Digital Crazy Hours and Minutes - WiFi Sync Clock

Introducing a mechanical digital clock with numbers strangely arranged.

Technical highlights

• Usually, intermittent motion mechanism such as Geneva drive is necessary to decrease the number of the motors of mechanical digital clock. Contrary, this clock has a constant mesh (permanently engaged reduction gear) between tens and ones places of minute numbers. The ratio of the reduction gear is coprime (7 : 10) and 70 numbers can be shown by one motor.
• The order of the numbers are not random but optimized to minimize the time to update. Average angle of rotation of the central rotor is less than 360 degrees.
• To show the current time correctly when it is powered on, not only the WiFi connection capability but also origin finding mechanism are necessary. This clock has an one-way rotation blocking mechanism. The rotors for minutes are stopped at 00 when it moves backward, but pass through there when rotating forward.
• Herringbone gears are used to hold the rotors without central axes.

Note : This model needs large (30x30cm) 3D printer to make.

Supplies

• two 28BYJ-48 stepper motors and driver board (around 2USD each)
• one M5Stamp-C3 micro controller with WiFi (5.90 - 6 USD)
• cables for pin headers
• M2 tapping screws with various lengths
• short M3 tapping screws (used to attach the stepper motor)
• lubricant (silicone oil or grease)

Step 1: Print Parts

• Print parts with supplied posture.
• No supports needed.
• Print 8 copies of "holding-gear-8copies.stl" and "gear-fix-8copies.stl".
• Remove debris and blobs from the printed parts well.

Step 2: Attach the Hook (origin Mechanism)

• Stick a small nut to hook as a weight.
• Attach the hook to the frame using "hook-pin.stl" and "hook-guide.stl".
• Please make sure that the hook moves smoothly.

Step 3: Assemble the Rotors

• Place the 1min and 10min rotors upside down.
• Align two 0s.
• Place the gears on the odd numbers. At No.5, use "idler-gear.stl" (gear without axis)
• Attach the frame upside down. Please take a look at the video clip above.
• Confirm the smooth rotation and one-way origin lock mechanism.
• Attach the gear-fix discs to the gears.
• The hour rotor can be assembled in the same way.

Step 4: Attach the Electronic Circuits

• Attach two stepper motors and driver boards using tapping screws. Use short M3 screws to attach the stepper motor, otherwise M2 screws are adequate.
• Connect micro controller and motor drivers using pin header cables.

Step 5: Rear Cover

• Fix the M5Stamp C3 micro controller to the rear cover using retainer. No screws needed.
• Attach the rear cover to the frame. Use 6 M2 screws with adequate length.
• Hang the clock on a wall. Since the origin mechanism relies on the gravity, it should be upright.

Step 6: Flash the Program

• Flash the code "clock.ino" to the M5Stamp C3 using Arduino IDE.
• To perform the test, turn on the flag named `DEMO_MODE` at line #4, as

#define DEMO_MODE true

• Turn off (set to false) the flag above, to acquire current time via WiFi. Set SSID and password in the source code or use SmartConfig feature of ESP32.
• If the motion is not smooth, use lubricants.