control stepper motor by optical encoder

Hello everyone. used a simple code to print to a DTG printer. but when I started printing blanks, or with a little filling of the picture, the picture began to shrink and stretch. since the synchronization of the encoder with the motor is not in real time, it can be seen from the code. did a bunch of work on the rest of the sensor signal code on the printer. and it turned out during the test. who can suggest or help how to implement. synchronization of an optical encoder with a stepper motor in real time with a full transfer of speed (acceleration). thank you all for your help

reading encoder

void encoderPinChangeA(){
    if (digitalRead(encoder_a) == digitalRead(encoder_b)){
        encoder--;
    }
    else{
        encoder++;
    }
}


void encoderPinChangeB(){
    if (digitalRead(encoder_a) != digitalRead(encoder_b)){
        encoder--;
    }
    else{
        encoder++;
    }
}

stepper control

if (encoder > 0){
         digitalWrite(motor_direction, HIGH);  
         digitalWrite(motor_step, HIGH);      
         digitalWrite(motor_step, LOW);       
         _delay_us(800);                      
         motor_position++;                     
         encoder = 0;                         
      }
      else if (encoder < 0){
         digitalWrite(motor_direction, LOW);  
         digitalWrite(motor_step, HIGH);      
         digitalWrite(motor_step, LOW);      
         _delay_us(800);                   
         motor_position--;                    
         encoder = 0;                          
       }

As I understand it, while the delay 800 encoder is not read as there is a delay. but if even to implement on millis there the coefficient needs to be put down? as there should be synchronization. information has not yet been found. I ask for help.

I don't even think about software protection against pulsation, interference or inertia and other things yet. for now I need to make friends with an encoder

motor_position++;

also I do not understand why this line may have been an upgrade but not about it now

0 shabaz over 1 year ago

Hi,

There are many examples of stepper motor driving with Arduino, and many examples of reading encoders. If you compare your code, you'll easily spot differences. You shouldn't be trying to reinvent the wheel entirely unless you have lots more familiarity with code, motors and encoders. I think you'd benefit greatly by looking at established ways of reading encoder positions and driving motors. Also a 'scope would help. And consider how a motor works (how long do you think power needs to be applied to make it rotate?). And understand the order of your code excecution and the approximate time each instruction takes to execute. These are all things you can easily experiment and self-learn, along with a programming book. Use an LED if it is easier, to see when power is being applied to your motor, and see if it makes sense (ideally you'd also be using a 'scope).
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0 balexfox over 1 year ago

thank you to autor i find what i look for

#include <AccelStepper.h>

#define encoder_pin_A 8
#define encoder_pin_B 9
int encoder_pin_A_last = LOW;
int encoder_pos = 0;
int n = LOW;

#define stepper_pin_step 6
#define stepper_pin_dir  5

// Enc have 24 steps per revolution
// The motor have 800 steps per revolution
// Want: 1 encoder rev = 1 stepper rev
// 800 / 24 = 33.3333333333...
float steps_per_pulse = 33.3333333333;

AccelStepper stepper(AccelStepper::DRIVER, stepper_pin_step, stepper_pin_dir);

void setup() {
  stepper.setMaxSpeed(800.0);
  stepper.setAcceleration(300.0);
   
  pinMode(encoder_pin_A, INPUT_PULLUP);
  pinMode(encoder_pin_B, INPUT_PULLUP);
}

void loop() {
  // read encoder
  n = digitalRead(encoder_pin_A);
   
  if ((encoder_pin_A_last == LOW) && (n == HIGH)) {
    if (digitalRead(encoder_pin_B) == LOW) {
      encoder_pos--;
    } else {
      encoder_pos++;
    }

    // set stepper to the new calculated position
    stepper.moveTo((long) round(encoder_pos*steps_per_pulse));
  }
   
  encoder_pin_A_last = n;

  stepper.run();
}

link

https://www.norwegiancreations.com/2019/08/arduino-as-a-stepper-motor-controller-jogging-with-acceleration/