# Create large Arduino powered LED sign

For a project, I need to create a large display (most likely an LED matrix) that can be controlled via Arduino. Large means probably somewhere in the neighborhood of 3' by 10". I intend to use an Arduino R3 to control the display, and it will either have a bluetooth or RF receiver module installed on it, but otherwise empty. The Arduino (and presumably the display) will be powered from a nearby wall outlet (120V). What options do I have in terms of displays to keep the cost as low as possible. (I have several people pitching in money, but I still don't want it to be too high.) From what I have seen, a large LED matrix is not only hard to find, but also very expensive. Can I just somehow link together several smaller LED matrices, or is there some other option? I have no problem doing some programming to accommodate a strange setup if it is cheaper.

Edit: The only density requirement is for it to be high enough that 1-2 lines of text filling the display is legible at a distance of about 3-6 ft. (This display will be mounted along the side of a hallway.)

• WS2812 is probably the thing you need. – venny Sep 18 '14 at 1:20
• Monochrome, 60mm x 60mm 8x8 RED LED matrix, 10-off or more for about $1.20-$2 each from China. So each one is about 2.3inches square, with 64 LEDs. That is 2-3¢/LED. The drivers will be quite complex, so you might want to use MAX7219 chips to drive them. One MAX7219 / 8x8 LED. MAX7219 appear to start around 50¢ from China. A kit with a PCB, LED matrix, MAX7219, sockets and components is just over $2 from China. Buy a couple of them, and do some experiments to get comfortable using them. 4 high x 16 long would be about 3'x10", maybe$130+? Then PCB and power. 4096 LEDs - mainly shopping – gbulmer Sep 18 '14 at 1:48
• You don't say what density of matrix you are looking for; without that information, it's hard to give advice. – Eric Gunnerson Sep 18 '14 at 4:26
• @EricGunnerson I just updated with density info – Garrett Sep 18 '14 at 23:39

## 1 Answer

Use Monochrome LEDs, 60mm x 60mm 8x8 RED LED matrix common cathode are low-cost

So each one is about 2.3inches square, with 64 LEDs.
4 high x 16 long would be about 10"x3'

LED drivers are quite complex to program. However, there is an Arduino library for MAX7219. MAX7219 is cheap, easy to get, IC to drive a monochrome common cathode 8x8 LED matrix.

One MAX7219 / 8x8 LED. They are 'daisy-chained' end to end with a few signals, so it won't be too hard to wire up a large display.

To get up and running you could get a ready made module with 8x8 LED matrix using the MAX7219. These are easy to get from web sellers. Unfortunately, the PCBs I have seen don't 'tile' fully, though you could stack two to get 16 LEDs high.

Kits with a PCB, LED matrix, MAX7219, sockets and components are available to make the same thing. You could practise making them, to see if you feel confident to make a large display.

Buy a ready made module, and a couple of kits (just in case you break the first one), and do some experiments to get comfortable using them.

Then to make a large panel you'll need PCBs. Make them in smaller pieces, maybe one to four LEDs/PCB.

If you design individual PCBs, one/LED, you could use Eagle to design the PCB.
However, 'free' Eagle has a size limit which might be awkward to overcome.

RS provide a free DesignSpark PCB package which has fewer restrictions than Eagle.

There are a bunch of low-cost PCB manufacturers on the web, that you can find with a search, who could make the PCBs for you.

If you have a friend who could make reliably make single-sided PCBs, that might be sufficient for the job (I've done a single sided PCB for something similar). Put the 8x8 LED matrix in a socket, and the MAX7219, in case things go wrong, and you want to use a commercial PCB.