I have an Arduino Uno, using a MAX7219 to control a 8x8 Bi-color led matrix.

The problem however, is that upon activating a 5th led in the matrix, the unit "dies", in lack of a better word. I can activate any arbitrary combination of 4 leds, but upon the activation of a fifth, the matrix flashes promptly and goes blank.

What kind of problem does this sound like? Improper resistor value? Grounding or inadequate power?

UPDATE: Upon disconnecting the wire grounding the breadboard to the Arduino, all the desired leds are lighting up in my expected pattern, except with a low-intensity brightness.

UPDATE 2: Fritzing didn't have a resembling matrix model, and I'm not doing this by hand now. I have wired (to my understanding) like in this schematic, with both the 5V and RSet coming from the MAX7219 onto the power line of the breadboard, RSet via a 10k resistor.

Here are two pictures of the current setup: 1, 2.
2 ground wires as per the MAX7219 Datasheet, DIG0-7 on columns, SEGDP-G on rows, RSet to 5V via 10k resistor and normal 5V.

I am obviously new to this and I don't mean to ask stupid questions so please be patient.

Are there any logical flaws in these pictures?

  • 4
    \$\begingroup\$ A schematic would be most appreciated \$\endgroup\$
    – Adam Head
    Sep 29, 2014 at 13:15
  • 1
    \$\begingroup\$ Haven't made one yet, gimme a few. \$\endgroup\$
    – krystah
    Sep 29, 2014 at 13:16
  • \$\begingroup\$ Downvoted because "gimme" isn't a proper word! \$\endgroup\$ Sep 29, 2014 at 13:19
  • \$\begingroup\$ Added a link to the schematic I followed. \$\endgroup\$
    – krystah
    Sep 29, 2014 at 13:32
  • \$\begingroup\$ What are you using to power everything? \$\endgroup\$
    – Grant
    Sep 29, 2014 at 17:26

1 Answer 1


It sounds like a inadequacy of power to me based on the information you've provided. I believe this to be so due to a similar experience with a Dot-Matrix display. I was able to light only so many blue LEDs, until the power supply cut the power for overload protection. Upon upgrading to a 5 ampere power supply, I no longer experienced that issue.

  • \$\begingroup\$ This answer may well be correct based on the minimal information that was provided, so why the downvote? +1 from me. \$\endgroup\$
    – Tut
    Sep 29, 2014 at 13:51
  • 2
    \$\begingroup\$ nice and succinct answer from a newbie, nice work. \$\endgroup\$
    – KyranF
    Sep 29, 2014 at 14:51
  • \$\begingroup\$ Updated my question. If you got further insight it will be appreciated. \$\endgroup\$
    – krystah
    Sep 29, 2014 at 15:13

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