Description

Create a crawler using the servo motor. 

I used some cardboard to make the crawler arm. I cut a chunk of the middle of the arm out so that when it returns to the first position it can swing up without pushing the crawler backwards. I also added a weight to the end of the arm to make sure it extends fully and pushes the crawler forward.

Components Used

1 servo motor

cardboard box for base

cardboard scraps for the arm

magnet for the weight

Arduino Code

/*
 * Servo Control Serial
 * modified for TUI October 2007
 * Servo Serial Better
 * -------------------
 *
 * Created 18 October 2006
 * copyleft 2006 Tod E. Kurt <tod@todbot.com>
 * http://todbot.com/
 *
 * adapted from "http://itp.nyu.edu/physcomp/Labs/Servo"
 */

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

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 serial port

int minPulse = 500;   // minimum pulse width
int maxPulse = 2250;  // maximum 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 control program ready");
}

void loop() {
  val = Serial.read();      // read the serial port
  if (val >= '1' && val <= '9' ) {
    val = val - '0';        // convert val from character variable to number variable
    val = val - 1;          // make val go from 0-8
    pulseWidth = (val * (maxPulse-minPulse) / 8) + minPulse;  // convert val to microseconds
    Serial.print("Moving servo to position ");
    Serial.println(pulseWidth,DEC);
  }
  updateServo();   // update servo position
}

// called every loop(). 
// uses global variables servoPi, pulsewidth, lastPulse, & refreshTime
void updateServo() {
  // pulse the servo again if rhe refresh time (20 ms) have 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
  }
}

Items (picture and video)

crawler

link to video