This is a completely silent motorized desk clock using an Arduino Nano and a CNC Shield V4 with a TMC2208 and a stepper motor. The gears are exposed and the sweep second provides a great look. The overall size of 9.5" (240mm) high by 9.1" (230mm) wide with a 6.15" (156mm) dial. A precision real time clock serves as a reference timer with an accuracy of about a minute per year. 

A video of the clock in action can be found at https://youtu.be/UFyCKlxqVp0

An updated driver circuit was uploaded in January 2023 that is even quieter and can be built using easier to find components. A video showing this improved motor drive circuit is at https://youtu.be/PR4PXR7RXEY

The primary non-printed components are:

     Ardiuno Nano
     CNC Shield V4
     TMC2208 stepper motor driver
     DS3231 precision real time clock
     Any NEMA17 stepper motor (2-3 ohm coils are preferred)
     1/16" or 1.5mm music wire
     6x3/4" or M3.5x20mm flat head wood screws
     M3x10mm screws

All of the parts are available on Amazon or other standard sources.

The advantages of the new driver circuit are:

     Quieter
     More accurate
     Uses easy to find parts
     Uses a common stepper motor
     Calibrates automatically

The old driver circuit that supports 30-35 ohm stepper motors is still available on Etsy, although your clock will be significantly quieter using the newer CNC Shield V4 driver. The old custom motor driver will still be available on Etsy https://www.etsy.com/listing/1063320628 at a discounted price until my remaining stock is gone.

Go to https://www.stevesclocks.com/sp6 to download the latest assembly guide, the Arduino Nano algorithm, or the addendum describing the CNC Shield V4 driver module.

Use the forum at https://www.stevesclocks.com/forum to discuss clock making topics or assembly issues. There is a sub-forum set up specifically for electric clocks.

The design can be printed on any printer with a 170x160mm bed size. Total print time is just over 40 hours and about 0.5kg of filament.

06-Sep-21 Update: Added a file  called simple_motor_circuit_SP6_2021_Sep.pdf that describes a method of building the motor control circuit without using the kit on Etsy. You only need to source a few common value resistors and print the new file holddown_clip.stl. These files may take a few days to be added to the zip file, but you can download them individually under "object parts".

07-Sep-21 Update: Refreshed base_back_power.stl, base_side_power.stl, frame_back.stl, and frame_front.stl with slightly better fitting pegs where the frame inserts into the base.
Also added frame_full_back_power.step and frame_split_side_power.step for users that may want to experiment with different motors or dials.
frame_full_back_power.step includes the one-piece frames and the base with power in the back. 
frame_split_side_power.step includes the segmented frame and the base with power on the side.

05-Jan-23 Update: A major improvement was added to support the new CNC Shield V4 stepper motor driver module. The clock runs significantly quieter with this change. A new base was added along with just a few updated components. Most of the top portion of the clock is unchanged.