I'm planning to build a scrolling LED display with my Arduino. One thing I think I'll need, is shift registers.
It'll be a grid 7 high x however wide. Arduino will be driving the 7 row pins therefore, and the shift register providing ground for each column. Unless the other way's better for some reason.
The idea would be to keep the shift registers full of '1's, right? With one '0' that I circulate round with each tick, to selectively provide ground for a column at a time. Clocked by an Arduino pin.
My main worrry, I think, is current capacity. How much should I be feeding the LEDs? Do I need resistors to limit current or does the low duty cycle make that unimportant? More importantly, and this is my question, what shift register do I use? It'll have to sink up to 7 LEDs at a time. It's actually a bugger looking up current ratings on component suppliers, it's always in the PDF, never available on the page. So what technology do I use? CMOS, TTL, HCT etc?
If you're naming suppliers, UK would be best since it's where I am, but just part numbers will be fine.
Any hints on this, I'd be grateful! I'll probably start off with just a couple of the 7x5 modules for the display, then build up once I get it working. AFAIK you can drive a good few dozen columns in this way while keeping decent brightness. Ta!