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Continuous rotation to two gimbals simultaneous - non standard application for gimbals
  • bash
    Hi,
    I'm a newby to this technology, and trying to achieve something not very standard.

    I have two hollow axis gimbals (crazy motor 6008, 20 Ohm, 20magnets, 18 coils)
    Basecam BGC 32bit (v2.56b7), lab power supply
    (and a Servo Tester Gear Test CCPM Consistency Master)

    My goal is to have those two gimbals simultaneous rotate a low rpm (0-10rpm). Ideally the RPM can be set in the SW, or via e.g. an input / service button. (so I don't need any IMU input)
    Application: it should continuous rotate a ferris wheel in a maquette, motor choice was mainly given due to the hollow axis requirements to feed power/data to the wheel. Both motors should work together for more torque. (both sides of the wheel)

    I can get the basic connection going, and have the motor's more or less rotate on the IMU. (not very stable yet though)
    Any tips how to achieve my goals?
    Some questions I run into:
    -if I don't connect any IMU I get ton's of I2C errors. Any way to use the board without IMU?
    -If under 'advanced' I set both Roll and Pitch output to Pitch, only 1 motor reacts. Any way to duplicate two outputs? (Expect I should not just connect two motors to 1 output, but is that correct?)
    -How to get continuous rotation on the motors from OR internal source, OR using an external source (e.g. the servo tester)

    Thanks a lot to get me on my way!
  • LPR
    You should be able to control the speed of two brushless motor by using a single ESC if you can find an ESC that will go very slowly.

    I found this answer by seaching Google for two brushless motors on one shaft with one ESC.

    "If you are connecting them to the same ESC, the roration alignment will be critical, so that the stators and bells are in exactly the same orientation. You are likely to lose some efficiency because alignment is hard.
    In addition, one ESC, you probably have to mount them bell-stator-bell-stator if you try to line up the bells. Mounting one bell reversed might mean that the magnets should not be lined up with each other, but offset. I don't know, but it seems like something to think about."

    My brother built on of these ferris wheels also and his do turn slowly but sometimes he has to start them by hand. He did not use brushless motors.
    Good luck

    Larry
  • bash
    Hi Larry,

    Thanks a lot for your feedback. I've got an ESC-30A (5.5-12.6V BEC 5V/2A), but connecting this to my gimbal seems like a mismatch when looking to expected power/cable dimensions (and I've found multiple places where they say an Servo tester + ESC + gimbal will not result in proper low RPM; ESC is intended for high RPM BLDC motors). I might be wrong here, as mentioned I'm new to all this..
    (==just tested it to give it a go: 12V, 2A PSU to ESC, the control wires to the CCPM servo tester, the output wires to the Gimbal, get some PWM sounds and vibration, but no rotation==)
    (and regarding bell-stator-bell-stator order; think that bell-stator-stator-bell, with the 3 cables reversed should give the exact mirrored effect?)

    Anyway, using the alexmos board (dedicated for gimbal motors) to get a least one motor spinning smoothly continuously would be my initial goal.

    Does the SimpleBGC GUI not offer an option to spin a motor continuously in an easy way, without any IMU connected? That seems such a simple option for an advanced controller. But sometimes the simple things can be hard to achieve I guess?

    Thanks all for any thoughts / suggestions to get 1 (or preferably 2) gimbal motors to simply turn at a continuous speed.
    Bas
  • bash
    ...anyone else with helpfull insights if this is possible / how to get this to work?
    Thanks!
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