Summary update 2(2016/11/25) added printable spacers and a motor mount plate for 20mm npm motor update 1(2015/2/6) : added assembly sequence sheet . this is a simple clock based on a single geared stepper motor which i found in surplus 10 for a dollar... The motor is basically a 1:30 geared motor working at 12v with a 3mm shaft. The single motor is driven by a attiny2313 and l293dd circuit with the coded written in arduino ide. The single motor moves a gear train which in turn moves the minute ring and hour ring. The attiny pulses the motor every minute to move the minute wheel and the hour wheel. buy at: https://www.tindie.com/products/ekaggrat/holo-clock-2/ https://www.youtube.com/watch?v=1EtiEFQ4Aqg Instructions print all the parts at minimum 0.2mm layer height bolts : m3 x 45mm 4 m3 x 25 mm 2 m3 x 22 mm 1 m3 x 10 grub screw for motor gear m3 nut x 7 for npm motor (optional) m2 x 10 2 m2 nuts 2 for bj25 / bj20 motor m3 x 15 self tapping screws 2 pcb spacers / cut from any brass/copper tubing ( printable option also ) 4.5 outer dia x 3.5 mm inner dia x 12.mm length 2 pieces 4.5 outer dia x 3.5 mm inner dia x 8.5.mm length 4 pieces 4.5 outer dia x 3.5 mm inner dia x 6.5.mm length 2 pieces for the stepper you can use any 20mm or 25mm diameter geared more than 1:10 ratio, bipolar or unipolar.