This is a nearly silent motorized desk clock using an Arduino Nano and a custom drive circuit controlling 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. Accuracy can be tuned to less than a second per day.
A video of the clock in action can be found at https://youtu.be/UFyCKlxqVp0
The primary non-printed components are:
mini USB cable
NEMA17 stepper motor with 30-35 ohm coils
custom motor driver available on Etsy
1/16" or 1.5mm music wire
6x3/4" or M3.5x20mm flat head wood screws
The custom motor driver is available for US$8 on Etsy at https://www.etsy.com/listing/1063320628 Free shipping is included within the US. International orders are forced to ship through customs with high postage costs, so I will add an extra kit to each order to help offset some of the cost. The controller can also be built without using the circuit board by directly soldering the resistors to the Arduino Nano.
Go to https://www.stevesclocks.com/sp6 to download the latest assembly guide, the Arduino Nano algorithm, or notes on building the controller without using the circuit board.
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.