jkufro Demo 3: Responsive Cars

Justin Kufro

Partner: Oshada Gunasekara

These responsive cars are made to communicate through sensing the world through limit switches. One car moves only when its limit switch is open, while the other moves only when its limit switch is closed. They are intended to be placed in front of each other so that they seem to chase one another around.

One of the subgoals for this demo was having simplicity of design. Both cars use just two laser-cut pieces of 6mm plywood, a DC motor, and a limit switch. The tradeoff to this is that the cars tend to turn in the rightward direction instead of driving straight. Wires tethered to a computer and wall outlet just amplify the issue further.

Video

Files

jkufro-demo3-sldw

Code

const int MOTOR_PIN_1 = 5;
const int MOTOR_PIN_2 = 6;
const int LIMIT_SWITCH_PIN = 13;

void setup() {
  // put your setup code here, to run once:
  pinMode(MOTOR_PIN_1, OUTPUT);
  pinMode(MOTOR_PIN_2, OUTPUT);
  pinMode(LIMIT_SWITCH_PIN, INPUT);
}

// https://courses.ideate.cmu.edu/16-223/f2018/text/lib/WheelDrive.html
void set_motor_pwm(int pwm, int MOTOR_PIN_1, int MOTOR_PIN_2)
{
  if (pwm < 0) {  // reverse speeds
    analogWrite(MOTOR_PIN_1, -pwm);
    digitalWrite(MOTOR_PIN_2, LOW);

  } else { // stop or forward
    digitalWrite(MOTOR_PIN_1, LOW);
    analogWrite(MOTOR_PIN_2, pwm);
  }
}

// https://courses.ideate.cmu.edu/16-223/f2018/text/lib/WheelDrive.html
void set_motor_currents(int pwm_A, int pwm_B)
{
  set_motor_pwm(pwm_A, MOTOR_PIN_1, MOTOR_PIN_2);
  set_motor_pwm(pwm_B, MOTOR_PIN_1, MOTOR_PIN_2);
}

// https://courses.ideate.cmu.edu/16-223/f2018/text/lib/WheelDrive.html
void spin_and_wait(int pwm_A, int pwm_B, int duration)
{
  set_motor_currents(pwm_A, pwm_B);
  delay(duration);
}

void loop() {
  int value = digitalRead(LIMIT_SWITCH_PIN);
  if (value == 0) {
    spin_and_wait(255,255,2000);
  } else {
    spin_and_wait(0,0,50);
  }
}