---
title: "Antenna Rotor - Part 2 | Lets Hack It"
description: "Build a satellite tracking antenna rotor. This guide covers modifying motors, 3D printing parts, and using ESP32 with TMC2209 drivers."
image: "https://lucasteske.dev/assets/posts/tracker-mount-2/assembled-elevation-shaft.jpg"
---

# Antenna Rotor - Part 2

 ![Antenna Rotor - Part 2](/assets/posts/tracker-mount-2/assembled-elevation-shaft.jpg)Written by Lucas Teske   
on 1 April 2021

Continuing the tracker project, I managed to make some significant progress. As Demilson (PY2UEP) had cut the original motors, I did the same. The azimuth motor was too rusted and I eventually destroyed one of the coils (which I wanted to salvage the wire), but in the end the shaft went out.

* * *

After removing the shaft, I broke the magnet with a hammer until there was any piece left. That way, the only thing that would be left there is the shaft and the hexagon magnet support.

![Hexagon Magnet Support 1](/assets/posts/tracker-mount-2/azimuth-motor-shaft.jpg) ![Hexagon Magnet Support 2](/assets/posts/tracker-mount-2/azimuth-motor-shaft2.jpg) ![Hexagon Magnet Support 3](/assets/posts/tracker-mount-2/azimuth-motor-shaft3.jpg)_Motor shaft showing the hexagon support_

For the elevation motor, I made a cut in a circular mark around the exit of the shaft. That way I could use the same support for coupling with the reduction gears.

!["lid" of the elevation motor after cut](/assets/posts/tracker-mount-2/elevation-shaft-support.jpg)_“lid” of the elevation motor after cut_ ![Lid + Reduction Gears](/assets/posts/tracker-mount-2/elevation-shaft-support-with-reduction.jpg)_Lid + Reduction Gears_ ![Motor Pieces](/assets/posts/tracker-mount-2/elevation-motor-parts2.jpg)_Motor Pieces_

For the shaft, it was nescessary to reduce its size and made a bevel so I could fit it better in a 3D Printed part. To do so, I use two plywood pieces to hold the shaft while me and my father cut it. For the bevel, we used a grinder.

![Plywood and cut shaft](/assets/posts/tracker-mount-2/elevation-shaft-cut.jpg)_Plywood and cut shaft_ ![Cut shaft on motor head](/assets/posts/tracker-mount-2/elevation-shaft-support-with-shaft.jpg)_Cut shaft on motor head_

With that, I could then start the 3D Drawings for the adapters.

## 3D Prints

After A LOT of trial and error, I managed to make good fittings between the shafts. But then I realized a problem: The space for the azimuth axis was **extremelly** limited, in the way that my 40 mm NEMA17 motors were too big for it.

![Azimuth Adapter](/assets/posts/tracker-mount-2/try-azimuth-44adapter.jpg) ![Azimuth Adapter](/assets/posts/tracker-mount-2/try-azimuth-44adapter-place.jpg)_Azimuth Adapter_

Then I had to buy some “slim” motors to use in that place. I got a bit concerned with the final torque, but my attempts to make gears and other stuff were all failed. The motors I bought in Aliexpress (see links in the end of this post)

While the motor wasn’t arriving, I started optimizing the adapters to be the shortest as possible, saving all space I could. I use [FreeCAD](https://www.freecadweb.org/) for being free and where I can do faster / better drawings. But don’t assume I’m a 3D Designer, because I’m not. My parts are only “functional”.

![Azimuth Shaft Adapter](/assets/posts/tracker-mount-2/azimuth-shaft-adapter.jpg)_Azimuth Shaft Adapter_ ![Azimuth Support](/assets/posts/tracker-mount-2/azimuth-support.jpg)_Azimuth Support_ ![Elevation Shaft Adapter](/assets/posts/tracker-mount-2/elevation-shaft-adapter.jpg)_Elevation Shaft Adapter_ ![Elevation Adapter](/assets/posts/tracker-mount-2/elevation-motor-adapter.jpg)_Elevation Adapter_ ![Three stepper motors on a workbench with tools and wires nearby.](/assets/posts/tracker-mount-2/exploded-elevation-shaft.jpg)

And the first axis to work was the elevation. To do so I used 40 mm NEMA17 motors (link in end of this post), which came with a closed-loop magnetic encoder driver. But in the end I went to use a TMC2209 to control instead the board that came in because it was easier and quieter.

https://www.youtube.com/embed/cfUtCqb3oxAhttps://www.youtube.com/embed/ENTpTZaiXl4

After the new azimuth motors arrived, I just tried to fit everything. And it did! se ia caber. E coube!

![Azimuth](/assets/posts/tracker-mount-2/assembled-azimuth-support.jpg) ![Azimuth Motor in place](/assets/posts/tracker-mount-2/azimuth-motor-inplace.jpg)

And also working!

https://www.youtube.com/embed/-4U-ofHaF0E

After everything was working, I did some tests to check what was the final resolution and reduction for both axis. To do so, I used the following code with an ESP32 to control the TMC2209 drivers, and for angle measurement I used my phone attached to the elevation base.

```
#include <TMCStepper.h>

#define STEP_PIN 12 // Step
#define EN_PIN 23 // Enable

#define SERIAL_PORT Serial2 // TMC2208/TMC2224 HardwareSerial port
#define DRIVER_ADDRESS 0b00 // TMC2209 Driver address according to MS1 and MS2

#define R_SENSE 0.11f 

TMC2209Stepper driver(&SERIAL_PORT, R_SENSE, DRIVER_ADDRESS);

void setup() {
  pinMode(STEP_PIN, OUTPUT);
  pinMode(EN_PIN, OUTPUT);
  digitalWrite(EN_PIN, LOW);
  
  SERIAL_PORT.begin(115200); // HW UART drivers
  Serial.begin(115200);

  driver.begin(); // UART: Init SW UART (if selected) with default 115200 baudrate
  driver.toff(10); // Enables driver in software
  driver.rms_current(1000); // Set motor RMS current
  driver.microsteps(2); // Set microsteps to 1/16th

  driver.en_spreadCycle(false); // Toggle spreadCycle on TMC2208/2209/2224
  driver.pwm_autoscale(true); // Needed for stealthChop

  Serial.println("OK");
  digitalWrite(EN_PIN, HIGH);
}

bool shaft = false;

void loop() {
// Serial.println("TURN");
  if (Serial.available() > 0) {
    int z = Serial.read();
    if (z == 'a') {
      Serial.println("Stepping 10000");
      digitalWrite(EN_PIN, LOW);
      for (uint32_t i = 10000; i>0; i--) {
        digitalWrite(STEP_PIN, HIGH);
        delayMicroseconds(350);
        digitalWrite(STEP_PIN, LOW);
        delayMicroseconds(350);
      }
      digitalWrite(EN_PIN, HIGH);
    } else if (z == 'b') {
      shaft = !shaft;
      Serial.print("Shaft direction: ");
      Serial.println(shaft);
      driver.shaft(shaft);
    }
  }
}
```

The results were:

- Elevation Axis 
  - Aproximated Reduction: 1:3500
  - Angular Resolution: 0,000117 deg / step
  - Maximum Speed: 0,62 deg / s

- Azimuth Axis 
  - Aproximated Reduction: 1:392
  - Angular Resolution: 0,0046 deg / step
  - Maximum speed: 6,3 deg / s

The results looks promissing and, if everything goes right, will be enough for tracking satellites!

The next step is to code / assemble the required software/hardware to control it through network!

The 3D Models (Both freecad and STL) are available in Thingverse (see links section)

## Links

- [Azimuth Motor](https://s.click.aliexpress.com/e/_AOhCSe)
- [Elevation Motor (Closed-Loop)](https://s.click.aliexpress.com/e/_ADtVZs)
- [Elevation Motor (Normal)](https://s.click.aliexpress.com/e/_9zgziK)
- [TMC2209 Drivers](https://s.click.aliexpress.com/e/_AoG3ZC)
- [STL / Freecad Files](https://www.thingiverse.com/thing:4813288)

## Cite this article

### Suggested citation

Lucas Teske. “Antenna Rotor - Part 2.” _Lets Hack It_, 2021. [https://lucasteske.dev/2021/04/rotor-antenna-parte-2](https://lucasteske.dev/2021/04/rotor-antenna-parte-2).

### BibTeX

```
@misc{teske2021rotorantennaparte2,
  author = {Lucas Teske},
  title = {Antenna Rotor - Part 2},
  year = {2021},
  publisher = {Lets Hack It},
  url = {https://lucasteske.dev/2021/04/rotor-antenna-parte-2}
}
```