8x8 LED Matrix

Hey guys, I have what should hopefully be a relatively simple question here.

I recently purchased an LED Matrix from OddWires. I believe that it’s the same LED Matrix that is found on Adafruit. What I would like to do is just simply turn the entire matrix on and off with the Arduino. I’m not trying to make any fancy patterns, just all the LEDs on and all the LEDs off. I’ve tried wiring it up multiple different ways with no luck. What was closest to working was like is shown in the picture on adafruit. Here’s a simple wiring diagram that I drew up:

Obviously, the 3.3v bar will eventually be a digital pin so I can control when it’s on and when it’s off.

It never really worked how I would like. It seems that some LEDs were not getting as much power as others and were very dim. You can clearly see that here:

If anyone has any ideas on how I could make it work properly, so it looks like it does in the Adafruit image like here:

Please let me know. It would be greatly appreciated. Thanks!

Wow. At a very minimum, you need 8 current limiting resistors on either the anodes or cathodes. But it is impossible to supply the exact same current to each LED without multiplexing.

Not all LEDs are created exactly the same, there may be small variation even in the same batch. Multiple parallel LEDs aren't good for this reason. It's better to multiplex the LED matrix even if all you wanted to do is light up all 64 LEDs.

Hmm... so it appears that I should probably be using something like this? That should take care of the issue, correct?

There are quite a few ways to light an led matrix. Different chips, some easier to use, others offer more opportunity to learn interesting stuff. What do you want do do?

PaulRB: There are quite a few ways to light an led matrix. Different chips, some easier to use, others offer more opportunity to learn interesting stuff. What do you want do do?

Just want something that works tbh. All I really want to do is be able to turn all the LEDs on when an if statement is true, and turn them all off when the if statement is false.

In that case, do not use this kind of matrix. It is designed for multiplexed use, for displaying animated text and so on. You need a simple matrix where all 64 LEDs can be simultaneously be fully lit. This type of matrix cannot achieve that.

sigilwig444: Just want something that works tbh.

Use a MAX7219 then.