Assignment: DC Motor: Actuation Assignment 1

Collaborators:

Description

I wanted to make something active and interesting using the motor. I decided to try to actuate a cheap spider ring. I tried using cork, using rubber bands, using posterboard, but nothing worked quite right. The problem was that the motor did not have sufficient torque, so by the time I cranked it up high enough to overcome rotational inertia and get the spiders moving, they would end up spinning wildly then getting tangled up in the motor.

In the end, I realized that my best option was not to use the full rotational functionality of the motor, but to allow partial rotation and gravity to counteract each other and provide a sort of jerky motion to the system. In order to do this, I needed a relatively large inertial problem for the motor and the proper code. I settled on a piece of cork (to transfer most of the rotational force of the motor) attached to a coffee stirrer, that acted as the rail on which I hung my spiders. After that, it was just a matter of finding the proper amount of motor output to use and the delays to incorporate.

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
• 1 piece of cork
• 1 wooden coffee stirrer
• 9 plastic spider rings
• 1 pieces of string, disassembled into 7 pieces of thread
• 1 YamaMotoYama tea bag string, whole
• hot glue

Images and Video

DC Motor connection (software controls actuation, so there is no input device)

An overview of the setup

A closeup of the motor setup.

Spider-ring puppet show - DC Motor in action

A video of the system in action.

Arduino Code

/*
 * Make a DC motor sporadically rotate an object
 * with non-trivial rotation inertia. Designed
 * for an array of plastic spiders hanging from
 * string for Lab assignment 6.
 *
 * Seth Horrigan
 */

int motorPin = 9; // select the pin for the Motor
void setup() {
 Serial.begin(9600);
}
void loop() {
 //Write between 75 and 125 to DC Motor
 analogWrite(motorPin, 100);
 //Turn the motor on for 100-250 ms
 delay(150 + random(200));
 analogWrite(motorPin, 0);
 //Turn the motor off for 100-2600 ms
 delay(100 + random(2500));
}