Arduino - "Blinky"
Blinky flashes LEDs from a bag of bargain leds purchased from Maplin's. I'm using four 3 pin bi-colour LEDs and one single blue LED. No other bits!
How does it work? The LED anodes are set to "high" - a fake power connection; the code toggles the cathode connections. The bi-colour LEDs change every few milliseconds; the middle LED gets rapidly updated in an inner loop - giving a smooth transistion.
The code is based on The "Hello World!" of Physical Computing. Every piece of hardware I've designed has had at least one flashing LED! You can tell so much when boards are in test, soak test, debugging.
Connecting - that's easy enough. They're on 0.1" pitch, and that means they all plug in happily with the Arduino Uno digital connector. Any bi-colour LED misconnections are trivial - the single LED won't light if misconnected.
I'm using an Arduino Uno Atmel Atmega 328 MCU board.
I'm keeping this demo simple -
so there's no jumper wires, breadboad, resistors. This is not going into production - so I'm ignoring current limiting
resistors / ATmega328 drive current / LED