Week Z

From Robert-Depot
Revision as of 07:51, 26 May 2009 by Rtwomey (talk | contribs) (New page: Multiplexed Displays == Dot Matrix == === Circuit === http://www.best-microcontroller-projects.com/support-files/led-dot-matrix-display.pdf You will need: *5 x 470 ohm resistors *1 LN2803...)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

Multiplexed Displays

Dot Matrix

Circuit

http://www.best-microcontroller-projects.com/support-files/led-dot-matrix-display.pdf

You will need:

  • 5 x 470 ohm resistors
  • 1 LN2803 (NPN transistor array)
  • 1 4017 (decade counter)

It will use 7 output pins on your controller: 5 for the column data, one as the clock for the counter, and one to reset the clock counter. Thats pretty good.

If you are going to drive two 5x7 arrays, you can use the same clock signal and reset for both decade counters, so you will only need 12 pins total, to draw any picture you want, 10x7 pixels wide. This is pretty cool.

  • Decade counter and single data output. You will see a moving line of lights.
  • Decade counter with 5 lines of output.

Arduino Code

/*
 * Multiplexer
 *
 * Driving a multiplexed 5X7 LED display.
 * 1 clock signal drives a decade counter
 * to select lines 1-7.  1 reset pin.
 * 5 data lines drive columns 1-5.
 */

int clockPin = 8; // CP input (pin 14) on 4017 decade counter. 
int resetPin = 9; // MR (pin 15) on 4017.


void setup()                    // run once, when the sketch starts
{
  pinMode(clockPin, OUTPUT);
  pinMode(resetPin, OUTPUT);
  
  for(int j=0;j<7;j++)
    pinMode(j, OUTPUT);
  
}

void loop()                     // run over and over again
{
  for (int i=0; i<5; i++)
  {
    for(int j=0;j<7;j++)
      digitalWrite(j, HIGH);
    digitalWrite(clockPin, HIGH);   // sets the LED on
    digitalWrite(clockPin, LOW);    // sets the LED off
};
  digitalWrite(resetPin, HIGH);
  digitalWrite(resetPin, LOW);
}