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Tag: Arduino


I got a simple motor from a broken domestic printer. It’s a Mitsumi m355P-9T stepping motor. Any other common stepping motor should fits. You can find one in printers, multifunction machines, copy machines, FAX, and such.

bumbabot v01

With a flexible cap of water bottle with a hole we make a connection between the motor axis and other objects.

bumbabot v01

bumbabot v01

With super glue I attached to the cap a little handcraft clay ox statue.

bumbabot v01

It’s a representation from a Brazilian folkloric character Boi Bumbá. In some traditional parties in Brazil, someone dress a structure-costume and dances in circular patterns interacting with the public.


Photos by Marcus Guimarães.

Controlling a stepper motor is not difficult.  There’s a good documentation on how to that on the Arduino Stepper Motor Tutorial. Basically it’s about sending a logical signal for each coil in a circular order (that is also called full step).

full step

Animation from

stepper motor diagram

You’ll probably also use a driver chip ULN2003A or similar to give to the motor more current than your Arduino can provide and also for protecting it from a power comming back from the motor. It’s a very easy find this tiny chip on electronics or automotive  stores or also from broken printers where you probably found your stepped motor.

Arduino Stepper Motor UNL2003A

With a simple program you can already controlling your motor.

// Simple stepped motor spin
// by Silveira Neto, 2009, under GPLv3 license
int coil1 = 8;
int coil2 = 9;
int coil3 = 10;
int coil4 = 11;
int step = 0;
int interval = 100;

void setup() {
  pinMode(coil1, OUTPUT);
  pinMode(coil2, OUTPUT);
  pinMode(coil3, OUTPUT);
  pinMode(coil4, OUTPUT);

void loop() {
  digitalWrite(coil1, step==0?HIGH:LOW);
  digitalWrite(coil2, step==1?HIGH:LOW);
  digitalWrite(coil3, step==2?HIGH:LOW);
  digitalWrite(coil4, step==3?HIGH:LOW);
  step = (step+1)%4;

Writing a little bit more generally code we can create function to step forward and step backward.

My motor needs 48 steps to run a complete turn. So 360º/48 steps give us 7,5º per step. Arduino has a simple Stepper Motor Library but it doesn’t worked with me and it’s also oriented to steps and I’d need something oriented to angles instead. So I wrote some routines to do that.

For this first version of BumbaBot I mapped angles with letters to easy the communication between the programs.

motor angle step control

Notice that it’s not the final version and there’s still some bugs!

// Stepped motor control by letters
// by Silveira Neto, 2009, under GPLv3 license

int coil1 = 8;
int coil2 = 9;
int coil3 = 10;
int coil4 = 11;

int delayTime = 50;
int steps = 48;
int step_counter = 0;

void setup(){
  pinMode(coil1, OUTPUT);
  pinMode(coil2, OUTPUT);
  pinMode(coil3, OUTPUT);
  pinMode(coil4, OUTPUT);

// tells motor to move a certain angle
void moveAngle(float angle){
  int i;
  int howmanysteps = angle/stepAngle();
    howmanysteps = - howmanysteps;
    for(i = 0;i

In another post I wrote how create a Java program to talk with Arduino. We'll use this to send messages to Arduino to it moves. 


[put final video here]

To be continued... 🙂

Arduino and Java


Arduino is a free popular platform for embedded programming based on a simple I/O board easily programmable. Interfacing it with Java allow us to create sophisticated interfaces and take advantages from the several API available in the Java ecosystem.

I’m following the original Arduino and Java interfacing tutorial by Dave Brink but in a more practical approach and with more details.

Step 1) Install the Arduino IDE

This is not a completely mandatory step but it will easy a lot our work. Our program will borrow some Arduino IDE libraries and configurations  like which serial port it is using and at which boud rate. At the moment I wrote this tutorial the version of Arduino IDE was 0013.

Step 2) Prepare your Arduino

Connect your Arduino to the serial port in your computer. Here I’m connecting my Arduino with my laptop throught a USB.


Make sure your Arduino IDE is configured and communicating well if your Arduino. Let put on it a little program that sends to us a mensage:

void setup(){

void loop(){
  Serial.println("Is there anybody out there?");

Step 3) Install RXTX Library

We will use some libraries to acess the serial port, some of them relies on binary implementations on our system. Our first step is to install the RXTX library (Java CommAPI) in your system. In a Debian like Linux you can do that by:

sudo apt-get install librxtx-java

Or using a graphical package tool like Synaptic:

installing rxtx

For others systems like Windows see the RXTX installation docs.

Step 4) Start a new NetBeans project

Again, this is not a mandatory step but will easy a lot our work. NetBeans is a free and open source Java IDE that will help us to develop our little application. Create a new project at File → New Project and choose at Java at Categories and Java Application at Projects.

netbeans new project

Chose a name for your project. I called mine SerialTalker.

name your project

At the moment I wrote this tutorial I was using Netbeans version 6.5 and Java 6 update 10 but should work as well on newer and some older versions

Step 5) Adding Libraries and a Working Directory

On NetBeans the Projects tab, right-click your project and choose Properties.


On the Project Properties window select the Libraries on the Categories panel.

Netbeans project libraries

Click the Add JAR/Folder button.

arduino directory

Find where you placed your Arduino IDE installation. Inside this directory there’s a lib directory will some JAR files. Select all them and click Ok.

jars libraries

As we want to borrow the Arduino IDE configuration the program needs to know where is they configuration files.  There’s a simple way to do that.

Still in the Project Properties window select Run at Categories panel. At Working Directory click in the Browse button and select the directory of your Arduino IDE. Mine is at /home/silveira/arduino-0013.

Working directory

You can close now the Project Properties window. At this moment in autocomplete for these libraries are enable in your code.

netbeans autocomplete

Step 6) Codding and running

Here is the code you can replace at in your project:

package serialtalk;


public class Main {
    static InputStream input;
    static OutputStream output;

    public static void main(String[] args) throws Exception{
        System.out.println("Using port: " + Preferences.get("serial.port"));
        CommPortIdentifier portId = CommPortIdentifier.getPortIdentifier(

        SerialPort port = (SerialPort)"serial talk", 4000);
        input = port.getInputStream();
        output = port.getOutputStream();
            while(input.available()>0) {

Now just compile and run (with your Arduino attached in your serial port and running the program of step 2).


There is. Now you can make your Java programs to talk with your Arduino using a IDE like NetBeans to create rich interfaces.

Morse Code Translator with Arduino

You write in your computer, sends a message thought USB and Arduino translates it into a Morse code.

Just a Arduino board with a buzzer connected at the digital output 12 (one wire in the ground and the other in the 12).


I tried to make the code as general as possible so you can easily adapt it for anthers ways of transmitting a Morse code. To do that you just need to rewrite a few functions.

                                                  | 3) Interpretation |
                                                  |   2) Translation  |
+-------------------+                             +-------------------+
|     Computer      |<========USB (Serial)=======>|     1) Reading    |
+-------------------+                             +-------------------+

  1. Reads a character from Serial. Main function loop().
  2. Translate a ascii char into a Morse code using a reference table. A letter ‘K’ becomes a string word “-.-“. Function say_char().
  3. Interpret the Morse word as light and sound. Mostly at function say_morse_word(). The Interpretation needs 5 functions to say all Morse words, dot(), dash(), shortgap(), mediumgap() and intragap().

For a more details on Morse code I strongly recommend the English Wikipedia article on it.

int led = 13;                   // LED connected to digital pin 13
int buzzer = 12;                // buzzer connected to digital pin 12
int unit = 50;                  // duration of a pulse

char * morsecode[] = {
    "-----",  // 0
    ".----",  // 1
    "..---",  // 2
    "...--",  // 3
    "....-",  // 4
    ".....",  // 5
    "-....",  // 6 
    "--...",  // 7
    "---..",  // 8
    "----.",  // 9
    "---...", // :
    "-.-.-.", // ;
    "",       // < (there's no morse for this simbol)
    "-...-",  // =
    "",       // > (there's no morse for this simbol)
    "..--..", // ?
    ".--._.", // @
    ".-",     // A
    "-...",   // B
    "-.-.",   // C
    "-..",    // D
    ".",      // E
    "..-.",   // F
    "--.",    // G
    "....",   // H
    "..",     // I
    ".---",   // J
    "-.-",    // K
    ".-..",   // L
    "--",     // M
    "-.",     // N
    "---",    // O
    ".--.",   // P
    "--.-",   // Q
    ".-.",    // R
    "...",    // S
    "-",      // T
    "..-",    // U
    "...-",   // V
    ".--",    // W
    "-..-",   // X
    "-.--",   // Y
    "--.."    // Z

void setup() {
  pinMode(led, OUTPUT);
  pinMode(buzzer, OUTPUT);

void say_morse_word(char * msg){
  int index = 0;
    // say a dash
    // say a dot
    // gap beetween simbols

// beep
void beep(int time){
  int i;
  int t = 100; // period of the wav. bigger means lower pitch.
  int beepduration = (int)((float)time/t*1800);
  digitalWrite(led, HIGH);
    Serial.print(' ');
  } else {
    if(letter==' '){
      Serial.print(" \\ ");

void loop(){

Additionally you can put another function to say entire strings, like say_string(“HELLO WORLD”)

void say_string(char * asciimsg){
  int index = 0;
  char charac;  
  charac = asciimsg[index];
    charac = asciimsg[++index];

You can use the Arduino IDE itself or any other program that talks with the serial port USB.

arduino interface

Arduino on Ubuntu


My Arduinos arrived yesterday. It’s a programmable open source and hardware device.

To install its software on my Ubuntu 8.10 I need Java installed and some tools that I could get by:

sudo apt-get install avrdude avrdude-doc avrp avrprog binutils-avr gcc-avr