Project tutorial
Antenna Rotator controller compatible with tracking software

Antenna Rotator controller compatible with tracking software © GPL3+

Simple controller for homemade (or commercial) antenna rotator. Manual command or USB via computer tracking software: Orbitron, SatPC32 ...

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Components and supplies

Ph a000066 iso (1) ztbmubhmho
Arduino UNO
Arduino Uno board
×1
09939 01
Rotary potentiometer (generic)
max. 1Kohm (500 Ohms work better)
×2
Bourns pec11r 4215f s0024 image 75px
Rotary Encoder with Push-Button
×2
12002 04
Breadboard (generic)
×1
Relay Module (Generic)
2 modules x 2 relay NO-Com-NC
×2
Fairchild semiconductor fqu13n06ltu image 75px
Power MOSFET N-Channel
power mosfet module (min 12V/3A)
×2

Apps and online services

About this project

Latest update June 2021

This project started as an entertainment and became a serious piece of equipment.

The Controller accepts manual positioning of the antenna, by means of two rotary encoders, Azimuth and Elevation. It can automatically track satellites, when connected by USB to a PC running satellite tracking software.

It's compatible with all tracking software using EasyComm2 protocol / 9600 bauds. PstRotator, WXtrack, HRD, MacDoppler... Even WXtoIMG can control the rotator.

It works directly with Orbitron, with a DDE plugin from http://tripsintech.com/orbitron-dde-azimuth-elevation-to-serial/

You can find more information on my site https://racov.ro/index.php/2020/12/09/arduino-based-antenna-rotator-part3-software-tracking-update/

If you have 180deg. elevation system, you're good, give me an email. The controller outputs a response on serial, for the tracking software to display the real antenna position on the screen. So far, only PstRotator did that.

The code doesn't use any library (except for the LCD) and runs exactly as is, with pins according to the schematics.

This is a little bit complicated, and if I was to do it again, I would only keep a small LCD for antenna position, and skip the manual commands. I'd put 2 LEDs for motors supervision, and the rest of movement and monitoring would be done by the software.

You will find here two versions: One for DC motors, with the advantage of using softer/smoother movement (PWM controlled), and one for AC motors (just relays). The later one can be interfaced with existing commercial antenna rotators.

After you finish the construction, you must apply the calibration procedures. The potentiometer calibration ensures correct reading of 0-359deg. / 0-90deg., no matter what kind of potentiometer you're using. The motor calibration is only for DC, and tunes the soft stop feature. This is only necessary if you don't like the default settings.

I am deeply grateful to all the people who sent me feedback and suggestions, contributing to the improvement of this project.

Give me an email if you want more information, because this platform doesn't inform me of new comments, dunno why. I'll try to solve small problems the best I can. YO3RAK@gmail.com

More detailed explanations in the videos.

Code

Arduino UNO antenna rotator - April 2021Arduino
This code is for DC motors, with soft stop PWM output
/*  AZ/EL Antenna Rotator controller for Arduino - DC motors
 *  ========================================================
 *  Uses EasyComm protocol for computer - Tracking Software
 *  Manual command by means of two rotary encoders AZ - EL
 *  
 *  Viorel Racoviteannu
 *  https://www.youtube.com/channel/UCiRLZX0bV9rS04BGAyUf-fA
 *  https://racov.ro
 *  YO3RAK@gmail.com
 *  
 * I cannot take any responsibility for missuse of this code
 * or any kind of damage it may occur from using this code.
 * 
 * dec 2020 v2 - improved serial comm stability
 * january 2021 - fixed AZ, EL tolerances for motor activation
 * apr 2021 - improved serial comm stability
 */
 
#include <Wire.h> // Library for I2C communication
#include <LiquidCrystal_I2C.h> // Library for LCD
// Wiring: SDA pin is connected to A4 and SCL pin to A5.
// Connect to LCD via I2C, default address 0x27 (A0-A2 not jumpered)
LiquidCrystal_I2C lcd(0x27, 16, 2); // address, chars, rows.

// declaring custom symbol for up/down arrow
 byte DownArrow[8] = {
  B00000,
  B00100,
  B00100,
  B00100,
  B10101,
  B01110,
  B00100,
  B00000
};
 byte UpArrow[8] = {
  B00000,
  B00100,
  B01110,
  B10101,
  B00100,
  B00100,
  B00100,
  B00000
};

// ANTENNA potentiometers CALIBRATION
  int AzMin = 90;
  int AzMax = 1000;
  int ElMin = 10;
  int ElMax = 992;

// Allowed error for which antennna won't move
  int AzErr = 5;
  int ElErr = 4;
  
// Azim encoder variables
  enum AzPinAssignments {
  AzEncoderPinA = 2,   // encoder right
  AzEncoderPinB = 3,   // encoder left
  AzClearButton = 4};    // encoder push
  unsigned int lastReportedPos = 1;   // change management
  static boolean rotating = false;    // debounce management
  // interrupt service routine vars
  boolean A_set = false;
  boolean B_set = false;
  
//Elev encoder variables
  enum ElPinAssignments{
  ElEncoderPinA = 6,   // encoder right
  ElEncoderPinB = 5,   // encoder left
  ElClearButton = 7};    // encoder push
  int aState;
  int aLastState; 
  
// other variables
  int AzPotPin = A0;   // select the input pin for the azim. potentiometer
  int AzRotPin = 12;   // select the out pin for rotation direction
  int AzPWMPin = 11;   // select the out pin for azimuth PWM command
  int TruAzim = 0;     // calculated real azimuth value
  int ComAzim = 0;     // commanded azimuth value
  int OldTruAzim = 0;  // to store previous azimuth value
  int OldComAzim = 0;
  char AzDir;          // symbol for azim rot display
  int AzEncBut = 1;    // variable to toggle with encoder push button 

  int ElPotPin = A1;   // select the input pin for the elev. potentiometer
  int ElRotPin = 13;   // select the out pin for elevation rotation direction
  int ElPWMPin = 10;   // select the out pin for elevation rotation PWM command
  int TruElev = 0;     // calculated real elevation value
  int ComElev = 0;     // commanded elevation value
  int OldTruElev = 0;  // to store previous elevation value
  int OldComElev = 0;
  char ElDir;          // symbol for elev. rot display
// flags for AZ, EL tolerances
  bool AzStop = false;
  bool ElStop = false;
  
//averaging loop
  const int numReadings = 25;
  int readIndex = 0;             // the index of the current reading  
  int azimuth[numReadings];      // the readings from the analog input
  int elevation[numReadings];
  int totalAz = 0;               // the running total
  int totalEl = 0;

// variables for serial comm
  String Azimuth = "";
  String Elevation = "";
  String ComputerRead;
  String ComputerWrite;
  bool AZser = false;
  bool ELser = false;
  bool ANTser = false;
  
void setup() {
  Serial.begin(9600);
// Initiate the LCD:
  //lcd.begin(16,2);
  lcd.init();
  lcd.backlight();

//creating custom symbol for up/dwn arrow
  lcd.createChar(1, DownArrow);
  lcd.createChar(2, UpArrow);
  
// pin declaration
  pinMode(AzRotPin, OUTPUT);       //declaring  azim. rotation direction Pin as OUTPUT
  pinMode(AzPWMPin, OUTPUT);       //declaring  azimuth PWM command Pin as OUTPUT
  pinMode(ElRotPin, OUTPUT);       //declaring  elev. rotation direction Pin as OUTPUT
  pinMode(ElPWMPin, OUTPUT);
  pinMode(AzPotPin, INPUT);
  pinMode(ElPotPin, INPUT);
  pinMode(AzEncoderPinA, INPUT);
  pinMode(AzEncoderPinB, INPUT);
  pinMode(AzClearButton, INPUT);
  pinMode(ElEncoderPinA, INPUT);
  pinMode(ElEncoderPinB, INPUT);
  pinMode(ElClearButton, INPUT);

// AzEncoder pin on interrupt 0 (pin A)
  attachInterrupt(0, doEncoderA, CHANGE);
// AzEncoder pin on interrupt 1 (pin B)
  attachInterrupt(1, doEncoderB, CHANGE);
// Reads the initial state of the ElEncoderPinA
   aLastState = digitalRead(ElEncoderPinA);

// write on display name and version
  lcd.setCursor(0, 0);          // Set the cursor on the first column first row.(counting starts at 0!)
  lcd.print("EasyCom AntRotor"); // display "..."
  lcd.setCursor(0, 1);          // Set the cursor on the first column the second row
  lcd.print("*Racov* Jan.2021");
  delay(2000);                  // keep for 2 seconds

// display Azim. and Elev. values
  lcd.setCursor(0, 0);
  lcd.print("Azm.---" + String(char(223)) + "=Cd.---" + String(char(223)));  // char(223) is degree symbol
  lcd.setCursor(0, 1); 
  lcd.print("Elv. --" + String(char(223)) + "=Cd. --" + String(char(223)));

// this is to set azim-command the same value as real, not to jerk the antenna at start-up
  TruAzim = (map(analogRead(AzPotPin), AzMin, AzMax, 0, 359));      // azimuth value 0-359
  if (TruAzim<0) {TruAzim=0;}
  if (TruAzim>359) {TruAzim=359;}  // keep values between limits
  TruElev = (map(analogRead(ElPotPin), ElMin, ElMax, 0, 90));       // elev value 0-90
  if (TruElev<0) {TruElev=0;}
  if (TruElev>90) {TruElev=90;}    // keep values between limits

// initialize all the readings
  for (int thisReading = 0; thisReading < numReadings; thisReading++) {
    azimuth[thisReading] = 0;
    elevation[thisReading] = 0;
  }
  
  ComAzim = TruAzim;
  ComElev = TruElev;
  OldTruAzim = TruAzim;
  OldComAzim = ComAzim;
  OldTruElev = TruElev;
  OldComElev = TruElev;
  DisplTruAzim();
  DisplComAzim();
  DisplTruElev();
  DisplComElev();
}
  
void loop() {
// AZIMUTH AVERAGING LOOP
  totalAz = totalAz - azimuth[readIndex];
  // read from the sensor:
  azimuth[readIndex] = (map(analogRead(AzPotPin), AzMin, AzMax, 0, 359));
  // add the reading to the total:
  totalAz = totalAz + azimuth[readIndex];
  // advance to the next position in the array:
  readIndex = readIndex + 1;
  // if we're at the end of the array, wrap around to the beginning:
  if (readIndex >= numReadings) {readIndex = 0;}
  // calculate the average:
  TruAzim = totalAz / numReadings;  
  if (TruAzim<0) {TruAzim=0;}
  if (TruAzim>359) {TruAzim=359;}  // keep values between limits
    
//ELEVATION AVERAGING LOOP
  totalEl = totalEl - elevation[readIndex];
  elevation[readIndex] = (map(analogRead(ElPotPin), ElMin, ElMax, 0, 90));
  totalEl = totalEl + elevation[readIndex];
  readIndex = readIndex + 1;
  if (readIndex >= numReadings) {readIndex = 0;}
  TruElev = totalEl / numReadings;
  if (TruElev<0) {TruElev=0;}
  if (TruElev>90) {TruElev=90;}    // keep values between limits
  
// update antenna position display
  if ((millis()%500)<10){                       //not to flicker the display
    if (OldTruAzim!=TruAzim) {DisplTruAzim();}
    if (OldTruElev!=TruElev) {DisplTruElev();}
  }

// this is to read the command from encoder
  ReadAzimEncoder();
  ReadElevEncoder();
  
// every 2 secons looking for serial communication
  if ((millis()%2000)<1000){
    if (Serial.available()) {
      SerComm();
    }
  }

// update target position display
  if (ComAzim != OldComAzim) {DisplComAzim();}
  if (ComElev != OldComElev) {DisplComElev();}

// this is to rotate in azimuth
  if (TruAzim == ComAzim) {                // if equal, stop moving
    AzStop = true;
    analogWrite(AzPWMPin, 0);
    lcd.setCursor(8, 0);
    lcd.print("=");
  }
    else if ((abs(TruAzim - ComAzim)<=AzErr)&&(AzStop == false)) {  // if in tolerance, but it wasn't an equal, rotate
      AzimRotate();}
    else if (abs(TruAzim - ComAzim)>AzErr){   // if target is off tolerance
      AzStop = false;                     // it's not equal
      AzimRotate();                       // rotate
    }

// this is to rotate in elevation
  if (TruElev == ComElev) {                // if equal, stop moving
    ElStop = true;
    analogWrite(ElPWMPin, 0);
    lcd.setCursor(8, 1);
    lcd.print("=");
  }
    else if ((abs(TruElev - ComElev)<=ElErr)&&(ElStop == false)) {  // if in tolerance, but it wasn't an equal, rotate
      ElevRotate();}
    else if (abs(TruElev - ComElev)>ElErr){   // if target is off tolerance
      ElStop = false;                         // it's not equal
      ElevRotate();                           // rotate
    }

// this is to interpter x10 multiplication, even if Tru position = Com position
  while (AzEncBut == 10) {       // while toggled to x10
    analogWrite(AzPWMPin, 0);    // deactivate pin azim PWM command
    analogWrite(ElPWMPin, 0);    // deactivate pin elev PWM command
    AzDir = char(42);            // display direction "*"
    lcd.setCursor(8, 0);
    lcd.print(String(AzDir));
    ReadAzimEncoder();
    if (OldComAzim != ComAzim){   // update display only if numbers change
      lcd.setCursor(12, 0);
    if (ComAzim<10) {
      lcd.print("00");
      lcd.print(ComAzim);}
    else if (ComAzim<100) {
      lcd.print("0");
      lcd.print(ComAzim);}
    else {lcd.print(ComAzim);}
    OldComAzim = ComAzim;
    }
    delay(10);
    }

//  delay(50);                      //pause the program for x ms
}

//____________________________________________________
// ___________procedures definitions__________________

void DisplTruAzim() {
  lcd.setCursor(4, 0);
  if (TruAzim<10) {
      lcd.print("00");
      lcd.print(TruAzim);}
    else if (TruAzim<100) {
      lcd.print("0");
      lcd.print(TruAzim);}
    else {lcd.print(TruAzim);}
  OldTruAzim = TruAzim;
  
// ************** FOR CALIBRATION PURPOSES **************
//  Serial.print ("Az ");
//  Serial.println (analogRead(AzPotPin));
}

void DisplTruElev(){
  lcd.setCursor(5, 1);
  if (TruElev<10) {
      lcd.print("0");
      lcd.print(TruElev);}
    else {lcd.print(TruElev);}
  OldTruElev = TruElev;

// ************** FOR CALIBRATION PURPOSES **************
//  Serial.print ("El ");
//  Serial.println (analogRead(ElPotPin));
}

void DisplComAzim(){
  lcd.setCursor(12, 0);
  if (ComAzim<10) {
      lcd.print("00");
      lcd.print(ComAzim);}
    else if (ComAzim<100) {
      lcd.print("0");
      lcd.print(ComAzim);}
    else {lcd.print(ComAzim);}
  OldComAzim = ComAzim;
}

void DisplComElev(){
  lcd.setCursor(13, 1);
  if (ComElev<10) {
      lcd.print("0");
      lcd.print(ComElev);}
    else {lcd.print(ComElev);}
  OldComElev = ComElev;
}

void ReadElevEncoder() {
  aState = digitalRead(ElEncoderPinA); // Reads the "current" state of the ElEncoderPinA
   // If the previous and the current state of the ElEncoderPinA are different, that means a Pulse has occured
   if (aState != aLastState){     
     // If the ElEncoderPinB state is different to the ElEncoderPinA state, that means the encoder is rotating clockwise
     if (digitalRead(ElEncoderPinB) != aState) { 
        ComElev ++;
     } else {
       ComElev --;
     }
     if (ComElev <0) {ComElev = 0;}
     if (ComElev >90) {ComElev = 90;}
   }
   aLastState = aState; // Updates the previous state of the ElEncoderPinA with the current state
}

void ReadAzimEncoder() {
  rotating = true;  // reset the debouncer
  if (lastReportedPos != ComAzim) {
    lastReportedPos = ComAzim;
  }
  if (digitalRead(AzClearButton) == LOW )  {      // if encoder switch depressed
    delay (250);                                  // debounce switch 
    if (AzEncBut == 1){
      AzEncBut = 10;
      ComAzim = int(ComAzim/10)*10;
      AzDir = char(42);
    }
      else {
        AzEncBut = 1;
        AzDir = char(61);
    }
    lcd.setCursor(8, 0);
    lcd.print(String(AzDir));
  }
}

// Interrupt on A changing state
void doEncoderA() {
  // debounce
  if ( rotating ) delay (1);  // wait a little until the bouncing is done
  // Test transition, did things really change?
  if ( digitalRead(AzEncoderPinA) != A_set ) {   // debounce once more
    A_set = !A_set;
    // adjust counter + if A leads B
    if ( A_set && !B_set )
      ComAzim += AzEncBut;
      ComAzim = ((ComAzim + 360) % 360);     // encoderPos between 0 and 359 deg.
    rotating = false;  // no more debouncing until loop() hits again
  }
}
// Interrupt on B changing state, same as A above
void doEncoderB() {
  if ( rotating ) delay (1);
  if ( digitalRead(AzEncoderPinB) != B_set ) {
    B_set = !B_set;
    //  adjust counter - 1 if B leads A
    if ( B_set && !A_set )
      ComAzim -= AzEncBut;
      ComAzim = ((ComAzim + 360) % 360);     // encoderPos between 0 and 359 deg.
    rotating = false;
  }
 }

void AzimRotate() {
    if ((ComAzim-TruAzim) > (TruAzim-ComAzim)) {      // this to determine direction of rotation
        digitalWrite(AzRotPin, LOW);                  // deactivate rotation pin - rotate right
        AzDir = char(126);}                           // "->"
      else {
        digitalWrite(AzRotPin, HIGH);                 // activate rotation pin - rotate left
        AzDir = char(127);}                           // "<-"
 // this activates azim PWM pin with soft stop
    if ((abs(ComAzim-TruAzim)) < 6) {                 // the difference between command and true azim
        analogWrite(AzPWMPin, (255*0.3));}      // if less then 6 deg., 30% power         
      else if ((abs(ComAzim-TruAzim)) < 10) {
        analogWrite(AzPWMPin, (255*0.6));}      // if less then 10 deg., 60% power        
      else {
        analogWrite(AzPWMPin, 255);}          // more than 10 deg. diff., full power
  lcd.setCursor(8, 0);
  lcd.print(String(AzDir));
}

void ElevRotate() {
// this to determine direction of rotation
    if ((ComElev-TruElev) > (TruElev-ComElev)) {
        digitalWrite(ElRotPin, LOW);                  // deactivate rotation pin - rotate right
        lcd.setCursor(8, 1);
        lcd.write(2);}                                // arrow up
     else {
        digitalWrite(ElRotPin, HIGH);                 // activate rotation pin - rotate left
        lcd.setCursor(8, 1);
        lcd.write(1);}                                // arrow down
 // this activates elev PWM pin with soft stop
    if ((abs(ComElev-TruElev)) < 8) {       // the difference between command and true elev
      analogWrite(ElPWMPin, 225*0.7);}        // if less then 8 deg., 70% power          
    else {
      analogWrite(ElPWMPin, 255);}          // more than 8 deg. diff., full power
}

void SerComm() {
  // initialize readings
  ComputerRead = "";
  Azimuth = "";
  Elevation = "";

  while(Serial.available()) {
    ComputerRead= Serial.readString();  // read the incoming data as string
//    Serial.println(ComputerRead);     // echo the reception for testing purposes
  }
  
// looking for command <AZxxx.x>
    for (int i = 0; i <= ComputerRead.length(); i++) {
     if ((ComputerRead.charAt(i) == 'A')&&(ComputerRead.charAt(i+1) == 'Z')){ // if read AZ
      for (int j = i+2; j <= ComputerRead.length(); j++) {
        if (isDigit(ComputerRead.charAt(j))) {                                // if the character is number
          Azimuth = Azimuth + ComputerRead.charAt(j);
        }
        else {
          break;
        }
      }
     }
    }
    
// looking for command <ELxxx.x>
    for (int i = 0; i <= ComputerRead.length(); i++) {
      if ((ComputerRead.charAt(i) == 'E')&&(ComputerRead.charAt(i+1) == 'L')){ // if read EL
        for (int j = i+2; j <= ComputerRead.length(); j++) {
          if (isDigit(ComputerRead.charAt(j))) {                               // if the character is number
            Elevation = Elevation + ComputerRead.charAt(j);
          }
          else {
            break;
          }
        }
      }
    }
    
// if <AZxx> received
    if (Azimuth != ""){
      ComAzim = Azimuth.toInt();
      ComAzim = (ComAzim+360)%360;     // keeping values between limits
      }

// if <ELxx> received
    if (Elevation != ""){
      ComElev = Elevation.toInt();
      if (ComElev<0) { ComElev = 0;}
      if (ComElev>90) {                //if received more than 90deg. elevation
        ComElev = 180-ComElev;
        ComAzim = (ComAzim+180)%360;
      }
    }

// looking for <AZ EL> interogation for antenna position
  for (int i = 0; i <= (ComputerRead.length()-4); i++) {
    if ((ComputerRead.charAt(i) == 'A')&&(ComputerRead.charAt(i+1) == 'Z')&&(ComputerRead.charAt(i+3) == 'E')&&(ComputerRead.charAt(i+4) == 'L')){
    // send back the antenna position <+xxx.x xx.x>
      ComputerWrite = "+"+String(TruAzim)+".0 "+String(TruElev)+".0";
      Serial.println(ComputerWrite);
    }
  }
}
Potentiometer calibration procedureArduino
AZ / EL Potentiometers limit calibration PROCEDURE for displaying the correct antenna angles and rotation limits ( 0-359ᴼ / 0-90ᴼ)
This is plain text, not a code :)
AZ / EL Potentiometers limit calibration PROCEDURE  ( 0-359 /  0-90)
 
1. Open the code in Arduino and
 - Look for 
void DisplTruAzim() {
...
//  Serial.print ("Az ");
//  Serial.println (analogRead(AzPotPin));

Uncoment these lines

 - Look for 
void DisplTruElev() {
...
//  Serial.print ("El ");
//  Serial.println (analogRead(ElPotPin));

Uncoment these lines, too.

2. Upload the code and open the serial monitor. There you will see a lot of numbers;

3. With the help of the encoders, move the antenna to minimum values, 0 in azimuth and 0 in elevation.
- Write down the values for Azimuth and Elevation. (in my case it was AzMin=90, ElMin=10)
- These are the input values read by Arduino, not the real angles;

4. Move the antenna again to maximum values,  359 in azimuth and 90 in elevation.
- Again, write down the values for Azimuth and Elevation. (in my case it was AzMax=1000, ElMax=992);

5. Look in the code, at the beginning, for the section

// ANTENNA potentiometers CALIBRATION
  int AzMin = 90;
  int AzMax = 1000;
  int ElMin = 10;
  int ElMax = 992;

- Here input the values you wrote down for each situation;

6. Now it is no longer necessary to send this on serial, so you have to comment back these lines:
- Look for 
void DisplTruAzim() {
...
  Serial.print ("Az ");
  Serial.println (analogRead(AzPotPin));

These lines have to be commented like this

  // Serial.print ("Az ");
  // Serial.println (analogRead(AzPotPin));

 

Repeat the same thing for 
void DisplTruElev(){
...
  // Serial.print ("El ");
  // Serial.println (analogRead(ElPotPin));

7. Now upload again the code.

That's all. Now, in the serial monitor, there should be no more numbers.
*************************************************************************
For the tracking algorithm, the antenna goes on target and only re-aligns after a certain error.

You can adjust the tolerances to suit your preferences. Now there is 5 in azimuth and 4 in elevation.
Just go at the top of the code and search for
// Allowed error for which antenna won't move
int AzErr = 5;
int ElErr = 4;
and change them according to your needs.

Schematics

Electric Diagram for DC motors
Connection of all the modules, encoders, LCD, relays, MosFet etc,
Drawing1 r95c2ok2aa

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