Project PipeRotor

Discussion in '3D Printing' started by DL3VB, May 5, 2021.

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  1. DL3VB

    DL3VB Ham Member QRZ Page

    A project for KJ7OCV ;).

    Since there is apparently no small antenna rotor to buy i create my own.
    I mainly use it for my outdoor activities and field days
    PipeRotor for small antennas, 260mm long, 45mm diameter, weight fully assembled ~1Kg.
    with adapter for 20 and 25mm masts.

    PipeRotor_CAD.JPG PipeRotor_Asm.JPG

    All parts without gearmotor and aluminium pipe printed with AnyCubic 3S.
    The position feedback is realized with a magnetic sensor TLE4905 and small
    magnets 2x3mm in a rotor disk.
    I'm still working on a yaesu G232xx compatible controller with arduino.
     
    Last edited: May 5, 2021
    K0UO, N7DWX and KD2UHD like this.
  2. K1RT

    K1RT Ham Member QRZ Page

    DL3VB - wondering whether you may have posted any project details beyond what you've shown above.

    Looks like an interesting idea, maybe there are az-el possibilities as well for a small antenna.

    I have a couple of gearmotors that might be adaptable for this - by any chance do you know offhand the torque and speed in rpm of the gearmotor that you are using?
     
  3. DL3VB

    DL3VB Ham Member QRZ Page

    @K1RT
    The drive is a planetary gearmotor type E192-12-625 from https://www.micromotors.eu.
    GearRatio 625:1 = 6U/min at full speed with 300 Ncm tourqe. (New for ~70€)
    With the centered load on the axle, the torque is easily sufficient.

    Since 6 u/min ist very fast, I've tested two ways of motor control to reduce ratation speed,
    pwm 12VDC and 5 to 12V staged direct voltage. Both versions works well.

    What you can't see in my first post are two angular contact ball bearings. One for keeping the
    axial forces away from the gearbox and in combination the overturning moment
    I am currently thinking about the EL possibility, maybe this can be solved with a linear drive
    and tilt joint, but I don't have a solution for that yet. Needs some brainstorming :)
     
  4. K1RT

    K1RT Ham Member QRZ Page

    Interesting, thanks...

    For position sensing, is the sensor located to the side of the mast? Is there an absolute limit switch (electronic, soft limit) to set the initial position to a known state, or some other method for handling that? I'm guessing that your controller will keep the last position in non-volatile memory - and that the combination of the small size of the antenna along with the holding torque from the reduction gear, rotation with the power off would likely not be a concern, even without using a brake of some sort.

    (One of my gearmotors does have a brake, though - I haven't played with it yet (I picked it up at a ham radio flea market a few years ago and it has been sitting in a drawer since then), so I'm only guessing that it needs a voltage to release a spring-loaded brake, rather than requiring power to hold the brake in place.

    I know that there are a number of different techniques that may be used for absolute positioning, but that gets difficult with only a single sensor.

    I was toying with the idea of using a chain-and-sprocket drive for elevation, but have not really given that any serious thought yet.
     
  5. DL3VB

    DL3VB Ham Member QRZ Page

    The position sensing part is mounted at the backside of the gearmotor on the motor shaft, made with 4
    (optional 8) small magents in a disc. The TLE4905 magnetic sensor counts the full motor revolutions.
    This gives me a resolution of ~13,7888 pulses / degree.

    The TLE4905 ist usefull becaus the power supply range is up to 30V DC. So i can use 12 or 13 VDC with
    a 5.1v zener diode in the arduino signal path. I tried arduino 5v but then the signals are not clean due to
    the voltage drop of the 25m control cable.

    And yes, in my setup a break is not needed because of the 624:1 gear ratio self locking properties.
    To keep the wiring simple (5 wires) there are no hard limit switches, all limits are software based.

    After building up mast and antenna, you rotate the antenna manualy to north (0°) and push a set button.
    this inits the controller position variables to start positons. Currently the rotation range ist absolute 0 to 450° (360° +-45°)
    Since the software is not quite finished yet, there will probably still be a few changes.
     

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