ATtiny85 Xmas decorative effect, using Arduino core

This project creates a falling snowflake effect (or rain?) as discussed in this Arduino forum thread: http://arduino.cc/forum/index.php/topic,135596.15.html

The animation has a bright LED at the head, and a tail of 4 others which fall at a slightly randomised speed, with a random delay between falls. The animation slows during the fall, and the "snowflake" rests at the bottom while the tail collapses into it, before finally fading away.

Animation operates while powered on.

(legs numbered 1..8 counterclockwise from leg marked with dot)

1. Reset, no connection
2. D3 GREEN channel
3. D4 ORANGE channel
4. GND
5. D0 WHITE channel
6. D1 BLUE channel
7. D2 YELLOW channel
8. +5V

Written using the Arduino IDE and Arduino-Tiny cores (http://code.google.com/p/arduino-tiny/); the target to select is the ATtiny85 @ 8MHz (internal oscillator, BOD disabled). Look up how to program the ATtiny using Arduino, and programming it using Arduino as an IDE.

For simplicity of wiring on breadboard, and for matching to function in the code, this was wired using a colour code. A breadboard circuit diagram created in Fritzing is included to explain how two of those channels are wired.

I started the breadboard with a row of 20 LEDs, each with the flat side to the right. For a more permanent installation, rotating the LEDs so the flat side is top or bottom would allow for ease of wiring. Each group of 4 LEDs shares a direct connection to one pin directly without a resistor, with the 4 anodes (+, or the long LED leg) linked. Then the other legs are connected via a current limiting resistor to the other colours in the sequence green, orange, white, blue, yellow (always in this order, but omitting of course the colour that the anodes are).

So the green group has green to the anodes, then the cathodes in left to right sequence are orange, white, blue & yellow. The orange group has orange to the anodes, with green, white, blue & yellow to the cathodes left to right. White group's cathodes are sequenced green, orange, blue & yellow; the blue group's cathodes go green, orange, white & yellow; and the yellow group's cathodes go green, orange, white & blue.

BoM as tested:

1x ATtiny85-20PU
20x 5mm blue LED
5x 100 Ohm resistors (current limiting, for LEDs)
1x 0.1uF ceramic capacitor (decoupling)
lots of interconnecting wire!

Be sure to choose current limiting resistors to suit the particular LED you select.

Enjoy : )