Assignment: Servo Motor: Actuation Assignment 2

Collaborators:

Description

In this assignment we are supposed to create a "crawler" - employing the rotational motion of the servo to provide linear motion of our artifact.

I missed the lab concerning servos because I was flying to Georgia for my brother's wedding. As such, I did not get access to a servo motor until the day before the assignment was due. Happily, Lora Oehlberg loaned me a second servo, allowing me to create an interesting project in a very short time.

I experimented briefly with different forms of linear motion, but in the end I chose to employ a set-up that resembles the example from the lab that I missed. I used the same general application of rotational force to move an object; however, I decided to make it more interesting by turning my altoids tin into something resembling a Mad Max-style tank.

Components Used

• 1 Arduino board
• 1 generic solderless breadboard
• 2 rubber bands to secure the Arduino board to the breadboard
• wires
• 1 1k Ohm resistor
• 1 diode
• 1 transistor
• 1 DC high-rotation, low-torque motor
• 2 AA batteries in a battery pack
• 2 wooden coffee stirrers
• electrical tape
• 1 pieces of string
• 2 servo motors
• 1 full Altoids can
• 1 potentiometer

Images and Video

Servo-Acutated Altoid Tank in motion

The beast

The guts

Ready to rock and roll

Arduino Code

/*
 * Servo with Potentiometer control
 * Theory and Practice of Tangible User Interfaces
 * October 11 2007
 */

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(7, 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");
 analogWrite(9, 100);
}

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(7, HIGH);   // Turn the motor on
 delayMicroseconds(pulseWidth);  // Length of the pulse sets the motor position
 digitalWrite(7, LOW);    // Turn the motor off
 lastPulse = millis();           // save the time of the last pulse
 }
}