Multiple Leds ... need source

[ikkeechtwel]

hello,

i've tried everything i can think of to get 18 leds working on my arduino, but couldn't find a solution,

cause i couldn't get hold of the parts,

but now i found this schematic and i got the parts,

i only need to know how to program my arduino to use it.... could you guys help me out with the source,

i've to get this working before next monday.....

http://www.arduino.cc/playground/upload ... _leds2.jpg

hope to here from you soon

bye

[adafruit]

you should post to the arduino.cc forum since the author probably reads the postings there

[ikkeechtwel]

thanx for the quick reply..

i some how came across charlieplexing... i'll have a go with it, it could do the trick. i think

bye

[Entropy]

That might work.

By the way, the schematic you linked to allows multiple LEDs to be used, but not independently. The way they're wired, a logic high from the microcontroller on the correct pin will cause the transistor to turn on, which will cause all LEDs in that schematic sample to turn on. i.e. an all-or-nothing approach.

Back in '02 my lab partner and I were too lazy to put up a webpage for our ECE 476 final project. (It has since become a requirement...) It might have been of use to you, as we were driving a scrolling LED matrix (5-6 8x5 units IIRC) from an AT90S8515 (one of the older 40-pin parts).

We were using a set of 8-bit latches for the columns, and 8 output pins from the 8515 for the rows (or possibly another latch?). The process was something like:

Put the on/off state of each LED in a row into the latches.
Strobe that row on and off
Do the same for the next row

It wasn't very efficient and had some brightness problems... There are better ways to do it.