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Revision 30 as of 2015-12-31 10:50:54
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Revision 31 as of 2016-01-07 11:33:20
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 * Winter has come and rotator still functional even there has been few -25c temperatures  * Winter has come and rotator still functional even there has been few -20c temperatures
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 * 2 days -30c and still working.. bit surprising.
hacker

wilho

PiRotator

RaspberryPi controlled antenna rotator

Summary:

Current commercial az/el antenna rotators are really expensive(easily over 1500€ with controllers), and moreover technically most are from 90s (analog potentiometer sensors/control, no network, rs/lpt controllable, no web, no rest api, etc).

I tried to take little bit different approach..

Goals:

  • Cheap common hardware (wormgears, nema steppers, rasberrypi, etc)
  • Intelligence on mast (controlbox includes rasberrypi, this enables many things, like SDR on mast)
  • All digital (digital rotary sensors, steppers, tcp/ip, etc)
  • network (only IO is network, controlling thru different apis(REST, legacy RS emulation api))
  • backward compatibility to legacy software, via software RS (ham radio deluxe, pstrotator, etc)
  • project is only for fun, and learning new stuff!

Project status:

  • hardware & software are in quite good shape

  • Rotator is in test use with 2 x 9el 2M yagis
  • Rotator has survied it first storm, with no damage!
  • Winter has come and rotator still functional even there has been few -20c temperatures
  • Worked over 70 EME contacts on first few weeks after getting amp for 2M.. whole setup seems to work good.
  • 2 days -30c and still working.. bit surprising.

Hardware:

  • Steppers:
    • Common 4-lead NEMA 23
    • one full step 1.8 degrees
    • cheap (from 10$/each)
    • easy to control
  • Worm gears:
    • 90 degree Gearbox ?WormGear Speed Reducer 1:60 ratio

    • most important is ?WormGear, because of that we do not need any brake system!

    • relatively sheap (about 50$ / each)
    • with 1:60 reduction we do not need that much power and precision is 1.8 (from step) / 60 -> 0.03angle /step

  • Absolute rotary encoders:
    • Cheapest used 10bit absolute rotary sensors what i could find (KOYO TRD-3A1024)
    • precision is more than enough (10bit -> 1024 -> 360/1024= 0.35 degrees)

    • price about 15€/each
    • 10bit means in this case that there are 10pin for data + 2 power pins
  • IMU sensors for calibration :
    • BerryIMU + MPU9250 IMU chips
    • External weather shielded box which is connected directly to antenna support boom, gives you quite good compass / tilt bearings when calibrated correctly.
    • quite cheap(25€/each) and easy to use (i2c bus, RTIMULib2)
  • Slip rings:
    • https://en.wikipedia.org/wiki/Slip_ring

    • Capsule slip ring OD22MM 18Wires
    • stepper control cables and rotary sensors data cables to upper module go thru axle, with slip ring we dont have to worry about these cables and rotation.
    • about 15€
  • Stepper control:
  • Controller:
    • Raspberrypi 2 or B+
    • full OS
    • enough gpio ports for encoders and stepper control
    • network port
    • could run as "SDR streamer" with rtl_tcp or similar
    • full python
  • Connectors/box/cables/gears/belts/bolts/etc:

Software:

Plan / specs for pirotator server:

  • REST api for controlling (done)
    • you could control your rotator via simple http posts
    • enables many kind of solutions
  • Legacy rotator emulation for legacy software via virtual RS (done)
    • emulates yeasu GS-232B protocol (only control and feedback commands implemented)
    • client OS sees ?SerialPort via virtual serial port software (eg. hw-groups HW virtual serial port -HW VSP3)

    • Tested with HRD rotator and PSTrotator
  • Simpple CLI UI (70%)
    • mainly for debugging purposes
  • Multithreaded structure, and locks/aborts (90%)
    • could use all of those apis/interfaces at same time
  • Neat WEB/JavaScript UI top of REST api (15%)
    • Graphical javascipt / angular UI

Videos

https://www.youtube.com/embed/0F_P8_iJNqI

Pictures

attachment:imu.jpg attachment:pirotator.jpg attachment:outdoor_tests.jpg attachment:controlbox3.jpg attachment:pirotator1.jpg attachment:pirotator2.jpg attachment:slip_ring_encoder_gear.jpg attachment:controlbox.jpg attachment:controlbox2.jpg

description
Current commercial az/el antenna rotators are really expensive(easily over 1500€ with controllers), and moreover technically most are from 90s (analog potentiometer sensors/control, no network, rs/lpt controllable, no web, no rest api, etc).I tried to take little bit different approach..
started
2015-10-02


CategoryProjekti