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Controller for 6V BLDC for "zero speed" operation?

dnilsson
Prodigy 180 points
Other Parts Discussed in Thread: DRV8308, DRV8307, DRV8303, DRV8835, DRV8837, DRV8844, DRV8839

Hi,

I have a request from a customer to develop a motor controller for a BLDC motor and I'm currently searching for a suitable solution. The motor is a Maxon 455020, (http://www.maxonmotor.com/medias/sys_master/root/8813537460254/14-170-EN.pdf) which is a 6V BLDC motor with 3 hall sensors. The tricky bit here is that the customer needs to be able to control the motor down to "zero speed", that is I need to be able to support just moving a third of a turn at a time or spinning 1245.3 turns for example. So more or less like a stepper motor, but with a lot less steps per revolution of course. Given that we need to operate down to "zero speed" I guess using the hall sensors is mandatory since a sensor-less approach as far as I understand will not work? I'm looking for a suggestion for a controller that will allow controlling this motor in the requested fashion. DRV8308 or DRV8307 seems to be the closest I've found so far, the 6V motor voltage isn't directly supported but I'm assuming driving the motor at let's say 10V should be OK as long as I setup the current limiting feature of the driver to match the motor rated current? Is there a better match? I'd rather use an existing controller compared to doing it all in software from scratch, but an existing MCU SW solution that can be adapted is OK as well.

Thanks!

  • 0
    TI__Guru** 114905 points
    Hi Dnilsson,

    Can you provide a little more information?

    What is the full voltage range of the system?
    When moving 1/3 turn, is it necessary to hold at that position?
    Any additional information that you can share will help us recommend the proper device.

    Many of our controllers are designed to either spin or remain at zero. Trying to use one in a stepper like fashion may require a mcu and individual control of the outputs. Examples of this include the DRV8303 or DRV32xx devices.
  • 0 in reply to Rick Duncan
    Prodigy 180 points

    Hi Rick

    Certainly, as far as I know I'm free to design a suitable power supply as well so "whatever voltages needed" I guess we can assume are available.

    The motor will be connected to a gearbox, I find it hard to believe that a large amount of holding torque would be required as a result. As long as I can stop the motor precisely that should be enough.

    My plan is to drive the controller from a MCU, so we can assume one is available.

    Regards

    Daniel

  • 0 in reply to dnilsson
    TI__Guru** 114905 points
    Hi Daniel,

    There is not anything that is specifically designed for this application, but there may be a few options available. As you pointed out, raising the voltage will allow devices such as the DRV8303 and others to work. Doing so generally requires adding current regulation.

    Another possible option is using one of the DC motor drivers at the nominal 6V. Assuming the motor is not damaged there motor should run without requiring current regulation. It is generally a good idea to add it though. Devices such as the DRV8844 (min voltage 8V) could be used, or (3) DRV8837 or (2) DRV8835 or (2) DRV8839.

    Please take a look at the DRV8839 first. There is one extra half bridge that is unused, but from a cost and possibly footprint point of view this may be the best option.

    Also, please note this configuration has not been tested to my knowledge. Conceptually it should work.
  • 0 in reply to Rick Duncan
    Prodigy 180 points
    Thanks Rick, I'll consider these solutions. My conclusion is that I need a custom MCU based "controller" to be able to solve this task.