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Do a google search on charlieplexing, you should get most of the information you need that way.
"charlie-plexing" is only good for having a few LED's lit a time, not for large arrays.
I would like if the lights changed in a patern but random is okay.
I thought going for a random pattern would be the simplest solution and have more readily available information.
This is an Arduino Shield of 126 charlie-plexed LEDS[...]using 12 IO pins I believe. (@20mA max)Not that I completely disagree with Soeren, but large displays with many LEDS 'on' is possible. But it is tricky, has risks, and not the most feature rich way to do it.
Looks OK in the dimmed setting it's shot, but how does it look in daylight?
You can get very efficient LED's (if you're willing to pay),
Why not just drive the outputs with FETs?
From what I hear it's ok in light. [...]Here's a 'better lit' video[...]I've bought one of these, but haven't taken the time to assemble it. It was only $25 for the whole kit. And that's after the standard Sparkfun/equiv markup of roughly 15-25% in parts price from major depos like Digi-key.
Quote from: galannthegreat on February 01, 2011, 09:54:23 PMWhy not just drive the outputs with FETs?well because using FETs if you put a 0 to the base of the FET, that would mean an 'open' circuit. In charlie-plexing you need this 'open' circuit AND ground on the same pins.
well i cannot really estimate the cost for your project unless i know the dimensions and requirements. and since i'm really lucky enough that i get most of my stuff from a very big local electronics market (one of the biggest in ASIA) , i do get it cheap....so my estimates could be slightly off ..
You lucky devil... Do they still sell transistors by the weight like groceries?