led matrix

im a beginner using arduino and i am having trouble writing a code to display a text on my led matrix. i want to start simple with just one letter or picture not a scrolling text. my led matrix is premade and i have it wired to the individual pins not to a MAX1721 or anything. can anyone help me!!! i have done some research and came across something called a byte very often but cant seem to get it to work. i can light up individual rows and columns but i cant make images.

Should really get a MAX7219 module on eBay.

That's if you seriously want to use the matrix. Otherwise, it is a cute but rather pointless educational exercise. :grinning:

OK, OK, search for "multiplexing".

ok thank you i saw someone do it without the module so i thought it wouldnt be that hard. Any other poiters i could use though?

firstimer12:
ok thank you i saw someone do it without the module so i thought it wouldnt be that hard.

Hi,

Was that on an “Instructable” by any chance? If so, it probably worked either very poorly/dimly, or was damaging the Arduino by overloading its pins.

If you want something that works well and does not damage the Arduino, then the max7219 really is the simplest way to do it. One chip, one resistor, a couple of caps and 3 Arduino pins.

If you want to learn about how multiplexing works and do it without the max7219, and have it work well without damaging the Arduino, you could use:

  • 8 npn transistors (e.g. BC337), plus 8 series resistors, 8 base resistors and a couple of caps, and 16 Arduino pins
  • a ULN2803 chip, plus 8 series resistors and a couple of caps, and 16 Arduino pins
  • a TPIC6C595 chip, plus 8 series resistors and a couple of caps, and 11 Arduino pins

Let us know which way you want to go.

Paul

To get back to your original question, and purely for that "educational" matter, you need to understand multiplexing.

You need to post, according to the instructions,

  • Your circuit
  • The "instructable" that you copied
  • A photo of your assembly
    You can do it as a demonstration, using eight 1k2 resistors.

Any other poiters i could use though?

Have a read of this
http://www.thebox.myzen.co.uk/Workshop/LED_Matrix.html
It explains the fundamentals of multiplexing.

ok thank you very much. i think i will jus go get the MAX7219 chip to make it easier.