What is LED matrix?

An LED matrix or LED display is a large, low-resolution form of dot-matrix display, useful both for industrial and commercial information displays as well as for hobbyist human–machine interfaces. It consists of a 2-D diode matrix with their cathodes joined in rows and their anodes joined in columns (or vice versa).

What is the difference between RGB LED and LED matrix?

RGB matrix panel displays are fundamentally different from other types of panel displays like our Flexible LED Matrix, for instance. Whereas the Flexible LED Matrix is built from a grid of addressable WS2812B LED modules daisy-chained together, the RGB Matrix Panel is actually comprised of standard tri-color LED chips.

Control an 8x8 matrix of LEDs.

Row-column Scanning to control an 8x8 LED Matrix.

LED displays are often packaged as matrixes of LEDs arranged in rows of common anodes and columns of common cathodes, or the reverse. Here's a typical example, and its schematic:

These can be very useful displays. To control a matrix, you connect both its rows and columns to your microcontroller. The columns are connected to the LEDs cathodes (see Figure 1), so a column needs to be LOW for any of the LEDs in that column to turn on. The rows are connected to the LEDs anodes, so the row needs to be HIGH for an individual LED to turn on. If the row and the column are both high or both low, no voltage flows through the LED and it doesn't turn on.

To control an individual LED, you set its column LOW and its row HIGH. To control multiple LEDs in a row, you set the row HIGH, then take the column high, then set the columns LOW or HIGH as appropriate; a LOW column will turn the corresponding LED ON, and a HIGH column will turn it off.

Tip - Pins set to OUTPUT by use of the PinMode command are set to LOW if not otherwise stated

Although there are pre-made LED matrices, you can also make your own matrix from 64 LEDs, using the schematic as shown above.

It doesn't matter which pins of the microcontroller you connect the rows and columns to, because you can assign things in software. Connected the pins in a way that makes wiring easiest. A typical layout is shown below.

Learn how to make an LED matrix controlled by an Arduino.

Scroll down further for step by step photos and more details.

You’ll need the following parts: a prototyping board, (2) 8 pin headers, (8) 200 ohm resistors and (64) red LED bulbs.

Arrange the LEDs in the board according to the design you’ve chosen: either common row anode or common row cathode.

Solder the LEDs to the board, being careful to not to cross any of the anode or cathode leads.

Attach the 8 pin headers to feed power to the LEDs, be sure to place a 200 ohm resistor in line with each positive power lead.

Test your board for continuity with a multimeter.

Attach power to the 8 pin headers.

Today we will be starting our adventure into the deeply complex, yet totally incredible world of LED Matrices. This post is the first of an entire Arduino Matrix Programming series by Circuit Specialists.

First things first, what the heck is an LED matrix, and how does it work??

Simply put, an LED matrix is a grid of lights arranged into rows and columns. LED stands for Light Emitting Diode, so like with other diodes, electricity flows through it in only one direction – from anode(+) to cathode(-); doing so illuminates the light.

By arranging the anodes (positive side) and cathodes (negative side) in a particular way, we can achieve a matrix and call upon each LED individually by sending high and low signals from our arduino device.

Led matrices come in two arrangements. Common-row anode (left) and common-row cathode (right).

The difference between these two configurations determine how you would call on a specific LED. With common-row anode (left), the current sources (positive voltage) are attached to rows A – D. Currents sinks (negative voltage, ground) are attached to columns 1 – 4.

Conversely, with common-row cathode (right) the current sinks (negative voltage, ground) are attached to rows A – D and currents sources (positive voltage) runs through columns 1 – 4.

Applying this knowledge, to light the top-right LED (A,4) in a common-row cathode matrix you would feed positive voltage to column 4 and connect row A to ground.

We will be building this arrangement of common-row cathode matrix in this tutorial.

code

#include <TimeLib.h>

int digit1 = 10;

int digit2 = 11;

int digit3 = 12;

int digit4 = 13;

int segA = 8;//Display pin A

int segB = 7;//splay pin b

int segC = 6; //Display pin c

int segD = 5; //Display pin d

int segE = 4; //Display pin e

int segF = 3; //Display pin f

int segG = 2; //Display pin g

int segDP = 9;// Display pin dot

byte SW0 = A0;

byte SW1 = A1;

byte SW2 = A2;

void setup() {

pinMode(segA, OUTPUT);

pinMode(segB, OUTPUT);

pinMode(segC, OUTPUT);

pinMode(segD, OUTPUT);

pinMode(segE, OUTPUT);

pinMode(segF, OUTPUT);

pinMode(segG, OUTPUT);

pinMode(segDP, OUTPUT);

pinMode(digit1, OUTPUT);

pinMode(digit2, OUTPUT);

pinMode(digit3, OUTPUT);

pinMode(digit4, OUTPUT);

Serial.begin(9600);

pinMode(SW0, INPUT);

pinMode(SW1, INPUT);

pinMode(SW2, INPUT);

digitalWrite(SW0, HIGH);

digitalWrite(SW1, HIGH);

digitalWrite(SW2, HIGH);

}

void loop() {

digitalWrite(segDP, HIGH);

int hr = hour();

int timp = ( (hr>12)?(hr%12):hr)*100+minute();

Serial.println(timp);

for(int i = 250 ; i >0 ; i--) {

if (timp > 100) displayNumber01(timp);

else displayNumber02(timp);

}

for(int i = 250 ; i >0 ; i--) {

if (timp > 100) displayNumber03(timp);

else displayNumber04(timp);

}

if (!(digitalRead(SW0))) set_time();

}

void set_time() {

byte minutes1 = 0;

byte hours1 = 0;

byte minutes = minute();

byte hours = hour();

while (!digitalRead(SW0))

{

minutes1=minutes;

hours1=hours;

while (!digitalRead(SW1))

{

minutes++;

if (minutes > 59) minutes = 0;

for(int i = 20 ; i >0 ; i--) {

int timp= hours*100+minutes;

if (timp > 1000) displayNumber01(timp);

else displayNumber02(timp);

}

delay(150);

}

while (!digitalRead(SW2))

{

hours++;

if (hours > 12) hours = 0;

for(int i = 20 ; i >0 ; i--) {

int timp= hours*100+minutes;

if (timp > 1000) displayNumber01(timp);

else displayNumber02(timp);

}

delay(150);

}

for(int i = 20 ; i >0 ; i--) {

displayNumber01(hours*100+minutes);

}

setTime(hours,minutes,0,0,0,0);

delay(150);

}

}

void displayNumber01(int toDisplay) {

#define DISPLAY_BRIGHTNESS 500

#define DIGIT_ON HIGH

#define DIGIT_OFF LOW

for(int digit = 4 ; digit > 0 ; digit--) {

switch(digit) {

case 1:

digitalWrite(digit1, DIGIT_ON);

digitalWrite(segDP, LOW);

break;

case 2:

digitalWrite(digit2, DIGIT_ON);

digitalWrite(segDP, LOW);

break;

case 3:

digitalWrite(digit3, DIGIT_ON);

digitalWrite(segDP, LOW);

break;

case 4:

digitalWrite(digit4, DIGIT_ON);

digitalWrite(segDP, LOW);

break;

}

lightNumber(toDisplay % 10);

toDisplay /= 10;

delayMicroseconds(DISPLAY_BRIGHTNESS);

lightNumber(10);

digitalWrite(digit1, DIGIT_OFF);

digitalWrite(digit2, DIGIT_OFF);

digitalWrite(digit3, DIGIT_OFF);

digitalWrite(digit4, DIGIT_OFF);

}

}

void displayNumber02(int toDisplay) {

#define DISPLAY_BRIGHTNESS 500

#define DIGIT_ON HIGH

#define DIGIT_OFF LOW

for(int digit = 4 ; digit > 0 ; digit--) {

switch(digit) {

case 1:

lightNumber(10);

digitalWrite(segDP, LOW);

break;

case 2:

digitalWrite(digit2, DIGIT_ON);

digitalWrite(segDP, LOW);

break;

case 3:

digitalWrite(digit3, DIGIT_ON);

digitalWrite(segDP, LOW);

break;

case 4:

digitalWrite(digit4, DIGIT_ON);

digitalWrite(segDP, LOW);

break;

}

lightNumber(toDisplay % 10);

toDisplay /= 10;

delayMicroseconds(DISPLAY_BRIGHTNESS);

lightNumber(10);

digitalWrite(digit1, DIGIT_OFF);

digitalWrite(digit2, DIGIT_OFF);

digitalWrite(digit3, DIGIT_OFF);

digitalWrite(digit4, DIGIT_OFF);

}

}

void displayNumber03(int toDisplay) {

#define DISPLAY_BRIGHTNESS 500

#define DIGIT_ON HIGH

#define DIGIT_OFF LOW

for(int digit = 4 ; digit > 0 ; digit--) {

switch(digit) {

case 1:

digitalWrite(digit1, DIGIT_ON);

digitalWrite(segDP, HIGH);

break;

case 2:

digitalWrite(digit2, DIGIT_ON);

digitalWrite(segDP, HIGH);

break;

case 3:

digitalWrite(digit3, DIGIT_ON);

digitalWrite(segDP, HIGH);

break;

case 4:

digitalWrite(digit4, DIGIT_ON);

digitalWrite(segDP, HIGH);

break;

}

lightNumber(toDisplay % 10);

toDisplay /= 10;

delayMicroseconds(DISPLAY_BRIGHTNESS);

lightNumber(10);

digitalWrite(digit1, DIGIT_OFF);

digitalWrite(digit2, DIGIT_OFF);

digitalWrite(digit3, DIGIT_OFF);

digitalWrite(digit4, DIGIT_OFF);

}

}

void displayNumber04(int toDisplay) {

#define DISPLAY_BRIGHTNESS 500

#define DIGIT_ON HIGH

#define DIGIT_OFF LOW

for(int digit = 4 ; digit > 0 ; digit--) {

switch(digit) {

case 1:

lightNumber(10);

digitalWrite(segDP, HIGH);

break;

case 2:

digitalWrite(digit2, DIGIT_ON);

digitalWrite(segDP, HIGH);

break;

case 3:

digitalWrite(digit3, DIGIT_ON);

digitalWrite(segDP, HIGH);

break;

case 4:

digitalWrite(digit4, DIGIT_ON);

digitalWrite(segDP, HIGH);

break;

}

lightNumber(toDisplay % 10);

toDisplay /= 10;

delayMicroseconds(DISPLAY_BRIGHTNESS);

lightNumber(10);

digitalWrite(digit1, DIGIT_OFF);

digitalWrite(digit2, DIGIT_OFF);

digitalWrite(digit3, DIGIT_OFF);

digitalWrite(digit4, DIGIT_OFF);

}

}

void lightNumber(int numberToDisplay) {

#define SEGMENT_ON LOW

#define SEGMENT_OFF HIGH

switch (numberToDisplay){

case 0:

digitalWrite(segA, SEGMENT_ON);

digitalWrite(segB, SEGMENT_ON);

digitalWrite(segC, SEGMENT_ON);

digitalWrite(segD, SEGMENT_ON);

digitalWrite(segE, SEGMENT_ON);

digitalWrite(segF, SEGMENT_ON);

digitalWrite(segG, SEGMENT_OFF);

break;

case 1:

digitalWrite(segA, SEGMENT_OFF);

digitalWrite(segB, SEGMENT_ON);

digitalWrite(segC, SEGMENT_ON);

digitalWrite(segD, SEGMENT_OFF);

digitalWrite(segE, SEGMENT_OFF);

digitalWrite(segF, SEGMENT_OFF);

digitalWrite(segG, SEGMENT_OFF);

break;

case 2:

digitalWrite(segA, SEGMENT_ON);

digitalWrite(segB, SEGMENT_ON);

digitalWrite(segC, SEGMENT_OFF);

digitalWrite(segD, SEGMENT_ON);

digitalWrite(segE, SEGMENT_ON);

digitalWrite(segF, SEGMENT_OFF);

digitalWrite(segG, SEGMENT_ON);

break;

case 3:

digitalWrite(segA, SEGMENT_ON);

digitalWrite(segB, SEGMENT_ON);

digitalWrite(segC, SEGMENT_ON);

digitalWrite(segD, SEGMENT_ON);

digitalWrite(segE, SEGMENT_OFF);

digitalWrite(segF, SEGMENT_OFF);

digitalWrite(segG, SEGMENT_ON);

break;

case 4:

digitalWrite(segA, SEGMENT_OFF);

digitalWrite(segB, SEGMENT_ON);

digitalWrite(segC, SEGMENT_ON);

digitalWrite(segD, SEGMENT_OFF);

digitalWrite(segE, SEGMENT_OFF);

digitalWrite(segF, SEGMENT_ON);

digitalWrite(segG, SEGMENT_ON);

break;

case 5:

digitalWrite(segA, SEGMENT_ON);

digitalWrite(segB, SEGMENT_OFF);

digitalWrite(segC, SEGMENT_ON);

digitalWrite(segD, SEGMENT_ON);

digitalWrite(segE, SEGMENT_OFF);

digitalWrite(segF, SEGMENT_ON);

digitalWrite(segG, SEGMENT_ON);

break;

case 6:

digitalWrite(segA, SEGMENT_ON);

digitalWrite(segB, SEGMENT_OFF);

digitalWrite(segC, SEGMENT_ON);

digitalWrite(segD, SEGMENT_ON);

digitalWrite(segE, SEGMENT_ON);

digitalWrite(segF, SEGMENT_ON);

digitalWrite(segG, SEGMENT_ON);

break;

case 7:

digitalWrite(segA, SEGMENT_ON);

digitalWrite(segB, SEGMENT_ON);

digitalWrite(segC, SEGMENT_ON);

digitalWrite(segD, SEGMENT_OFF);

digitalWrite(segE, SEGMENT_OFF);

digitalWrite(segF, SEGMENT_OFF);

digitalWrite(segG, SEGMENT_OFF);

break;

case 8:

digitalWrite(segA, SEGMENT_ON);

digitalWrite(segB, SEGMENT_ON);

digitalWrite(segC, SEGMENT_ON);

digitalWrite(segD, SEGMENT_ON);

digitalWrite(segE, SEGMENT_ON);

digitalWrite(segF, SEGMENT_ON);

digitalWrite(segG, SEGMENT_ON);

break;

case 9:

digitalWrite(segA, SEGMENT_ON);

digitalWrite(segB, SEGMENT_ON);

digitalWrite(segC, SEGMENT_ON);

digitalWrite(segD, SEGMENT_ON);

digitalWrite(segE, SEGMENT_OFF);

digitalWrite(segF, SEGMENT_ON);

digitalWrite(segG, SEGMENT_ON);

break;

case 10:

digitalWrite(segA, SEGMENT_OFF);

digitalWrite(segB, SEGMENT_OFF);

digitalWrite(segC, SEGMENT_OFF);

digitalWrite(segD, SEGMENT_OFF);

digitalWrite(segE, SEGMENT_OFF);

digitalWrite(segF, SEGMENT_OFF);

digitalWrite(segG, SEGMENT_OFF);

break;

}

}