NerdKits has put together a video that describes how a LED row/column matrix is wired. This comes in handy when you have limited pins and need to control lots of items. Another popular method is to use a serial to parallel latch.
"This project makes use of row-column addressing, which lets us control lots of LEDs without having one wire going to each one. We also use one more trick — the fact that diodes only conduct in one direction — to double the number of LEDs you can handle with the ATmega168 microcontroller. "
Permalink
Permalink
Always informative! LED is the future of lighting.
Permalink
By switching the polarity and driving the led with a backward current you will destroy them in the near future.
better way is to adress the rows and colums by multiplexer ics.
Permalink
It is actually safe Chris LEDs have a reverse voltage range, as long as the reverse biased voltage is within that range you will be fine. It is usually in the 5 or 6 volt range. There are actually 2 lead LEDs that have two internal LEDs and depending on which one is forward biased it will light and the other will not conduct and stay dark.
http://www.scienceprog.com/bi-color-led-indication/
Permalink
Not to be mean but invented? AFAIK this is known as charlieplexing and is nothing new!
I don’t mean to be rude, but misinformation is something I dislike =)
Permalink