LED Matrix with Arduino

Discussion in 'General Electronics Chat' started by ipndrmath, Jul 8, 2010.

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  1. ipndrmath

    Thread Starter New Member

    Jul 8, 2010
    Hey Guys -

    So ultimately my plan is to build an underglow kit for my '55 Ford, and seeing how I couldn't find any tutorial of the sorts, I figured this would be a great opportunity for me to contribute. The first step, however, is to figure out what it is that I'm doing. :)

    Here's what I've already done:

    Set up this 8x8 LED matrix, with the Arduino Main Board and MAX7219CNG as the LED driver. With this setup, I was able to drive all 64 pixels (and in this case, LEDs) independently. For those of you that are unfamiliar with the MAX72xx series, it's basically just an LED driver that handles the Multiplexing Code for you and makes it such that you only need one resistor for the entire display.

    Here's what I need to do now:

    Set up ~400 Bright LEDs in a multiplex design with 64 pixels (~6 LEDs per pixel) and connect this monstrosity to some sort of an LED driver.

    Here's the products I'm thinking of:

    These LEDs which have a Forward Voltage of 3.3~3.5V, a Forward Current of 20mA, and a Luminosity of 6~8k mcd (not that it's really relevant to my questions). $80 for 500.

    Using one of the Arduino Boards which can output voltage at 3.3 or 5V.

    I would really like to stay with the
    MAX7219CNG if at all possible as there exists a very nice library for the driver. To be honest, the datasheet confuses me a bit, but it appears that the driver outputs voltage of:
    Code ( (Unknown Language)):
    1. V+ -1
    where V+ is the input voltage which has a MAX of 6V. As for current, I haven't any clue what's what. It's in the datasheet somewhere, but, as I said, I get a little lost.

    Also note that the driver can accept V+ from a source other than the Arduino Board and that the driver requires one resistor (or rather a number of resistors, but they are all in the same series).

    Here's the questions I have:

    How do I go about figuring out what Voltage and Current I need for the Matrix?

    In the Matrix are there 8 Series of LEDs or are they Parallel?

    Based on the first question, how can I tell if the LED drive listed will suffice?

    Am I going to need to amplify the electrical signal once it passes through the Driver to power the ~48 LEDs per row?

    My little disclaimer

    I know that this has something to do with Ohm's law, but it's been a few years since I've really understood which version of which equation is used where.

    Thanks in advance you guys!
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    Well, the current is going to depend on the driver and how its lighting the leds.

    If it is a POV/PWM design, you do not require as much current as just putting a constant supply to the LEDs.
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    Last edited: Jul 8, 2010
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