Power supply question for DHB-10 motor controller

Hello,
I have been trying to wrap my head around the following. And, it might be a little over my head. A few months ago I bought a DHB-10 motor controller (#28231) and (2) 6-15V gear motors with encoder (#28819). I am trying to better understand what I need in order to power the motors and controller. Looking at the motor, the label says “DC/6V”. Looking at the data sheet it says “6-15V”. I assume that means that it is a 6V motor, but can be powered up to 15V. I am also a little puzzled at what current is required to drive the motors. The data sheet says “3.5A @6V (>5A @ 12V)”. Where should I aim? Is it something like 6V -> 3.5A x 2 motors = 7A power supply? Or, 12V -> 5A x 2 motors = 10A power supply? Do you factor a slightly higher amperage as a safety factor? I am concluding that the motor draws more current at higher voltages (if my terminology is correct).
I am thinking of testing this all on a table top so would be looking to plug something into a standard wall outlet (110V).

Part 2 of this question:
If I understand the data sheet on the motor controller, it receives it’s power from the same 6-24V that drive the motors. If I connect the motor controller to a Parallax Activity Board, the PAB will also need some sort of power. Is it possible to drive both boards with the same power supply? I assume this might increase the required amperage of the ‘system’. This relates to my safety factor question above.

Although I have been playing with the Propeller for around 8 years now, a standard ‘wall wart’ has been good enough. I am assuming connecting the motor controller and motors will require some more muscle.

I am looking to learn what others have used for their setups? Any help and suggestions would be appreciated. Thank you.
-Rob

Comments

  • 7 Comments sorted by Date Added Votes
  • RobertW wrote:
    The data sheet says “3.5A @6V (>5A @ 12V)”. Where should I aim? Is it something like 6V -> 3.5A x 2 motors = 7A power supply? Or, 12V -> 5A x 2 motors = 10A power supply? Do you factor a slightly higher amperage as a safety factor?

    Yes to all three questions. I'd go 150% on the current. That motor controller does not operate in current-sourcing/sensing mode. So the voltage you provide is the voltage the motors will see.
    If I connect the motor controller to a Parallax Activity Board, the PAB will also need some sort of power. Is it possible to drive both boards with the same power supply?

    Theoretically, yes, as long as the PS voltage does not exceed the AB's input specs. But I would use a separate PS for the Activity Board, or else a DC-DC converter from the motor supply like the Arlo Power Distribution Board uses.

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    I'm going to guess that the motor doesn't say it draws 3.5A without the words "stall current", which is the maximum current the motor can draw. Usually motors will also list a no-load current which is much less. There is no way to know the loaded current draw without testing as it will vary based on the specifications and weight of your robot.

    The DHB-10 cannot provide power to the host controller. You would have to power the host controller separately. If you're looking for a wall adapter our 12V @ 2A supply (#750-00003) should work for testing. You could make a Y-Adapter to provide power to the Activity Board via the 2.1 mm barrel connector as well as to the DHB-10 via stripped wires.
    Chris Savage | Engineering Tech | Main Office: (916) 624-8333 | Direct to Tech Support: (888) 997-8267 | Website | Twitter | Google+
  • Thanks guys. I could keep the power supplies separate and just plug the activity board into the wall with my current power supply, I was just looking to reduce the need for 2 power supplies.

    Yes Chris, you are right, the amps I listed were at the stall current. I was not sure if this was the number to base a supply on. I am assuming that a lower power supply current would result in the motor stalling at a lower torque?

    Question #3 that I forgot to ask earlier: Do I need to change the fuse in the DHB-10 board to relate to the power supply and motors I am using?

    I will look at the Parallax power supply you mentioned, and the Arlo Power Distribution Board.

    Thank you for your comments.
    -Rob
  • I second Chris Savage's idea of making a Y-adapter to power both boards from the same power supply.

    You could use a different fuse if you want to. The main reason one would use a different fuse if to protect the motors. You could replace the 20A fuse with a 2A or 3A fuse if you were concerned about the motor stalling. Since these motors include encoders, you could monitor the encoder feedback to make sure the motors were moving as expected. If the motors weren't moving when expected, the program could quickly cut power to the motor(s) to prevent damage.

    I've had trouble powering motors from wall-warts in the past. It's been my experience DC motors often perform better when powered from batteries. I assume this has something to do with the inductive nature of the load.

    Depending on what you're trying to accomplish the your programming ability, it may be possible to do without the Activity Board. The DHB-10 can be programmed to control the motors without input from another controller.

    It's certainly possible to control motors with only the DHB-10, an USB to serial device and a terminal program such as Parallax Serial Terminal.exe.

  • If you run both from the same power supply, run separate cables from each back to the PS. DO NOT daisy-chain the power connections!

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    RobertW wrote: »
    Yes Chris, you are right, the amps I listed were at the stall current. I was not sure if this was the number to base a supply on. I am assuming that a lower power supply current would result in the motor stalling at a lower torque?
    Thank you for your comments.
    -Rob

    A power supply is rated at how much current it can supply. If you try to draw more from it than it can supply, you simply won't get it. In some supplies the voltage may drop as excessive current is drawn. But stalling the motor is a worst case scenario. In a robot it is more of a possibility, but you're typically running on batteries. In another system that might be a fault condition and you may even fuse for current draw past what you're expecting to use. For example, if your application draws 1A during load/run, you might put a 1.5A slow-blow fuse so that if the motor stalls (trying to draw 3.5A, perhaps) that the fuse blows.
    Chris Savage | Engineering Tech | Main Office: (916) 624-8333 | Direct to Tech Support: (888) 997-8267 | Website | Twitter | Google+
  • Hi guys,
    Thank you for the replies. I think I now have a better understanding on how to move forward. Thank you again for your comments and suggestions.
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