Stepper motor RPM variation bluetooth

Using Arduino Project Guidance
1

Hi everyone, I would like to comment on a rather peculiar situation, I am varying the RPM of a stepper motor nema 17 with driver a4988 in a cnc shield, and I am varying the rpm through an application in app inventor using bluetooth, with the application I vary well all speeds except when I put 50 rpm, the motor does not move, and it is strange because when I use the code without the use of bluetooth if I set rpm = 50; the motor does moves at that speed, at this point I would like ideas regarding this problem

#include <SoftwareSerial.h>
#include <AccelStepper.h>

// Definimos los pines utilizados
const int pinStep = 4;
const int pinDir = 7;
const int pinEnable = 8;
// Creamos un objeto de tipo AccelStepper
AccelStepper stepper = AccelStepper(1, pinStep, pinDir);
SoftwareSerial BTSerial(10, 11); // Creamos un objeto SoftwareSerial para la comunicación Bluetooth
int rpm = 0;
const int dir = -1; // 1 para CW, -1 para CCW
void setup() {
  // Configuramos los pines
  pinMode(pinEnable, OUTPUT);
  digitalWrite(pinEnable, LOW); // Habilitamos el driver
  
  // Configuramos el objeto AccelStepper
  stepper.setMaxSpeed(2000); // Velocidad máxima en RPM
  BTSerial.begin(38400); // Iniciamos la comunicación Bluetooth
}

void loop() {
char c;
  if(BTSerial.available()) {
    
    c = BTSerial.read();
    if (c == '1') {  
      rpm = 50;
    }
    if (c == '2') {  
      rpm = 150;
    }
    if (c == '3') {  
      rpm = 250;
    }
    if (c == '4') {  
      rpm = 350;
    }
    if (c == '5') {  
      rpm = 450;
    }
    if (c == '6') {  
      rpm = 550;
    }
       if (c == '7') {  
      rpm = 0;
    }
          
    stepper.setSpeed((dir * rpm / 60) * 200);
  }
  stepper.runSpeed();
}

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thank you

2

You running into integer truncation with rpm values below 60 with this equation. .setSpeed( ) takes a float for parameter so try

stepper.setSpeed((dir * (float) rpm / 60.0) * 200.0);

1 Like
3

Yeah men now it works thank you

4 
#include <SoftwareSerial.h>
#include <AccelStepper.h>

// Definimos los pines utilizados
const int pinStep = 4;
const int pinDir = 7;
const int pinEnable = 8;
// Creamos un objeto de tipo AccelStepper
AccelStepper stepper = AccelStepper(1, pinStep, pinDir);
SoftwareSerial BTSerial(10, 11); // Creamos un objeto SoftwareSerial para la comunicación Bluetooth
int rpm = 0;
const int dir = -1; // 1 para CW, -1 para CCW

void setup() {
  // Configuramos los pines
  pinMode(pinEnable, OUTPUT);
  digitalWrite(pinEnable, LOW); // Habilitamos el driver

  // Configuramos el objeto AccelStepper
  stepper.setMaxSpeed(2000); // Velocidad máxima en RPM
  BTSerial.begin(38400); // Iniciamos la comunicación Bluetooth
}

void loop() {
  byte c;
  if (BTSerial.available() > 0) {
    c = BTSerial.parseInt();
    if (c == 7)rpm = 0;
    else rpm = -50 + c * 100;
    stepper.setSpeed(dir * rpm * 3 );
  }
  stepper.runSpeed();
}