MAX7219 problems, single LED

Projects Programming
1

Hi everyone,

I designed a 8X7 LED matrix powered by MAX7219 for a project. I am trying to test it with Arduino by powering only one LED at a time. The issue is that some LEDS are glowing while some are not glowing. I attached here my code, PCB design (I designed it) and video to describe my issue. Could you please let me know where I am doing wrong. I have 4 MAX7219, so tried interchaging them, nothing worked. I checked my connections as many times as possible, both with eye and also with a multimeter continuty. I am going mad with this issue, so posting here for help.

#include "LedControl.h"

/*
 Now we need a LedControl to work with.
 ***** These pin numbers will probably not work with your hardware *****
 pin 12 is connected to the DataIn 
 pin 11 is connected to the CLK 
 pin 10 is connected to LOAD 
 We have only a single MAX72XX.
 */
LedControl lc=LedControl(12,11,10,1);



unsigned long delaytime=100;

void setup() {
  /*
   The MAX72XX is in power-saving mode on startup,
   we have to do a wakeup call
   */
  lc.shutdown(0,false);
  /* Set the brightness to a medium values */
  lc.setIntensity(0,8);
  /* and clear the display */
  lc.clearDisplay(0);
}



void loop() { 

 for(int row=0;row<7;row++) {
    for(int col=0;col<7;col++) {
      lc.setLed(0,row,col,true);
      delay(delaytime);
      lc.setLed(0,row,col,false);
      delay(delaytime);
                  }
           }

}

875×654 46.1 KB

3120×4160 1.79 MB

2

Hi,
A schematic would help too.

Thanks.. Tom.. :slight_smile:

3

Thanks, Tom for the reply.

I have no schematic. This is my first board designed in eagle. I am posting my schemtic figure from Eagle as it is. I know this might be a bad way of designing the project. I also attached the original eagle files here.

751×703 6.13 KB

4

Hi,

Please read the post at the start of any forum , entitled "How to use this Forum".
OR
http://forum.arduino.cc/index.php/topic,148850.0.html.

It will show you how to post images.

Why don't you have a schematic, that is a circuit diagram.
Remove the MAX chip and use a DMM to test your LED circuits.

Did you draw a circuit in Eagle as well?
If so please post an Export image in jpg for us please?

Are you sure your LEDs are all soldered the same way?

Tom... :slight_smile:

5

Hi Tom,

Thanks for your reply. Sorry for the picture attachement. I cleaned that up now.

I mean, I kind of worked on the board window in eagle while looking at the pin. I didn't draw the circuit in eagle.
I am sure about the LEDs being soldered correctly. That is first thing, I have checked. I am going to check the other thing you posted about checking each LED by removing the MAX7219 chip. I will reporrt back on this asap.

6

Hi Tom, I can confirm that individually each LED is working fine. I checked with an external power source.