Wednesday, April 11, 2018

Arduino Star Tracker - How to track stars with Arduino

Star Tracking is a beautiful hobby. You can learn a lot of scientific information while you enjoy spending time doing what you really love.

Star gazing or star tracking can be virtually practiced by anyone.

But when it comes to reality it’s hard to make due to the fact that astronomy tools and gadgets are a little bit expensive.

There are some sophisticated astronomy gadgets like star tracking telescopes that can cost hundreds of dollars.

GoTo Telescope is a famous brand of star tracking telescopes.

Today, we have a project that makes a clone for the GoTotelescope.

This project is based on Arduino and can be built at home.

The project is a laser star tracker based on Arduino for controlling stepper motors to move the laser beam.

Degrees of rotation are calculated using 3axis gyroscope which sends data to another Arduino.

The two Arduino boards work in master/slave configuration.

Master Arduino board control stepper motors and slave Arduino board read position data from gyroscope and send them to the master board.

Components:

2 Arduino boards

MPU 6050 Gyroscope

5 Stepper Motors

Connection

Code

Master module code:

/*
 This is the source code for the master-module of Star Track.
 Required Libraries:
 https://virtuabotix-virtuabotixllc.netdna-ssl.com...
 https://github.com/jrowberg/i2cdevlib/zipball/mas...

 Created 20 July 2016 by Görkem Bozkurt
 */
#include 
#include 
#include 
MPU6050 mpu;
//define RTC.
virtuabotixRTC myRTC(A0, A1, A2);
double M,Y,D,MN,H,S;
double A,B;
double location =32.88;//your longtitude
double LST_degrees;//variable to store local side real time(LST) in degrees.
double LST_hours;//variable to store local side real time(LST) in decimal hours.
unsigned long timer = 0;
float timeStep = 0.01;
// Pitch and Yaw values
double pitch = 0;
double yaw = 0;
double val = 0;//variable to store the user input DEC
double val2 = 0;//variable to store the user input RA
double temp = val2;//temporary value to store val2
const int stahp=7,stahp2=10;
const int cw=8,cw2=11;
const int ccw=6,ccw2=9;
void setup() {
    //set date-time according to (seconds, minutes, hours, day of the week, day of the month, month, year) 
    myRTC.setDS1302Time(00, 38, 23, 5, 27, 7, 2016);
    Serial.begin(115200);
    pinMode(stahp,OUTPUT);
    pinMode(cw,OUTPUT);
    pinMode(ccw,OUTPUT);
    pinMode(stahp2,OUTPUT);
    pinMode(cw2,OUTPUT);
    pinMode(ccw2,OUTPUT);
    delay(5000);//wait before starting
    while(!mpu.begin(MPU6050_SCALE_2000DPS, MPU6050_RANGE_2G))
    {
    }
    mpu.calibrateGyro();
    mpu.setThreshold(3);
}//--(end setup )---
void loop()
{
    //this will update the RA degrees with sidereal time 1degree at a time
    //this way the object or star on the sky is tracked.
    if( floor(LST_degrees)==LST_degrees ){ 
      if (LST_degrees>180){
        val2 = temp+(360-LST_degrees);
        }else{
        val2 = temp-LST_degrees;
        }
    }

    myRTC.updateTime();
    LST_time();
    recvdata();
    pitch_check();
    yaw_check();
    timer = millis();
    Vector norm = mpu.readNormalizeGyro();
    //I've put the sensor with a 90 degree angle on the setup due to
    //cable connection problems. Because of that the data values from the mpu6050 chip are
    //different in this case:
    //roll data(X-axis) is pitch.
    //pitch data(Y-axis) is yaw.
    yaw = yaw + norm.YAxis * timeStep;
    pitch = pitch + norm.XAxis * timeStep;
    Serial.print(" Yaw = ");
    Serial.print(yaw);
    Serial.print(" Pitch = ");
    Serial.print(pitch);
    Serial.print(" LST_d = ");
    Serial.print(LST_degrees);
    Serial.print(" LST_h = ");
    Serial.println(LST_hours);//local sidereal time in decimal hours.
    delay((timeStep*1000) - (millis() - timer));//timer for the gyro.
}
void recvdata(){
  //This function receives data from serial as (0.00,0.00)
  //splits it to strings by the comma ","
  //than converts them to doubles 
    if (Serial.available() > 0){
        String a= Serial.readString();
        String value1, value2;
        // For loop which will separate the String in parts
        // and assign them the the variables we declare
        for (int i = 0; i < a.length(); i++) {
            if (a.substring(i, i+1) == ",") {
                value2 = a.substring(0, i);
                value1= a.substring(i+1);
                break;
            }
        }
        val=90-value1.toFloat();
        val2=value2.toFloat();
        temp = val2;
    }
}
void pitch_check(){
    //check if pitch is high, low or equal to the user input
    //send commands to slave-module to start and stop motors
    if(floor(pitch*100)/100==floor(val*100)/100){
        digitalWrite(stahp,HIGH);
        }else{
        digitalWrite(stahp,LOW);
    }
    if(floor(pitch*100)        digitalWrite(cw,HIGH);
        }else{
        digitalWrite(cw,LOW);
    }
    if(floor(pitch*100)>floor(val*100)){
        digitalWrite(ccw,HIGH);
        }else{
        digitalWrite(ccw,LOW);
    }
}
void yaw_check(){
    //check if yaw is high, low or equal to the user input
    //send commands to slave-module to start and stop motors
    if(floor(yaw*100)==floor(val2*100)){
        digitalWrite(stahp2,HIGH);
        }else{
        digitalWrite(stahp2,LOW);
    }
    if(floor(yaw*100)        digitalWrite(cw2,HIGH);
        }else{
        digitalWrite(cw2,LOW);
    }
    if(floor(yaw*100)>floor(val2*100)){
        digitalWrite(ccw2,HIGH);
        }else{
        digitalWrite(ccw2,LOW);
    }
}
void LST_time(){
    //Calculates local sidereal time based on this calculation,
    //http://www.stargazing.net/kepler/altaz.html 
    M = (double) myRTC.month;
    Y = (double) myRTC.year;
    D = (double) myRTC.dayofmonth;
    MN = (double) myRTC.minutes;
    H = (double) myRTC.hours;
    S = (double) myRTC.seconds;
    A = (double)(Y-2000)*365.242199;
    B = (double)(M-1)*30.4368499;
    double JDN2000=A+B+(D-1)+myRTC.hours/24;
    double decimal_time = H+(MN/60)+(S/3600) ;
    double LST = 100.46 + 0.985647 * JDN2000 + location + 15*decimal_time;
    LST_degrees = (LST-(floor(LST/360)*360));
    LST_hours = LST_degrees/15;
}

Slave module code:

/*
this is the source code for the slave module of Star Track
Required Libraries:
http://www.airspayce.com/mikem/arduino/AccelStepper/AccelStepper-1.51.zip
Created 20 July 2016 by Görkem Bozkurt
 */
#include 
#define HALFSTEP 8
#include 
// Motor pin definitions
#define motorPin1  2     // IN1 on the ULN2003 driver 1
#define motorPin2  3     // IN2 on the ULN2003 driver 1
#define motorPin3  4     // IN3 on the ULN2003 driver 1
#define motorPin4  5     // IN4 on the ULN2003 driver 1


#define motorPin5  A0     // IN1 on the ULN2003 driver 1
#define motorPin6  A1     // IN2 on the ULN2003 driver 1
#define motorPin7  A2     // IN3 on the ULN2003 driver 1
#define motorPin8  A3     // IN4 on the ULN2003 driver 1
// Initialize with pin sequence IN1-IN3-IN2-IN4 for using the AccelStepper with 28BYJ-48
AccelStepper stepper1(HALFSTEP, motorPin1, motorPin3, motorPin2, motorPin4);
AccelStepper stepper2(HALFSTEP, motorPin5, motorPin7, motorPin6, motorPin8);


int stahp = 7,stahp2=10;
int cw = 6,cw2 = 11;
int ccw = 8,ccw2=9;


boolean stopped = false;
boolean stopped2 = false;
void setup() {
    stepper1.setMaxSpeed(1000.0);
    stepper2.setMaxSpeed(1000.0);
    pinMode(stahp2,INPUT);
    pinMode(cw2,INPUT);
    pinMode(ccw2,INPUT);
    pinMode(stahp,INPUT);
    pinMode(cw,INPUT);
    pinMode(ccw,INPUT);
}//--(end setup )---
void loop()
{
    motor_pitch();
    motor_roll();

    if(stopped==false){
        stepper1.run();
    }
    if(stopped2==false){
        stepper2.run();
    }
}
void motor_roll(){
    if(digitalRead(stahp)==HIGH){
        stopped = true;
    }else{ if(digitalRead(cw)==HIGH){
            stepper1.setSpeed(100);
            stopped = false;
        }
        if(digitalRead(ccw)==HIGH){
            stepper1.setSpeed(-100);
            stopped = false;
        }
    }
}
void motor_pitch(){
    if(digitalRead(stahp2)==HIGH){
        stopped2 = true;
    }else{ if(digitalRead(cw2)==HIGH){
            stepper2.setSpeed(100);
            stopped2 = false;
        }
        if(digitalRead(ccw2)==HIGH){
            stepper2.setSpeed(-100);
            stopped2 = false;
        }
    }

}