I'm looking at starting work on 2 LED matrix's, I'm most likely going to make 2 12x12 ones. I have 2 questions I'm hoping someone can help answer them.
Firstly, which Arduino board should I go for?
Theres going to be 2, 12x12 LED displays which I'm going to solder together without a board, so they are free standing (if that makes sense), and I'd like to program 4 different profiles (though I might change it to 2 if it gets too complicated), so that they can display different patterns (I've put an image of what the patterns will be below).
Secondly, How would I connect the 2 individual 12x12 display together so that they so the same pattern?
These displays are going to be put into a visor (similar to a daft punk helmet, which is why I'm soldering the LED's without a board so I can see through the visor, I've also be painting the back of the LED's so there is as little light shining back).
I hope I've explained the questions in depth enough, any help and advice is really appreciated.
Did you think about multiplexing or driving the LEDs directly (using port extenders/ shift registers)?
Did you think about the power, the LEDs will need? 12x12x2 = 288 LEDs.
If you switch all of them on, even low power LEDs will draw 288x0.005A = 1.44Amp, which is quite a lot.
I did not think about that, that was probably going to be one of those "cross that bridge when I get to it" moments.
I'd have to use some sort of battery pack, size wouldn't really matter as I'm not looking to store power within the visor, I was going to have a battery pack on my belt or in my pocket and run a power line behind me.
I did forget to link an actual picture for some reason the wasn't working so I've attached on and linked it. http://imgur.com/mNnjm9C
The whole display wouldn't be on, at most no more then 70 LEDs would be on, so I'm not sure how that effects power usage.
As for the actual diodes, I haven't decide on which size or voltage though I'm most likely going to go for
white 3MM 3.2v – 3.8v ones for the display.
I am kind of new to the world of Arduino and it is very daunting, though I've seen it's one of the easier ways for making LED displays. I'm just not sure on what board to use, how to link the 2 12x12 displays together so they display the same pattern and now the power source.
I'd recommend you to start with an Arduino Mega since it has a lot of pins.
After that, just buy a few leds and start experimenting. You will "cross a lot of bridges"
If you're new to arduino / programming, you should be aware that you will spend lots of hours reading tutorials before you should even think about creating your matrix.
If you decide to do this, you should also be aware that - after learning a hell lot - you will be rewarded with a lot of fun and a better understanding to all those electronic devices around you.
Thank you I'll have a look at the Mega board, I did see someone run a 8x8 display from a Uno board, which I might look at doing instead as alot of tutorials I've looked at use that sized display, which I might do and just use larger LEDs something like 5mm 3V.
Plan before you do any soldering. Soldering is a bridge you can't uncross (easily).
I don't think you need to spring for a Mega or any special Arduino, especially if this is a wearable project.
Consider the MAX7219 chip. Each one controls 64 LEDs with its own multiplexing scheme, so you aren't powering all LEDs with constant current and wasting all that power. You'll also save a ton of time and headache as you don't have to resistor-ize every single LED because the chip controls current as well.
So you'll see that you have to connect that chip to the arduino. But start without it first, since its quite complex for someone with no experience in programming/electronics.
Thought I would just do a quick update as I have some questions on what to do next. I've managed to make a test 8x8 matrix with some 3mm 3.0v blue LEDs. On the final peice I will be making 2 8x8 display with white LEDs.
I also got a bunch of 120 Ohm resistors and 2 MAX7219 drivers.
So I've checked the LEDs and they work, bar one which I think just needs replacing.
So my questions are,
How to connect the 1 of the MAX drivers to the matrix? Do I just connect them to the anodes? I've had a google but unfortunately any tutorial I find, everyone's using the pre built displays (I think they're made by adafruit).
Connect the Arduino via USB to my PC. Will that also power it (while I'm testing it) or do I need an independent power source.
I hope I did my maths right on the resistors, but so I use one per row (8 resistors in total).
And those prebuilt displays are just 64 leds with 16 pins like what you probably built, 8 pins for rows, 8 for columns.
Data sheet spells it out. Segment pins for anode columns, Digit pins for cathode rows.
Just an extra 2c...
If you are going with 2x 7219 (one for each eye), you can cascade the displays if you think about it, so mirroring, crawling patterns across the two eyes is quite easy.
One advantage of the Mega chips - is having extra FLASH and RAM to manipulate and store additional LED patterns.
Once you have everything hooked up, simple static patterns are easy, but with a little extra thinking, you can animate and achieve other effects.
