Stepper Motor Radar

Projects General Guidance
1

I have a project that needs to have an Ultrasonic detector attached to the to the top of a stepper motor. I however I want the radar to mover either between 15 - 165 degrees or 0 and 180. But I can only get the motor to rotate a full 360. I can see when the motor is delaying when it should change directions but it stays in one direction.

If the problem is not code then I believe it might be the wires. But when I follow the datasheet and pin input the stepper moves too slow and still does't change direction.

I have attached the code here and a hand drawn schematic of what I think might be a wiring issue.

#include <Stepper.h>. 
// Defines Ti and Echo pins of the Ultrasonic Sensor
const int trigPin = 10;
const int echoPin = 11;
const int steps = 800;
// Variables for the duration and the distance
long duration;
int distance;
Stepper myStepper(steps , 2,4,3,5); 
void setup() {
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
  pinMode(echoPin, INPUT); // Sets the echoPin as an Input
  Serial.begin(9600);
   // set the speed at 60 rpm:
  myStepper.setSpeed(20);
  // initialize the serial port:
  Serial.begin(9600);
}


void loop() {
  // rotates the stepper motor from 15 to 165 degrees
  for(int i=0;i<=165;i++){  
  myStepper.step(i);
  delay(30);
  distance = calculateDistance();// Calls a function for calculating the distance measured by the Ultrasonic sensor for each degree
  
  Serial.print(i);
  Serial.print(","); 
  Serial.print(distance);
  Serial.print(".");
  }
  // Repeats the previous lines from 165 to 15 degrees  
  for(int i=165;i>=15;i--){
  myStepper.step(i);
  delay(30);
  distance = calculateDistance();
  Serial.print(i);
  Serial.print(",");
  Serial.print(distance);
  Serial.print(".");
  }
}
// Function for calculating the distance measured by the Ultrasonic sensor
int calculateDistance(){ 
  
  digitalWrite(trigPin, LOW); 
  delayMicroseconds(2);
  // Sets the trigPin on HIGH state for 10 micro seconds
  digitalWrite(trigPin, HIGH); 
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH); // Reads the echoPin, returns the sound wave travel time in microseconds
  distance= duration*0.034/2;
  return distance;
}

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2 


#include <Stepper.h>. 
Stepper myStepper(steps , 2,4,3,5); 

void loop() {
  // rotates the stepper motor from 15 to 165 degrees
  for(int i=0;i<=165;i++){  
  myStepper.step(i);

The problem is that you are trying to use a stepper like it was a servo. The stepper moves to a relative position. If you tell it to go to 80 it goes 80 steps forward. If you tell it to go to 80 again it moves ANOTHER 80 steps. A servo moves to an absolute position. If you tell it to go to 80 it goes to 80°. If you tell it to go to 80 again it stays right where it is because it is already at 80°.

You need to remember where the stepper is and tell it how many steps to move to get to where you want it. That will depend on the angular distance you want it to move the number of steps in that angle.

3

Ok I understand that. I was using a servo previously. But how would i change it then from

for (int i = 0; i <= 165; i++)

I'm guessing that's the issue right? I am new to this and it's a project for my engineering class. But I haven't had any real education on Sketches.

4

I have figured it out.

I coded this instead. Thanks for your help!

  for(int i=steps;i;)
  {  
  myStepper.step(steps);
  delay(30);
  distance = calculateDistance();
  //Serial.print(i); 
  Serial.print(distance);
  Serial.println(" cm");

    
  myStepper.step(-steps);
  delay(30);
  distance = calculateDistance();
  //Serial.print(i);
  Serial.print(distance);
  Serial.println(" cm");