton

    hamilton Guest

    So what is you're conclusion ?
  6. Michael

    Michael Guest

    I call it servo motor because of the way it is used, not what it is designed for (I do not know what it is, BTW).
    Our ME group specified this micromotor with gear box (4mm in diameter, 16mm long whole assembly), it will be coupled with the target (filter wheel) after another 1:5 gearing.
    I am told (by ME designer) that the target stops instantly after power is disconnested (no inertia to worry about). Similar system (with larger motor, lower torque, lower cost) has been manufactured for years.
    As motor controller generates 1 pulse/turn, the target position is defined with better than 1 degree accuracy - more than enough for the application.
    In other words it looks like perfect servo motor, provided it starts right away when voltage is applied (as opposed to after, say, 30 seconds worth of stuttering)
  7. Fred Abse

    Fred Abse Guest

    My definition, too.
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