Rotates the egg. Nothing more to it.

BOM

• printed parts
• M5 threaded rod and 8x M5 nuts
• M3x50 bolt and 1x M3 nut for egg holder
• 2x M3 nut and 2x M3x5 bolt
• a spring for the egg holder "idler"
• 28BYJ-48 stepper
• Arduino
• ULN2003 driver, easily found on eBay

Reused code from http://forum.arduino.cc/index.php?topic=85335.0 to drive the stepper at a constant (slow) speed. The code from the first post will work just fine, all you need to modify is the main loop().

void loop() {    motorSpeed = 1;  // set a constant slow speed    clockwise();          // start clockwise rotation }

Connect the signal and power wires from the ULN2003 driver board as follows to the Arduino Uno:

IN1 to Arduino pin 8 IN2 to Arduino pin 9 IN3 to Arduino pin 10 IN4 to Arduino pin 11

5V+ to Arduino Uno 5V 5V- to Arduino Uno GND

It will work on a Micro or Nano as well, but you'll need an external 5V power supply for the stepper.

Happy painting :)