(right dice was the first one)

Tutorial for a DIY dice with Attiny85, Tilt sensor, Charlieplexing, Crystal resin.

it's easy way to build your own little electronic dice for good price.

French version on my blog

Inventory list

Attiny 85 with socket
Tilt sensor
Led
39 ohms resistors
Crystal resin
gloss for crystal resine
ice cube tray 3x3x3 cm

Step 1: Wiring the Dice

Charlieplexing :

The rule usable to define the number of leds that you can drive with a number of pins :

(nbpin x nbpin) - nbpin

With 4 pins it's possible to drive 12 leds, with 3 pins only 6 leds. We need to drive 7 leds ==> we need to use 4 pins.

Use the Attiny socket to simplify the wiring.

Attiny Pin 1 - Resistor - Line 1 (blue)

Attiny Pin 2 - Resistor - Line 2 (green)

Attiny Pin 3 - Resistor - Line 3 (red)

Attiny Pin 4 - Resistor - Line 4 (black)

in a second time wire the button battery.

Attiny gnd - button battery (-)

Attiny Pin + - tilt sensor - button battery (+)

I use the tilt sensor as an interruptor.

Step 2: Programming the Dice

Compile and Upload the sketch

If it's your first time with Attiny 85, follow this link : http://highlowtech.org/?p=1695

Load the Attiny 85 sketch (i use a arduino as a ISP).

upgrade speed clock at 8 MHz.

Understand the sketch

2 libraries :

Entropy : used for random and replace the wrong standard random function.
EEPROM : used to write in Attiny and perform the randomseed number after each switch off.

2 two dimensions arrays :

tabled [7][4] : used to map led and pins
dede [8][7] : used to group led for representing the dice number.

functions

afficheled(int numled,int temps) : Display one led (numled) for a delimited time (temps)
affichede(int n ,int temps) : Display the dice number (n) for a delimited time (temps)
Lancedes() : dice generation. this function show several number before the final one.

Download the full sketch !

Step 3: Build the Dice

You need to protect the button battery place against the resin, i use playdoh.
When you mix the resin with hardener, wait until the air bubbles disappear.

One complete week for drying the dice.