Lab 7 - Servo Crawler

Submitted by seanchen on Tue, 03/19/2013 - 22:55


I ended up having a excavator-like crawler because I need the servo to be in the middle. Before that, I tried numerous types of crawler: servo on the side, two clips on each side that were tied on a popsicle,    but they all failed because they kept going in circles. This one more or less still does, because it's hard to keep the clip  straight. But sometimes with good control it can go straight forward pretty fast. Since the servo is hanging in the front, I added the batteries to balance the weight. Rubber on the clip is used to increase friction.



1 x Arduino UNO Board
1 x Potentiometer
1 x Servo motor
clip, ruler, rubber bands, balloon, batteries as weight, 




 * Servo with Potentiometer control
 * Theory and Practice of Tangible User Interfaces
 * October 11 2007
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 ");
  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
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