Hello!
I'm new to Arduino forum and coding (the stuff is like matrix to me). But I'm eager to learn and get my project on the way.
I want to make a grid of MAX7219 LED Modules connected to each other (around 100 of them).
Each individual would have to run a a certain sequence of numbers (like a counter) From 0 upwards.
My questions are;
Is this possible to do?
What will I need?
And how hard would the code be to write for this contraption?
Thanks
David
Perhaps you had better explain the purpose of this, how many digits per module and exactly what these counters will represent.
This would be a part of an installation for my final major project, the amount of digits running per module would vary from 8 to 4 and the digits would represent statistics gathered from a variety or different sources . I would like them to run in a loop.
So you want to use pre-built modules such as this:
Dirt cheap and readily chain-able (but you must bypass that diode on the back). There is no way you would consider assembling that quantity yourself. 
You need to explain your meaning of "to run in a loop". The advantage of the MAX7219 is that it performs the multiplexing - you send the information to it and that information is continuously displayed until you want to show something different.
Yes that's exactly what I want, I already have 3 of them as you can see in the photo attached.
Running in a loop I meant I just want it to start counting up again once it's finished.
I've attached an image of what I have so far and also a sketch of what I want the final piece to look like (it's not great, but hopefully it'll make more sense).
OK, so you are on your way.
Note what I said about the diode on the back of the module. If you simply chain them as you illustrate, you lose 700 mV at each step. There is a fault in the circuit on the module - the diode is intended to protect against accidental reverse polarity supply.
You need to arrange to supply power (5 V and ground) separately from a heavy cable (like house wiring) which (with minimal distance) branches to the input side of each module while the data connections chain from one to the next. Of course you cannot use the 5 V from the Arduino; you need a separate power supply.
You will also need buffers for every 8 or 10 modules - a 74HC14 with two inverters in series on each of the three lines. It may be easier just to provide a separate Arduino Nano clone (or in fact, Pro Mini - you only use UNOs for experimentation) to operate five chains of eight modules each, using a separate three control lines (thus total 15) for each chain.
I am not sure from your description whether the displays are supposed to reflect real input data, or a random presentation.
