3D Printed Clock With Perpetual Calendar

Clock with Perpetual Calendar

Perpetual calendar is one of the representative mechanism of complication clocks and watches. It shows correct date up to 2099 without correction because it can handle all kind of month lengths including February of leap years.

Features

• Mechanical perpetual calendar which is only seen on very expensive watches and clocks
• This clock has four sub-dials to show 24hours, month, date and day of the week
• Ready for practical use. The clock itself is driven electrically and more accurate than mechanical one. No winding necessary
• Easy calendar adjustment by direct manipulation of hands

Design highlights

• Four sub dials are arranged regularly
• All six hands rotate CW
• Skeleton design to maximize the visibility of the mechanism
• No bearings or metal shafts are used but works smoothly
• No screw heads in front
• You do not need supports in 3D print
• Printable with relatively smaller printers including Prusa MINI (size of maximum part is 180 x 180mm)

Note Feb 26, 2023:

The calendar proceeds to the next day around 10:30-11:00 at night. You can see the motion at that time, however, it might be confusing at midnight. To avoid this problem, attach the main cam at the bottom ("24h-gear.stl") rotated 90 degrees CCW. In this case, the calendar changes at around 4:30-5:00 in early morning.

You can also use modified version of "24h-gear.stl" to tune the timing of the calendar change with 2hours step. ("24h-gear-2h-behind.stl" and "24h-gear-4h-behind.stl")

Necessary parts

• 28BYJ-48 geared stepper motor and driver circuit comes with
• Arduino nano or other micro controller
• One tactile switch
• 2mm tapping screws of various lengths
• Thin rubber bands
• Lubricants (silicone grease)
• Double sided adhesive tape

Please take a look at the "Assembly Guide" video below at step 1.

• If the size of build table of your printer is smaller than 250 x 250mm, use "square-backplate-for-small-printer.stl" (180 x 180mm) instead of "circular-backplate.stl" (250 x 250mm).
• Print parts with supplied posture. No supports needed.

You can select modified version of "24h-gear.stl" to tune the timing of the calendar change with 2hours step. ("24h-gear-2h-behind.stl" and "24h-gear-4h-behind.stl" instead)

Please take a look at the assembly guide video.

Front frame holds all hands and several gears.

• Please make sure that all axes rotate smoothly before assembly.
• Remove debris and blobs from the parts well for smooth rotation.
• Adjust the strength of the rubber bands. The main arm (green part) should be smoothly returned by the tension of the stronger rubber band.

Rear board holds several idler gears, click hooks and a stepper motor.

Engage front and rear assemblies.

• Watch here and there to engage them without interfering parts. Especially, click hooks and main arm tend to block them.
• It is better to engage them with the program wheel at the position of February (at deepest channel)
• Adjust positions (phase) of the month gear and program wheel.
• Adjust positions (phase) of 12 and 24 hours.

Confirm the smoothness of the motion of the all parts without motor.

Then attach the stepper motor with two tapping screws.

You can select two types of month sub-dials. One has DEC at top, and the other is JAN.

• Print the sub dials with the function of "pause at height" to change the material during print. Change the material at height=1.5mm.
• Stick sub dials to the front frame with double sided adhesive tape.

Test the clock with "stepper-test.ino" which rotates the minute hand as fast as possible.

Then flash "clock.ino" to use it as an usual clock.

Operation

• To adjust the time, press the tactile switch. The clock runs fast.
• To adjust the date, rotate the date hand or the corresponding gear.
• You can advance the date by pulling up the left end of the main arm (green part).
• To adjust the month, pull up the main arm to disengage the hook to the program wheel, then rotate the program wheel. Note that the program wheel rotates CCW. "L" letter means leap year.
• To adjust the day of the week, just rotate the week hand.

Use optional parts (hanger.stl and driver-holder.stl) to fix the circuitry and hang the clock to the wall.