Easy Driver With Arduino

 

Part I              (Maximum Stepper Speed)

Go to Part II   (Adjust max Stepper Current)

Go to Part III (Sleep an Enable)

 

 

 

Click Here to see and download the design of a PCB implementing this circuit.

 

An important thing to knwo about your stepper, is the maximum speed at witch it can be driven.
To know this, you can follow this LINK;

you need to knwo the specs of your stepper.
For my stepper:

  Voltage:                                  12v
  Inductance:                             46+-20% mH           then i take 50
  Steps per revolution:              Step Angle = 1.8º     360 / 1.8 = 200 Steps/rev
  Current:                                  0.33 A                       i take 135 mA because with easy
                                                                                   driver you can adjust the maximun current
                                                                                   with the potenciometer
                                                                                   (i will explain this in a future post)

then following the calculs from the previous link:

  T = 50 * 0.135 * 2 / 12 = 1.125 ms for a single Step

The default configuration of EasyDriver is eighth stepping then:

  T = 1.125 / 8 = 0.140 ms = 140 us for a single Step

given this we take a prescaler of 128 for the Timer2 (see coments in the code)

  128 / 16000000 = 0.000008 s-1 = 8 us-1         ( the frequency of the processor in the
                                                                              Arduino Uno is 16 MHz)

  Timer2 actulizes its counter every 8 us then, 140 / 8 = 17.5

then we have to program the counter for the Timer2 to 18 ( 18 = ceil(17.5) ), because of that we have a success of Timer2 every 18 * 8us = 144 us

and the speed for our stepper will be: 144 us * 1600 Steps/Revolution = 0.2304 s/Revolution

that is 1 / 0.2304 = 4.34 Revolutions / s , wich is an aproximation to the real speed, because there is an extra delay between steps introduced by the code itself  ( maybe 20 us extra delay ).


To see this working copy the following code to Arduino IDE, set the proper value for  this variables
      microSteping
      stepsPerRev
      l
      v
      iMax
 and run it.

This program also implements acceleration-desacceleration. You can change the amount of acceleration, changing the value of  'accelDuring' variable ( for example it accelerates during 10 steps the run at constant speed and finaly it desaccelerates during 10 steps ).
If you don't want acceleration set it to 0 ( accepted values are 0 - 255 ).

//http://www.daycounter.com/Calculators/Stepper-Motor-Calculator.phtml
//Rev/sec = V/(L*2*Imax)/(steps/rev)  (Imax en A, L en mili Herns) p.e. 12/(46*2*0.33)/200
//T = L*Imax*2/V (T miliSegons/step)
  
  #define DIR_PIN 7
  #define STEP_PIN 6
  #define sbi(sfr,bit)  ( sfr |=   _BV(bit)  )         // a l'antiga manera. cbi() i sbi() son funcions obsoletes
  #define cbi(sfr,bit)  ( sfr &= ~(_BV(bit)) )  
  //  MS1  MS2  Resolution
  //  L    L    00 Full step (2 phase)
  //  H    L    10 Half step
  //  L    H    01 Quarter step
  //  H    H    11 Eighth step
  //
  // per defecte a la easy driver MS1 = MS2 = HIGH
  
  float microStepping = 8;                             // Valor establert a la easyDriver ( MS1, MS2 )
  long stepsPerRev = 200;                              // característica del motor
  float l = 50;                                        // = 46 +- 20% (el pitjor dels casos es 55.2) característica del motor
  float v = 12;                                        // característica del motor
  float iMax = 0.135;                                  // mesurat amb el tester (cal dividir el resultat per 2 (hi ha 2 bobines))
                                                       // amb la EasyDriver podem controlar iMax abm el potenciòmetre
                                                       
  float ocr2a;                                         // valor de OCR2A ( que depèn de la velocitat màxima del Stepper )
  int ocr2aIni;                                        // valor inicial de OCR2A donada l'acceleració
  
  int accelDuring = 10;                                // Accelera i desaccelera durant 10 Steps
                                                       
  int downCounter = accelDuring;                       // el nombre d'Steps que falten fins acabar la desacceleració
  int upCounter = accelDuring;                         // el nombre d'Steps que falten fins acabar l'acceleració
  int accelDelta;                                      // valor en que varia OCR2A durant l'acceleració 
                                                       // ( p.e. si ha de pasar de 255 a 19 en 10 steps decremeta de 23 en 23 i começa a 249 )
                                                       
  long stepsLeft = 0;                                  // nombre d'Steps que manque per acabar
  boolean running = false;                             // motor is running?
  
  
  
  void setup() {
    unsigned int usDelay;                              // temps d'espera entre Steps en us
      
    Serial.begin(115200);
    pinMode(DIR_PIN, OUTPUT);
    pinMode(STEP_PIN, OUTPUT);
  
    usDelay = l * 2000 * iMax / v / microStepping;     // temps d'espera entre steps en microsegons  ( T= L*Imax*2/V (T miliSegons/step) )
    ocr2a = ceil((float)usDelay / 8.0);                // l'enter mes proper donat l'interval del Timer2 ( 8 us )
  
    Serial.println(ocr2a);
  
    if(accelDuring > 0){
      accelDelta = (255 - int(ocr2a) ) / accelDuring;  // OCR2A pasarà del enter mes proper a 255 fins a ocr2a
                                                       // el valor que hem calculat per la velocitat màxima
    Serial.println(accelDelta);
      
      if(accelDelta<=0){
        if(ocr2a < 255){                               // la durada de l'acceleració no pot ser tan gran com esperem
          accelDelta =1;
          ocr2aIni = 255;
          accelDuring = 255 - ocr2a;                   // durada màxima de l'acceleració permesa
          
        }else{                                         // ocr2a = 255, no hi pot haver acceleració
          accelDelta = 0;
          accelDuring = 0;
          ocr2aIni = ocr2a;
        }
        
      }else                                            // acceleració segons la definició
        ocr2aIni = ocr2a + accelDelta * accelDuring;   // calcula el OCR2A inicial donada l'acceleració
        
    }else                                              // no hi ha acceleració
      ocr2aIni = ocr2a;
  
    Serial.println(ocr2aIni);
  
    setTimer2(ocr2aIni);
  
    Serial.print("Inter Step Delay: ");
    Serial.print(usDelay);
    Serial.println(" us");
    Serial.print("Max Speed: ");
    Serial.print( 60000000.0 / ((float)stepsPerRev * microStepping * (usDelay)) );
    Serial.println(" RPM");
    Serial.print("Inter Step Delay programat a Timer2: ");
    Serial.println((int( ceil( (float)usDelay / 8.0 ) ))*8);
    Serial.print("Max Speed Real: ");
    Serial.print( 60000000.0 / ((float)stepsPerRev * microStepping * ((int( ceil( (float)usDelay / 8.0 ) ))*8)) );
  }//// 
  
  
  
  long nVoltes = 1;
  long nSteps = nVoltes * stepsPerRev * microStepping;
  

  void loop(){
    if(!running){
 delay(1000);
      driveStepper(nSteps);
      nSteps = -nSteps;
    }
  }////
  
  
  
  
  
  
  void driveStepper(long lnSteps){
    int dir = (lnSteps > 0)? HIGH:LOW;
    digitalWrite(DIR_PIN,dir);
  
    lnSteps = abs(lnSteps);
  
    OCR2A = ocr2aIni;                // reinicialitza el contador (permet acceleració)
    upCounter = accelDuring;
    downCounter = accelDuring;
    running = true;
    stepsLeft = lnSteps;
  }////
  
  
  
  void setTimer2(int lusDelay) {
  
    //http://arduino.cc/en/Tutorial/SecretsOfArduinoPWM
    // The ATmega328P has three timers known as Timer 0, Timer 1, and Timer 2
    // Each timer has two output compare registers 
    // Each of the timers has a prescaler that generates the timer clock by dividing
    //         the system clock by a prescale factor such as 1, 8, 64, 256, or 1024
    //         Note that Timer 2 has a different set of prescale values from the other timers
    // The Arduino has a system clock of 16MHz and the timer clock frequency will be
    //         the system clock frequency divided by the prescale factor
    // The timers can also generate interrupts on overflow and/or match against either output compare register
    //
    // TCCRnA and TCCRnB. The Timer/Counter Control Registers hold the main control bits
    //            for the timer. (Note that TCCRnA and TCCRnB do not correspond to the outputs A and B.) 
    // TCCRnA and TCCRnB hold several groups of bits: 
    //     Waveform Generation Mode bits (WGM): these control the overall mode of the timer.
    //         (These bits are split between TCCRnA and TCCRnB.) 
    //     Clock Select bits (CS): these control the clock prescaler 
    //     Compare Match Output A Mode bits (COMnA): these enable/disable/invert output A 
    //     Compare Match Output B Mode bits (COMnB): these enable/disable/invert output B 
    //
    // OCRnA and OCRnB. The Output Compare Registers set the levels at which outputs A and B will be affected
    //
    // TIMSK2 – Timer2 Interrupt Mask Register
    //     OCIE2B: Timer2 Output Compare Match B Interrupt Enable
    //     OCIE2A: Timer2 Output Compare Match A Interrupt Enable
    //     TOIE2:  Timer2 Overflow Interrupt Enable
    //
    // Timer 1 is a 16-bit timer and has additional modes. Timer 2 has different prescaler values
    //
    // The Arduino uses Timer 0 internally for the millis() and delay() functions
    // OC0A pin  6   OC0B pin  5
    // OC1A pin  9   OC1B pin 10
    // OC2A pin 11   OC2B pin  3 
  
    cli();                           // plana 10. Bit 7 Clear interrupts
  
    cbi(TCCR2A, COM2A0 );            // plana 158. Table 17-2. Normal port operation, OC0A disconnected. 
    cbi(TCCR2A, COM2A1 );            // 00 deconecta el pin A del timer2
  
    cbi(TCCR2A, WGM20  );            // TCCR2A Regitre A de control del timer 2
    sbi(TCCR2A, WGM21  );       // plana 160 i 149. Clear Timer on Compare
    cbi(TCCR2B, WGM22  );            // WGM2 = 010 ==> mode of operation Clear Timer on Compare (CTC)
                                     // The counter value TCNT2 increases until TCNT2 == OCR2A, 
                                     // and then counter (TCNT2) is cleared
                                     // repeteix el cilce 0 --> valor ( valor clocks )
  
    sbi(TCCR2B, CS22   );            // TCCR2B Regitre B de control del timer 2
    cbi(TCCR2B, CS21   );       // Plana 162
    sbi(TCCR2B, CS20   );            // CS2 = 101 prescaler = 128 ==> 128/16.000.000 = 0.000008 s-1 = 8us-1
                                     // màxim temps que es pot contar = 8 * 255 = 2040 us
  
    sbi(TIMSK2, OCIE2A  );           // Timer2 Output Compare Match A Interrupt Enable. plana 163
  
    cbi(ASSR, AS2);              // AS2 = 0 clocked from the I/O clock
                                     // plana 164. Asynchronous Status Register
                                     // When AS2 is written to zero, Timer/Counter2 is clocked from the I/O clock, clkI/O.
                                     // When AS2 is written to one, Timer/Counter2 is clocked from a crystal Oscillator
                                     // connected to the Timer Oscillator 1 (TOSC1) pin.    
  
    OCR2A = lusDelay;                //  si p.e. OCR2A = 21 --> 21*0.000008 = 168us-1  . cridem la funcio un cop cada 168 us. plana 162
  
    TCNT2 = 0;                       // reset Timer2 counter
  
    sei();                           // Enable Interrupts
  }////
  
  
  
  void stopTimer2() {
    cbi(TIMSK2, OCIE2A  );           // Timer2 Output Compare Match A Interrupt Disable. plana 163
  }////
  
  
  
                                     
  ISR(TIMER2_COMPA_vect) {           // Timer2 Output Compare Match A Interrupt
                                     // definició dels vectors a Arduino\hardware\tools\avr\avr\include\iom328p.h     
                                     // definitions for ATmega328P
    if(stepsLeft > 0){
      if(stepsLeft == downCounter){  // ha de desaccelerar
        downCounter--;
        OCR2A += accelDelta;         // incrementa el temps entre Steps en CS22:0 us (el proper Step es produirà 8 us mes tard)
      }
      else if(upCounter >0){         // ha d'accelerar
        upCounter--;
        OCR2A -= accelDelta;         // decrementa el temps entre Steps en CS22:0 us (el proper Step es produirà 8 us abans)
      }
      digitalWrite(STEP_PIN, HIGH);  // envia el pols a la EasyDriver per avançar 1 Step
      digitalWrite(STEP_PIN, LOW);   // A low-to-high transition on the STEP input sequences the translator 
                                     // and advances the motor one increment.       
                                     // Minimum STEP Pulse Width 1.0 μs (plana 7 de 'A3967.pdf')
                                     // la intruccio NOP triga 1 Clock ( 0,0625 us = 62.5 ns ) per tant
                                     // la instrucció digitalWrite ha de trigar més de 16 Clocks
                                     // mirar el codi a 'wiring_digital.c'
                                     // segons els forums 'digitalWrite()' sembla trigar entre 6 i 9 us
                                     // depenent de si el port es PWM o no
                                     // http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1230286016
      stepsLeft--;
    }
    else                             // para el motor
      running = false;
  }////
  
  

Trheading a function with parameters in Processing

In Processing if you want that a function is executed in a diferent thread, you have just to use the following command:

  thread("myFunc");       // this command creates a new thread and executes myFunc in that thread

  void myFunc(){ ..... }

  The restriction is that 'myFunc' must be void, with no parameters and it could not be declared in a subclass in the sketch (it must be a public function in the pApplet class).

With the following code you could thread a public function inside any class, with any number of parameters:

public void thread(final Metode metode, final Object... parametres) {                 // és el mateix que el thread de Processing, però amb paràmetres
  Thread later = new Thread() {  public void run() {  metode.run(parametres);  }  };  // i a més el Mètode pot pertanyer a qualsevol Clase
  later.start();
}

to use this alternative version of 'thread', you have to do the following:

 Metode resend = new Metode(myObject, "myFunc", byte.class, int.class);
 thread( resend, toSend, mill );

where 'myObject'  is an object of the cass that contains myFunc  (if the function is in in the same class were you declare 'resend' you can use 'this' instead of 'myObject'):

  class myClass{
    .....
    public void myFunc(byte toSend, int mill){ ..... }
    .....
  }

  myClass myObject = new myClass();

you can find 'Metode' class in this post: Metode Class