Can it be done, and how?  

I'm trying to get startend on a project, and I want to know if it's even possible and how hard it's going to be. I'm looking to make a scrolling marquee, 30 8x8 arrays. You know, the standard 8 pins annode, 8 pins cathode. Can it be done with the ATMega168 in Arduino code? What short of hardware will I need? Is programming going to be impossible? I just need a place to start from and I think if I get the whole scope of things I will have a better idea. Thank you so much for your thoughts and ideas.....

  • Dan

It can be done without too much trouble, just a lot of tedious wiring. A commercial unit will also probably be much cheaper.

You will need a MAX7219 for each 8x8 unit. The chip connects serially to the arduino and drive the 8x8 matrix. It may be a challenge to update all 30 matricies fast enough for smooth scrolling.

Hi, the MAX7219 works fine if : - all your leds (on a single matrix) are of the same color. - you want simple on/off control for the leds

But the ATMega168 might be a bit weak for this purpose, depending on what you want to display on the matrices. Just as a hint, the ATmega168 provides 1024 bytes of ram. Just to remember the current on/off status of the leds will eat away 240 bytes. It really depends on what you are going to display.

But since a matrix using the MAX7219 provides a standard SPI-interface for the data,you can drive it from a wide range of microcomputers, even directly from a notebook through USB.

The MAX7219 is a good choice. Eberhard

Well, what I want to do with the segments is scrolling text. Nothing too fancy, maybe some transitions, but honestly nothing too complex. I was looking at the MAX7219 and I'm a bit confused on how I'm going to controll them. Could someone briefly explain how it works for the 8x8 matrix. I kinda understood about the 7 segments, but not for the 8x8. Thanks again....

-Dan

Well, what I want to do with the segments is scrolling text. Nothing too fancy, maybe some transitions, but honestly nothing too complex. I was looking at the MAX7219 and I'm a bit confused on how I'm going to controll them. Could someone briefly explain how it works for the 8x8 matrix. I kinda understood about the 7 segments, but not for the 8x8. Thanks again....

-Dan

For scrolling text, memory limits shouldn't be a huge problem. You would use the 14kB of program memory to store bitmaps of each character, then all your ram has to do is display the correct bitmaps in the right spots.

For an 8x8 matrix, you have the 64 LEDs that can each be controlled to generate an image (it could be graphical or text), each LED is 1 pixel.

This is going to be a very complex project and you'll want to start out a lot simpler. I'm pretty sure someone did a scrolling sign with a single 8x8 matrix. You might want to take a look at that as a starting point.

I understand the concept of a singel 8x8 matrix and could probably make one if I had that many led's :P The problem that I would be unsure of would be daisy-chaining all 30 of them. I just figured out that the cost of a single MAX7219 is about 5.50 which already puts the project at 165$ for the drivers and about 60$ for the 8x8's. Unless I can find an 8x8 that is longer than 2 inches I'm stuck with about 30 of them. I need to span about 6~7 feet. Do you think there might be a way to use shift registers? Or possibly another type of chip?

I understand the concept of a singel 8x8 matrix and could probably make one if I had that many led's :P The problem that I would be unsure of would be daisy-chaining all 30 of them. I just figured out that the cost of a single MAX7219 is about 5.50 which already puts the project at 165$ for the drivers and about 60$ for the 8x8's. Unless I can find an 8x8 that is longer than 2 inches I'm stuck with about 30 of them. I need to span about 6~7 feet. Do you think there might be a way to use shift registers? Or possibly another type of chip?

The MAX7219 chip is what's designed for this job. Keep in mind you need a resistor for each LED and in the matrix form, keeping the current to each one constant can be a major headache. The MAX7219 handles this for you.

You could use shift registers, 2 on each matrix for the anodes and cathodes, but the outputs couldn't power the LEDs, so you'd also need 16 transistors per matrix. You'd also have to manually scan each maxtrix in software; manually doing the multiplexing. There is no way the Arduino comes close to the computing power you'd need for that.

As I said right from the start, this will be an expensive project, more expensive than a commercial scrolling sign.

I did a little bit of searching and the closest size to what I want to make is over 800$ :o I still don't know if I am going to do this project.

Also, what about the MAX6960 - MAX6963, I saw those are about the same cost and they were designed for 2 8x8 arrays. That would effectively cut out 80 dollars, but then again I would either have to make or get some pcb's made. Some thoughts?