8X8 LED Display board

The silkscreen on this board says LC8x8 (for low-cost I guess). However in the service of not getting it mixed up with my LCD board the name has been changed to the (prosaic) 8x8LED board. I'll change the silkscreen on the next respin of the board.

This is a board I burned with the idea of providing a non-multiplexed 8x8 LED display for higher powered LED applications. The driver chips have constant current sources built in, the brightness / current draw of which is set by one resistor. The board will accommodate either through-hole or the larger sized surface mount LED's. The panels are 3.200" square and tile seamlessly, allowing one to build LED displays of any size, or even cruciform layouts.

The data interface to the board is a standard SPI (synchronous serial protocol) with a clock, data, and chip select line. There is also an enable line that is brought out to the interface header. To add more panels, just solder jumpers from one panel to the next. The data outputs on one panel line up with the data inputs on the next so the wiring is painless.

This is a board which maybe shouldn't be through-hole design but a lot of what I design is for education / artists / hobbyists and at least some of my audience has never soldered surface mount components. Surface mount wouldn't have made the board smaller anyway, because the larger size was by choice, but the it might have simplified the board design.

The green boards were the prototypes, the production boards, which are shipping, are black, with white screenprint on the parts side only. I'm leaving the photos of populated green boards up here though, as they make the parts layout more clear.

That is an older Rev B BBB hanging off the back of the display board. The glimpses of orange you see is a power wire I stubbed in. The production display boards will mate with no fuss. I wasn't smart enough to think that far ahead as the prototypes of the BBB rev C boards were in the same batch as this prototype. The good news is that there is still almost 10K of space left in the Arduino sketch after loading in the character set and all three of Asimov's Laws of Robotics. So you can easily get the whole Gettysburg Address on the chip. But probably not Genesis.

I programmed a little utility that takes the pain out of generating the integers that control the display. Just draw your character and copy and paste. Mac and Windows files for the utility are below. Let me know if there are more features you want in it.

Mac 8x8 Character Display Calculator
Windows 8x8 Character Display Calculator

More pictures of how the panels daisy-chain here. There are only four wires, and power and ground to connect. The holes all line up on the edges of the panels. Just layout the panels however you wish and solder them together.

One caveat is that data line only must flow out of one panel (DO) and get connected to the data input (DI) of another. This would may require running one wire around the back of a panel here or there, but its easy.

Files:

Instructions for the 8x8 LED panel.

Fairly low-res video of a two-panel sign. The panels are high-brightness blue LED's and generic green LED's so there is a big jump in brightness as the color changes across the two panels.

My video camera died right after I shot this. The odd, glitchy pause was an unrecognized portent of camcorder death, I believe, and is not present in the sign.

Here's my Arduino file, for the curious. There is slightly less than 10K, still free on the chip.

8x8 LED Display Board

Printed Circuit Board Only

LC8x8 PCB only
1	$8 + .75
4	$24 + 1.39
10	$50 + 3.20
Partial shipping figures are in blue. Please visit the shipping page to complete your order.

8x8 LED Display Board Kit

Includes PCB four driver chips 1k resistors and capacitors, headers to mate with a Bare Bones Board, but no LED's.

8x8 LED Board Kit
1	$20 + 1.10
4	$70 + 3.46
10	$160 + 9.40
Partial shipping figures are in blue. Please visit the shipping page to complete your order.

8x8 LED Display Board Kit Plus Bare Bones Board

Everything you need to build a one panel or two, or four panel sign except the LED's

Kit's include 1 Bare Bones Board, (1,2 or 4) LC8x8 PCBs, 4x driver chips, resistors and capacitors, mating headers, but no LED's.

LC8x8 Kit with Bare Bones Board
1 panel kit	$30 + 1.24
2 panel kit	$50 + 2.69
4 panel kit	$80 + 4.10
Partial shipping figures are in blue. Please visit the shipping page to complete your order.