Week 11 Machine Design

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This week we are going to atomate the mechanism that we made 2 weeks ago.

Softwares
  • Arduino IDE
    • Materials
  • 2x Wantai 42BYGHM809 Step motors
  • 2x Pololu DRV8834 driver carrier
  • Arduino UNO
  • Power supply
  • Jumpers and cables


    • MTM 2: ‘Maggie’ CNC Drawing Machine


    This is a groupal activity, so we devided all the activities, I will document what I've done but you can find the whole project here

    Programming the machine


    As we said before, we use an Arduino Uno and Pololu Driver to move a stepper motor. Before begin programming there are three things that we need to understand:

  • The stepper motor function by generating a temporal magnetic field when we polarize opposite coils, this make one step, to generate a continuous movement we need to polarize and depolarize consecutive coils with certain delays; this delay defines the rotary speed of the motor and they are inversely proportional, the longer the delay, the slower the speed and vice versa.

  • Pololu driver make two principal functions, first it acts as a H bridge, supplies power to the motor that the control circuit can’t supply; and second is responsible of making the sequential shift of the coils by the rhythm of an external clock and controls its direction, all this with PWM and digital commands respectively.

  • Arduino, in this case, defines the quantity of steps that we need the stepper make and the direction we want it to go.

    • Knowing this, to make the program practically we need to tell Arduino: “We need you to give 1000 steps on this direction, and for every step you have to put on 5V the step pin, wait, put on 0V, wait and repeat”

    On C++, it would be this:


    for (int p=0; p<1000; p++) {
        digitalWrite(pinStep, HIGH);
        delayMicroseconds(time);


        digitalWrite(pinStep, LOW);
        delayMicroseconds(timel);
    }



    This code lines will make that one motor give 1,000 steps. But we design our machine to move on 2 axis, so if we want to move both motors at the same time we have to tell the same to each motor, like this.


    for (int p=0; p<1000; p++) {
        digitalWrite(pinStepX, HIGH);
        digitalWrite(pinStepY, HIGH);
        delayMicroseconds(time);


        digitalWrite(pinStepX, LOW);
        digitalWrite(pinStepY, LOW);
        delayMicroseconds(timel);
    }



    This would do that both motors turn at the same time with the same speed, the direction is independent for each one.

    If we want a complete a program we need to set the IOs and the directions of movement, this code was our first sketch to test our machine and it will make a box with a diagonal in a very long method.


    //Variables and Pin Declaration

    int pinStepx = 11;
    int pinDirx = 12;
    int pinDiry = 10;
    int pinStepy = 9;
    int pinAdelante = 2;
    int pinAtras = 3;
    const int ledPin = LED_BUILTIN;

    void setup() {
    //Set IO
    pinMode(pinStepx, OUTPUT);
    pinMode(pinDirx, OUTPUT);
    pinMode(pinStepy, OUTPUT);
    pinMode(pinDiry, OUTPUT);

    pinMode(pinAdelante, INPUT_PULLUP);
    pinMode(pinAtras, INPUT_PULLUP);
    pinMode(ledPin, OUTPUT);

    //Initializing
    digitalWrite(pinStepx, LOW);
    digitalWrite(pinDirx, LOW); //Low get closer to motor, High get farther
    digitalWrite(pinStepy, LOW);
    digitalWrite(pinDiry, HIGH); //Low get farther from the motor, High get closer
    digitalWrite(ledPin,LOW);
    delayMicroseconds(500);

    //Setting Delay
    int vel = 500;

    for(int p=0;p<10000;p++){ //Right
    digitalWrite(pinStepy, HIGH);
    delayMicroseconds(vel);
    digitalWrite(pinStepy, LOW);
    delayMicroseconds(vel);
    }

    for(int p=0;p<10000;p++){ //Down
    digitalWrite(pinStepx, HIGH);
    delayMicroseconds(vel);
    digitalWrite(pinStepx, LOW)
    ; delayMicroseconds(vel);
    }

    digitalWrite(pinDirx, HIGH);
    digitalWrite(pinDiry, LOW);








    for(int p=0;p<10000;p++){ //Left
    digitalWrite(pinStepy, HIGH);
    delayMicroseconds(vel);

    digitalWrite(pinStepy, LOW);
    delayMicroseconds(vel);
    }

    for(int p=0;p<10000;p++){ //Arriba
    digitalWrite(pinStepx, HIGH);
    delayMicroseconds(vel);

    digitalWrite(pinStepx, LOW);
    delayMicroseconds(vel);
    }

    digitalWrite(pinDirx, LOW); //Down-Left
    digitalWrite(pinDiry, HIGH);

    for(int p=0;p<10000;p++){
    digitalWrite(pinStepx, HIGH);
    digitalWrite(pinStepy, HIGH);
    delayMicroseconds(vel);

    digitalWrite(pinStepx, LOW);
    digitalWrite(pinStepy, LOW);
    delayMicroseconds(vel);
    }

    digitalWrite(pinDirx, HIGH);

    for(int p=0;p<10000;p++){ //Up
    digitalWrite(pinStepx, HIGH);
    delayMicroseconds(vel);

    digitalWrite(pinStepx, LOW);
    delayMicroseconds(vel);
    }

    digitalWrite(pinDirx, LOW); //Down-Right
    digitalWrite(pinDiry, LOW);

    for(int p=0;p<10000;p++){
    digitalWrite(pinStepx, HIGH);
    digitalWrite(pinStepy, HIGH);
    delayMicroseconds(vel);

    digitalWrite(pinStepx, LOW);
    digitalWrite(pinStepy, LOW);
    delayMicroseconds(vel);
    }

    digitalWrite(ledPin, HIGH); //Turn on LED when finish

    }



    A very large code, and it will be larger if we want the machine to execute more movements, so we realized that we can sintetize it by making a function with the code that is repetitive, and this is the "for cycle".

    Determining Ratios


    But first we need to measure some parameters, like the relation of the rotation and the straight line distance, and the relation of the delay with the speed.

    Once we had the X and Y axis assembled and the motors connected, we made the program to draw horizontal and vertical lines using first milliseconds and measuring how many centimeters the motors ran in that specific time. Using that information, we were able to define a formula to make the motors run changing the distance instead of changing the time.

    Thanks to this calculation we could define that the amount of steps it will be equal to the stright line distance we want to draw on milimeters multiplied by 250
    steps = distance * 250

    And the delay will be a factor of 15,000,000/(1200*6.25) divided by the linear speed on milimeters per seconds
    delay = 15000000/(1200 * 6.25 * linearSpeed)

    Code synthesis


    //Declaration

    int pinStepx = 11;
    int pinDirx = 12;
    int pinDiry = 10;
    int pinStepy = 9;
    const int ledPin = LED_BUILTIN;

    void setup() {
    //Set IO
    pinMode(pinStepx, OUTPUT);
    pinMode(pinDirx, OUTPUT);
    pinMode(pinStepy, OUTPUT);
    pinMode(pinDiry, OUTPUT);
    pinMode(ledPin, OUTPUT);

    //Initialize
    digitalWrite(pinStepx, LOW);
    digitalWrite(pinDirx, LOW); //Low hacia el motor, High fuera del motor
    digitalWrite(pinStepy, LOW);
    digitalWrite(pinDiry, HIGH); //Low fuera del motor, High hacia el motor
    digitalWrite(ledPin,LOW);
    delayMicroseconds(500);

    //Instructions
    line(40, String('l'), 4.5);
    line(20, String('d'), 4.5);
    line(40, String('r'), 4.5);
    line(20, String('d'), 4.5);
    line(40, String('l'), 4.5);
    diag(40, 40, String("ul"), 4.5);
    diag(40, 40, String("dl"), 4.5);

    }

    void loop(){

    }

    //Functions
    void line(int dist, String dir, int velmot){
    //10,000 steps are 25 turns and 4cm

    int vel = 15000000/(1200*6.25*velmot);
    int steps = dist*250;
    int pin;

    if (dir == "u"){
    digitalWrite(pinDirx, HIGH); //Up
    pin = pinStepx;
    } else if (dir == "d"){
    digitalWrite(pinDirx, LOW); //Down
    pin = pinStepx;
    } else if (dir == "r"){
    digitalWrite(pinDiry, HIGH); //Right
    pin = pinStepy;
    } else if (dir == "l"){
    digitalWrite(pinDiry, LOW); //Left
    pin = pinStepy;
    }


    for(int p=0;p digitalWrite(pin, HIGH);
    delayMicroseconds(vel);

    digitalWrite(pin, LOW);
    delayMicroseconds(vel); }

    digitalWrite(ledPin, HIGH);
    delay(500);
    digitalWrite(ledPin, LOW);
    }

    void diag(int distx, int disty, String dir, int velmot){
    //10,000 steps son 25 vueltas son 4cm

    //int teta = atan(disty/distx);
    //int velmotx = cos(teta)*velmot;
    int velx = 15000000/(1200*6.25*velmot);

    //int velmoty = cos(teta)*velmot;
    //int vely = 150000000/(1200*6.25*velmoty);

    int stepsx = distx*250;
    int stepsy = disty*250;
    int pin;

    if (dir == "ur"){
    digitalWrite(pinDirx, HIGH); //Up
    digitalWrite(pinDiry, HIGH); //Right
    } else if (dir == "ul"){
    digitalWrite(pinDirx, HIGH); //Up
    digitalWrite(pinDiry, LOW); //Left
    } else if (dir == "dr"){
    digitalWrite(pinDirx, LOW); //Down
    digitalWrite(pinDiry, HIGH); //Right
    } else if (dir == "dl"){
    digitalWrite(pinDirx, LOW); //Down
    digitalWrite(pinDiry, LOW); //Left
    }

    for(int p=0;p digitalWrite(pinStepx, HIGH);
    digitalWrite(pinStepy, HIGH);
    delayMicroseconds(velx);

    digitalWrite(pinStepx, LOW);
    digitalWrite(pinStepy, LOW);
    delayMicroseconds(velx);
    }

    digitalWrite(ledPin, HIGH);
    delay(500);
    digitalWrite(ledPin, LOW);
    }













    This code works as a "Baby G-Code" because we only need to specify, for example, in the command line(distance, direction, speed) and in the command diag(distance X, distance Y, direction, speed). It still has some delimitation, it can't draw diagonals lines with an angle different from 45°, and can't draw curves.

    Results

    Here is the sequence of the test that we made





    Here is a video of what does the last program that we made!!!



    Week 11 - Machine Design from Ivan Lopez on Vimeo.