Description:

A few choices that I made:
– I used a bundle of knives to counterbalance the weight of the fork and the motor. At first I was worried that they would make it too heavy altogether, but it ended up being okay.
– I used tape to fix the joints of the frame thingy (which was just a novelty item that my roommate brought home from his IBM museum visit).
– I chose a fork as an arm, first because I thought that the pointier side of the fork would stick in the carpet and effectively move it, while the other side (with the tine points facing up) would slide along the floor. Instead, when the tines were facing down, they kind of skipped along the floor and didn’t effective move the crawler, so it ended up crawling in the other direction.

I left the code unchanged from the example, and just used the pot to manually control it.

Components Used:

• 1 Arduino
• 1 Servomotor
• 1 Breadboard
• 1 pot
• 2 pipe cleaners (to lash the fork to the motor)
• lots of masking tape
• 4 knives
• 1 fork

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
 }
}

VIDEO: lab07