Walk on By

Description
In this assignment, we needed to build a crawler using the servo motor. The task proved to be quite tricky, especially since I was working with only one motor. My initial idea was to create some sort of stilts to mimic bipedal movements. However, after some rapid prototyping, this turned out to be difficult to do.
 
I came to the final solution after a few rounds of prototyping. At one point, I simply attached a wooden stick and observed the movement as I spun the servo motor back and forth. While doing this, I realized that the ends of the stick were hitting the same areas--the motor didn't move forward because there was no friction between the stick and the surface. Following this, I tried to attach a kneaded rubber eraser (typically used while drawing with charcoal or pencil) to one end. The purpose is twofold: to put more weight on one end and to create some traction with the surface. This approach seemed to work, and afterward I continued to experiment with different weight and length to optimize the crawler.
 
A video demo can be seen here: https://drive.google.com/file/d/0BzNIHWmnbWZ6TkYtY29HOW1PWTg/edit?usp=sharing
 
Components

1x 10k Ohm Resistor

1x Diode

1x Transistor

1x DC motor

1x Arduino Uno

1x Breadboard

1x Macbook Pro

1x Ouija board

1x Coin

1x Kneaded rubber eraser

Code

int servoPin = 7;      // Control pin for servo motor

int potPin   = 0;      // select the input pin for the potentiometer

int pulseWidth = 0;    // Amount to pulse the servo

long lastPulse = 0;    // the time in millisecs of the last pulse

int refreshTime = 20;  // the time in millisecs needed in between pulses

int val;               // variable used to store data from potentiometer

int minPulse = 500;   // minimum pulse width

void setup() {

  pinMode(servoPin, OUTPUT);  // Set servo pin as an output pin

  pulseWidth = minPulse;      // Set the motor position to the minimum

  Serial.begin(9600);         // connect to the serial port

  Serial.println("servo_serial_better ready");

}

void loop() {

  val = analogRead(potPin);    // read the value from the sensor, between 0 - 1024

  if (val > 0 && val <= 999 ) {

    pulseWidth = val*2 + minPulse;  // convert angle to microseconds

    Serial.print("moving servo to ");

    Serial.println(pulseWidth,DEC);

  }

  updateServo();   // update servo position

}

// called every loop(). 

void updateServo() {

  // pulse the servo again if the refresh time (20 ms) has passed:

  if (millis() - lastPulse >= refreshTime) {

    digitalWrite(servoPin, HIGH);   // Turn the motor on

    delayMicroseconds(pulseWidth);  // Length of the pulse sets the motor position

    digitalWrite(servoPin, LOW);    // Turn the motor off

    lastPulse = millis();           // save the time of the last pulse

  }

}