Stepper Motor and IR Sensor Programming

Projects Programming
1

Parts:
Stepper Motor (1.8 degrees per step)
GP2D15 IR Sensor

I am trying to write a program that rotates the stepper motor 360 degrees from 10 cm to 80 cm (the effective range on our IR Sensor). If you start at 10 cm and move 80 cm away from the IR sensor, the stepper motor should have rotated a full 360 degrees. The catch is, though, that if you stop moving away from the sensor, the motor will stop spinning. Then, if you start to move closer to the IR sensor it will reverse directions and rotate the other way until it returns to its original position at 10 degrees.

I have the IR sensor working properly, with a distance equation and everything. I also have the code to get the stepper motor to spin 360 degrees using 1/8th of a step. The problem I am having is getting them to work together to spin 360 degrees, reverse, and stop.

This is the code we have currently:

int step_pin = 3;
int dir_pin = 2;
float IRsens;
float voltage;
float distance;
float dist_new;
float dist_old;
float dir;
 
void setup()
{
  Serial.begin(9600);
    
  pinMode(3,OUTPUT);
  pinMode(2,OUTPUT);
}

void loop()
{ 
  
 
  
  //delay(500);
  
  
  for(int i=0; i <=1600 ; i++)
  {
    IRsens = analogRead(0);
    voltage = IRsens * 5/1023;
    distance = 106.02*exp(-1.117*voltage);
    dist_new = distance;
    dir = (dist_new - dist_old);
    
    Serial.print("Distance cm = ");
    Serial.println(distance);

    Serial.print("Distance cm = ");
    Serial.println(dist_new);

    Serial.print("Distance cm = ");
    Serial.println(dist_old);

    Serial.print("Direction = ");
    Serial.println(dir);
    Serial.println(" ");
    
    delay(1000);
    
    if (dir > 0)
    {
      digitalWrite(dir_pin, HIGH);  
      
      digitalWrite(step_pin, LOW);
      delay(10);
    
      digitalWrite(step_pin, HIGH);
      delay(10);
    }
    
    if (dir < 0)
    {
      digitalWrite(dir_pin, LOW);  
      
      digitalWrite(step_pin, LOW);
      delay(10);
    
      digitalWrite(step_pin, HIGH);
      delay(10);
    }
    
    if (dir == 0)
    {
      digitalWrite(dir_pin, LOW);  
      
      digitalWrite(step_pin, LOW);
      delay(10);
    
      digitalWrite(step_pin, LOW);
      delay(10);
    }
      dist_old = dist_new;
  }

}
2

I am trying to write a program that rotates the stepper motor 360 degrees from 10 cm to 80 cm (the effective range on our IR Sensor).

How does the motor rotating change its distance from the IR sensor. Whats the IR sensors target? Why are you doing lots of conversions is stend of looking up the required values on the distance/reading graph provided with the sensor.

Mark

3

Does your stepper driver need high or low pulses to cause a step? I would write a single step like this

digitalWrite(stepPin, HIGH);
   delayMicroseconds(20); // may not be necessary at all
   digitalWrite(stepPin, LOW);
   delay(20);  // the number of milliseconds between steps to give the speed you want

You have virtually identical code in several places. It's very easy for errors to creep in when you modify one place and forget to carry the change to all the others. I would create a function so that you only need one copy of the code.

It will also get a huge chunk of code out of loop() so you can concentrate on the logic that is causing you a problem.

I think your code needs to record the "position" of the motor and then use that, compared to the distance detected by the sensor, to decide whether and how the motor needs to move.

...R