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1  Using Arduino / LEDs and Multiplexing / Re: LED screen on: January 25, 2013, 09:40:51 am
Thank you both! I removed the Serial printing and it's now working  smiley
2  Using Arduino / LEDs and Multiplexing / LED screen on: January 24, 2013, 12:42:15 pm
Hi all,
I'm building an LED screen. Right now  it's 3x3. The problem is that I'm trying to make it display some images but it doesn't stop flickering. Does anyone know why is it happening? Here is the code I'm using. I'm receiving a String from processing with the states for each LED on. I added an image of the connections at the end of this post

Thanks in advance.

char val;
String data = "";

int pinColumn = 11;
int pinRow = 8;

const int ancho = 3;
const int alto = 3;

int leds[ancho*alto];

int matrizLeds[ancho][alto];
int contador = 0;

int temporal[alto];
char recibido[ancho*alto];

int counter = 0;
void setup()
  for(int i=8; i<15; i++){
    pinMode(i, OUTPUT);
  for(int i=0; i<ancho*alto; i++){
    leds[i]= 0;

void loop()
  if (Serial.available())
    val =;
    if (val != 'L')
      recibido[counter] = val;
      leds[counter] = int(recibido[counter]);
      counter = 0;
      contador = 0;
      for(int i=0; i<alto; i++) { // row scan
        for(int j=0; j<ancho; j++) { // column scan
          matrizLeds[i][j] = leds[contador];
          contador ++;

void encenderLeds() {
  for(int i=0; i<ancho; i++) { // row scan
    for(int j=0; j<alto; j++) { // column scan
      if(matrizLeds[i][j] == 49){
        Serial.print("entre i=");
        Serial.print(" j=");
        digitalWrite(i+pinColumn, HIGH);
        digitalWrite(j+pinRow, LOW);
        digitalWrite(i+pinColumn, LOW);
        digitalWrite(j+pinRow, HIGH);
3  Using Arduino / General Electronics / Re: Changing ceramic capacitors to electrolytic on: December 03, 2012, 07:36:35 am
Thank you very much!
4  Using Arduino / General Electronics / Re: Changing ceramic capacitors to electrolytic on: December 03, 2012, 07:25:16 am
oh... ok.. thanks!
Another question...I've been checking the diagram more deeply but I'm not sure what everything means.. I'm supposed to connect a piezoelectric in this circuit but I'm not really sure where should I put it  smiley-confuse. Also, I don't understand what Vbias means...
Thanks again! =)
5  Using Arduino / General Electronics / Changing ceramic capacitors to electrolytic on: December 03, 2012, 06:45:19 am
Hi all,
I'm working on a project and I want to build the circuit in the image. I wanted to know if I can replace the ceramic capacitors that are shown in the diagram for electrolytic capacitors. If so, how should I connect them? I mean, how should I manage the electrolytic's polarity?
Thanks in advance!
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