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](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 :)

Post-Printing

The tolerances are pretty tight. The M3 nuts and the stepper shaft are most easily inserted after heating them slightly with a heat gun or soldering iron.