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Arduino Projects Book - Project 10: Zoetrope

OVERVIEW:

In the past when people had not yet invented the television, movie theaters used a very long ribbon of static images and rolled it very fast to create an illusion of a video clip. The device that helped them make movies using that method is called Zoetrope. Today, I’m gonna use the Arduino and a DC motor to simulate how Zoetrope works.

L293D H-BRIDGED INTEGRATED CIRCUIT:

The key to controlling the DC motor in this project is the H-bridge IC. It’s called integrated circuit because there are many tiny circuits inside it, sometimes identical ones. IC makes the circuit tidier and helps the wiring much easier. For instance, in this project, we can have the full control of the DC motor using this IC alone, whereas we had to use a MOSFET and a diode to operate the motor in the previous project.

l293dne

There is a variety of ICs, so understanding the structure of the one we want to use is crucial. In fact, we must look at the datasheet of an IC to know what exactly it does. Here is important information I snipped from the sheet

ic-pins

The figure on the left shows the pin structure of the 20-pin IC; I don’t use it, so I just ignore it. I’m using the 16-pin IC with 8 pins on each side. This structure can be divided into 4 identical parts. They are identical and have the same functions: input, output, and ground.

For more information, see the IC data sheet.

PULSE-WIDTH MODULATION (PWM):

Pulse-width modulation is to modulate the width of the pulse. We can lengthen or shorten the HIGH duration of a signal without changing its frequency. For full information about PWM and analogWrite, please visit Arduino’s official tutorial.

PARTS:

arduino-uno

breadboard

parts

CIRCUIT:

As usual, here is the schematic:

schematic

And this is the virtual layout of my breadboard:

breadboard-layout

As always, they are available on my GitHub. Finally, this is how I wired my circuit:

build

CODE:

See below for my code, or view it on my GitHub.

/**
 * Project Name: Arduino Projects Book - Project 10: Zoetrope
 *
 * File Name: zoetrope.ino
 *
 * Description: Controls the speed and the direction of the DC motor using
 * two switches and a potentiometer.
 *
 * Author: Phi Luu
 * Location: Portland, Oregon, United States
 * Created: August 21, 2016
 * Updated: June 22, 2017
 */

// Required hardware I/O connections
const byte POT_PIN              = A0; // connect potentiometer to A0
const byte IC_INPUT_1           = 3;  // connect IC Input1 to ~3
const byte IC_INPUT_2           = 2;  // connect IC Input2 to 2
const byte IC_ENABLE_1          = 9;  // connect IC Enable1 t ~9
const byte DIRECTION_SWITCH_PIN = 4;  // connect direction switch to 4
const byte STATE_SWITCH_PIN     = 5;  // connect state switch to ~5

// Global variables
byte state_switch_val          = 0;   // state switch
byte direction_switch_val      = 0;   // direction switch
byte prev_state_switch_val     = 0;   // previous state switch
byte prev_direction_switch_val = 0;   // previous direction switch
byte motor_is_enabled          = 0;   // whether the motor is on/off
byte motor_direction           = 0;   // motor direction
unsigned short motor_speed     = 0;

void setup() {
    pinMode(DIRECTION_SWITCH_PIN, INPUT);
    pinMode(STATE_SWITCH_PIN,     INPUT);
    pinMode(IC_INPUT_1,           OUTPUT);
    pinMode(IC_INPUT_2,           OUTPUT);
    pinMode(IC_ENABLE_1,          OUTPUT);
}

void loop() {
    state_switch_val = digitalRead(STATE_SWITCH_PIN);
    delay(1);
    direction_switch_val = digitalRead(DIRECTION_SWITCH_PIN);
    motor_speed          = analogRead(POT_PIN) / 4;

    // process the on/off state of the motor from the state switch
    if (state_switch_val != prev_state_switch_val) {
        if (state_switch_val) {
            motor_is_enabled = !motor_is_enabled;
        }
    }

    // process the direction of the motor from the direction switch
    if (direction_switch_val != prev_direction_switch_val) {
        if (direction_switch_val) {
            motor_direction = !motor_direction;
        }
    }

    // control the direction of the motor using the IC
    if (motor_direction) {
        digitalWrite(IC_INPUT_1, LOW);
        digitalWrite(IC_INPUT_2, HIGH);
    } else {
        digitalWrite(IC_INPUT_1, HIGH);
        digitalWrite(IC_INPUT_2, LOW);
    }

    // control the on/off state of the motor using PWM
    if (motor_is_enabled) {
        analogWrite(IC_ENABLE_1, motor_speed);
    } else {
        analogWrite(IC_ENABLE_1, 0);
    }

    // prep for next inputs
    prev_state_switch_val     = state_switch_val;
    prev_direction_switch_val = direction_switch_val;
}

USING:

There should have been a colorful pinwheel with a black ribbon standing on it and a ribbon of static images inside, but I messed up the ribbons. So, I just wanted my project to be simple.