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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:

1. Cheap common hardware (wormgears, nema steppers, rasberrypi, etc) 2. Intelligence on mast (controlbox includes rasberrypi, this enables many things, like SDR on mast) 3. All digital (digital rotary sensors, steppers, tcp/ip, etc) 4. network (only IO is network, controlling thru different apis(REST, legacy RS emulation api)) 5. backward compatibility to legacy software, via software RS (ham radio deluxe, pstrotator, etc) 6. project is only for fun, and learning new stuff!

=== 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 on this case that there are 10pin for data + 2 power pins

    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

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