Week 4: Driving something bigger

Arduino Motor

I have started putting these on Github so you can also follow along.

In Weeks 2, and 3 we were driving LEDs directly from the Arduino, While the Arduino can drive a LED directly from a pin, if you want to power something that draws more power like a motor, you will need to provide more power than the Arduino can provide; one way to control larger loads is to use a Transistor.

For this circuit we are going to use a 2N2222A transistor, these little components come in at about 20p each in low quantity.

2N2222A
2N2222A
/*     -----------------------------------------------------------
 *     |  Arduino Experimentation Kit Example Code               |
 *     |  CIRC-03 .: Spin Motor Spin :. (Transistor and Motor)   |
 *     -----------------------------------------------------------
 * 
 * The Arduinos pins are great for driving LEDs however if you hook 
 * up something that requires more power you will quickly break them.
 * To control bigger items we need the help of a transistor. 
 * Here we will use a transistor to control a small toy motor
 * 
 * http://tinyurl.com/d4wht7
 *
 */

int motorPin = 9;  // define the pin the motor is connected to
                   // (if you use pin 9,10,11 or 3you can also control speed)

/*
 * setup() - this function runs once when you turn your Arduino on
 * We set the motors pin to be an output (turning the pin high (+5v) or low (ground) (-))
 * rather than an input (checking whether a pin is high or low)
 */
void setup()
{
 pinMode(motorPin, OUTPUT); 
}


/*
 * loop() - this function will start after setup finishes and then repeat
 * we call a function called motorOnThenOff()
 */

void loop()                     // run over and over again
{
 motorOnThenOff();
 //motorOnThenOffWithSpeed();
 //motorAcceleration();
}

/*
 * motorOnThenOff() - turns motor on then off 
 * (notice this code is identical to the code we used for
 * the blinking LED)
 */
void motorOnThenOff(){
  int onTime = 2500;  //the number of milliseconds for the motor to turn on for
  int offTime = 1000; //the number of milliseconds for the motor to turn off for
  
  digitalWrite(motorPin, HIGH); // turns the motor On
  delay(onTime);                // waits for onTime milliseconds
  digitalWrite(motorPin, LOW);  // turns the motor Off
  delay(offTime);               // waits for offTime milliseconds
}

/*
 * motorOnThenOffWithSpeed() - turns motor on then off but uses speed values as well 
 * (notice this code is identical to the code we used for
 * the blinking LED)
 */
void motorOnThenOffWithSpeed(){
  
  int onSpeed = 200;  // a number between 0 (stopped) and 255 (full speed) 
  int onTime = 2500;  //the number of milliseconds for the motor to turn on for
  
  int offSpeed = 50;  // a number between 0 (stopped) and 255 (full speed) 
  int offTime = 1000; //the number of milliseconds for the motor to turn off for
  
  analogWrite(motorPin, onSpeed);   // turns the motor On
  delay(onTime);                    // waits for onTime milliseconds
  analogWrite(motorPin, offSpeed);  // turns the motor Off
  delay(offTime);                   // waits for offTime milliseconds
}

/*
 * motorAcceleration() - accelerates the motor to full speed then
 * back down to zero
*/
void motorAcceleration(){
  int delayTime = 50; //milliseconds between each speed step
  
  //Accelerates the motor
  for(int i = 0; i < 256; i++){ //goes through each speed from 0 to 255 analogWrite(motorPin, i); //sets the new speed delay(delayTime); // waits for delayTime milliseconds } //Decelerates the motor for(int i = 255; i >= 0; i--){ //goes through each speed from 255 to 0
    analogWrite(motorPin, i);   //sets the new speed
    delay(delayTime);           // waits for delayTime milliseconds
  }
}

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