Potentiometer to control Stepper Motor Position

[Brian McMillion]

Hello. I 've been experimenting with the AccelStepper library which is great by the way! I'm trying to use a Potentiometer to set the position of a stepper motor. Below is my current code.

/*Sketch to use a Potentiometer to step the position of a stepper motor
  The stepper should move at a constant speed to each newly set position
*/

#include <AccelStepper.h>

// Setting Motor Connections
const int dirPin = 4;   //GPIO Pin4
const int stepPin = 2;  //GPIO Pin2

// Create an instance
AccelStepper motor1(AccelStepper::DRIVER, stepPin, dirPin, 0xff, 0xff, false);
// This instance form prevents the interface pins from being initialized SEE SETUP void()

// POT reading must move out of this band to cause motion-avoid jidder
#define DEADBAND 5

// Define the analog pin for reading the control voltage
#define ANALOG_IN A6

void setup() {
  Serial.begin(115200);
  motor1.setPinsInverted(true, false, true);
  motor1.setEnablePin(15);
  motor1.disableOutputs();
  motor1.setMaxSpeed(400.0);
}

void loop() {
  static int oldReading = 0;      // old ADC reading
  static bool printOnce = false;  // print flag
  motor1.enableOutputs();
  // Read new position - four averages cut noise.
  int analog_in = (analogRead(ANALOG_IN) + analogRead(ANALOG_IN) + analogRead(ANALOG_IN) + analogRead(ANALOG_IN)) / 4;
  if ((analog_in > (oldReading + DEADBAND)) || (analog_in < (oldReading - DEADBAND))) {
    motor1.moveTo((long)analog_in);
    motor1.setSpeed(100.0);  // set speed MUST be called after calling moveTo -
    //                         moveTo calculates a new speed! Needed if runSpeedToPosition is used.
    oldReading = analog_in;
    printOnce = true;
  }

  if (motor1.distanceToGo() != 0) {
    motor1.runSpeedToPosition();
  }
  else if (printOnce == true) {
    Serial.print(oldReading);
    Serial.print("   ");
    Serial.print(motor1.currentPosition());
    Serial.print("   ");
    Serial.println(motor1.targetPosition());
    printOnce = 0;
    while (motor1.distanceToGo() == 0){
      motor1.disableOutputs();
    }
  }
 }

The problem is when I first run the program, the stepper moves to the position according to the Pot. However, after it reaches that position, if I move the Pot to set a "new" position nothing happens. It's running the program once instead of allowing a new Pot setting to set a new Stepper position, which is my goal.

Any guidance will  be greatly appreciated.

Thanks, Brian.

[Jim Larson]

I haven't had tome to actually run your code yet, Brian, but I think the while statement in your else if (printOnce==true) clause will stop further execution of your code. Try changing it to an if instead of a when, and possibly repositin it.

HTH

                 -jim

[Brian McMillion]

Thank you Jim for the suggestion. I moved "motor1.distance ToGo() instruction to  "else if" and moved the print instructions to be the  last in the loop. It worked but raised another challenge. The analog_in is not stable even with the deadpan.

Leaving the POT at one position, there is enough variance in the reading to cause the motor to move. 

Brian

[Jim Larson]

Increase the deadband? Increase the number of averages? Make sure the powersupply for the pot is  isolated from the motor power supply?

I've found that the motor can put a lot of noise on the power supply.

           -jim