[sigplus] Critical error: Image gallery folder ledSign is expected to be a path relative to the image base folder specified in the back-end.
Every 2 years my local school system had an auction. This time, I picked up a large LED sign for $22.50.
The sign had a power cable, a couple of ports, and a label that read "Data Design Corp." I bought the unit assuming that I wouldn't be able to get any datasheets or manuals for it, but I did some searchign anyway. I ended up talking to a former VP of the company, who told me the company had been sold and dismanteld years ago.
At this point I had 2 options. The first was to try to figure out the connections on the controller board, and reverse engineer some kind of interface.The second option was to ditch the controller board all together and build one from scratch.
In the end I deicded to go with the second option. While working witht he original control board would be interesting (and a good excuse to finnaly buy a Bus Pirate), I decided it was a bad idea. For one thing, I had no clue what the status of the control board was - when the unit is powered on, no lights appear. For all I knew, the board could be dead. Secondly, I had no clue what the process to make this work would be. Would I use a keyboard to type a message, and store it to memory? What kind of communication protocol and termination would I need to use? Finally, I couldn't be sure that I'd even hav epiel level control. If this display was meant only to scroll text, it might not support the user programming new bit patterns. That would stop me from using differenr character sets, or playing games like pong or Conway's Game of Life.
At first, I was a little overwhelemed by this project. 2688 LEDs is much more than I've worked with before. However, I broke down the circuits bit by bit, and made alot of progress.
First, I found that the display was comprised of 4 smaller 14x48 LED boards. Then, I figured out that groups of 4 LEDs were wired in series to make a 'pixel'. Suddenly I had a 7x24 pixel board, which was quite a bit more manageable
I was even more relieved to find that each board had three 8-bit shift registers. As I followed the circuits, I found that one of the modular connectors on the board where tied as they should be for shift registers. This meant that I could control the 24 columns (and eventually all 96 columns) with three data pins
The other modular connector ended up tying to the 7 rows. As i suspected, the board is using a standard LED multiplexing setup to draw the display.
The system requires some power circuitry, but using the 10 pins on the arduino (less if I use a decade counter or a BCD converter) I can control the display
I'm still working out alot of bugs in the code, but the video shows my progrss so far. Soon I should have it working to a point that I can put the panels back in the display and hang it up somehwhere. I'm still deciding on the method I want to generate data to display. I'm thinking of getting a Ethernet Sheild and making the sign read RSS feeds or something.
Click on each photo for more information.
- Progress Reports
- Arduino Code
- More Videos and Pictures