As a few may know, I'm new to the Arduino scene. I like much about it. In contrast to another microcontroller scene, it seems to me that you lot are more do-ers than idle-dreamers. I'll blog on that when I get this project squared away (3 months?). So, I've been working at a project for the few months that I have been around here. http://www.youtube.com/watch?v=okMnn39gP-8 Sorry I don't have the 'LSD' running with it - these things take time, but I wanted to demo my progress. Since the MSD data run through the LSD shift registers, I'm sure that's good and all will come right. Just a bunch of 74HC595s, their outputs going to ULN2803s; no scanning, no P-O-V. I got the LED board from an ebay-seller who was really late shipping out some smaller boards that I'd ordered, so he threw two of these in. They were part of much larger assemblies, he cut them apart with a band-saw and ended knicking many on the perimeter, which I don't use anyway. I cut all the traces between the LEDs and rewired it with each "pixel" composed of 4 wired in series, making the 5x7's. I have another board to repeat the process with, much remains to be done.
I had time to do a little soldering this afternoon and so completed the wiring between the LSD’s “pixels” and the driver board.
I need to make another, my project is < 1/2 done.
As previously stated, there’s no mux’ing, I’m just loading up the shift registers and the ULN2803s are doing the “heavy lifting”, about 10mA per. The current demand from the 12V supply is <= 280mA.
Looks good. What made you decide to go with such a brute force method?
A pixel's forward voltage, being four LEDs in series, is 8V, and that's why I had to use the 2803s (and 2803's eliminate a lot of wiring vs. transistors.) No multiplexing means no strobe flicker and brighter outputs with continuous current vs. compensating with pulse current / over-drive. Here, it's updating around 1Hz, no blinks. When I get the count-up/down going I'll have a crack at going faster.