Inchoate

High power darlington array

What's an easy way of driving a ton of LEDs? Unfortunately the the Arduino boards can only sink or source about 40mA on each pin, which is enough to drive a few LEDs at most.

Here's how to drive up to eight LED clusters or other high current device off a single, cheap 18-pin IC with no extra components.

Arduino showing multiplexed LED matrix

To control any more than 12 LEDs on an Arduino board requires a bit of trickery. The Diecimila with its Atmega168 chip has 14 digital output pins, but you somewhat lose two from the TX/RX serial pins on 0 and 1 leaving just 12 pins. Today I built an LED matrix with 20 lights using nine pins,

The technique is to light row by row, and rely on our persistence of vision effect. Playing around with the delay it seemed like 3ms for a total of 15ms (five rows) was about the point where flicker just started being noticeable.

Geeky detail after the fold...

My first Arduino project

I've spent a very pleasant Sunday afternoon playing with an Arduino microcontroller board. After a trip to Maplin I plugged together a little array of assorted LEDs from their "lucky bags" and got hacking.