Hollow Clock

Witness the dance of machinery and light. This is more than just a clock it's a miniature precision mechanical theater for your desktop. We've abandoned boring chip-based timekeeping using an **Arduino to drive a 28BYJ-48 stepper motor** to move the hands with real mechanical transmission; innovatively incorporating a **magnet Hall sensor positioning system** which automatically "resets to zero" on every startup achieving long-term timing accuracy comparable to a quartz clock. The casing features an **extreme hollowed-out design** when the built-in LEDs illuminate the outlines of the hands and numbers are projected onto the wall as floating shadows creating a unique immersive time-reading experience. From printing assembly wiring to debugging this project will guide you through a complete mechatronics creation journey.

Core Highlights

• 🎯 Magnetic control zeroing never goes astray: Unique "physical calibration" solution. The pointer shaft and casing are equipped with **neodymium magnets and Hall sensors** respectively. Each time power is applied or at scheduled intervals the pointer automatically rotates to find the magnetic attraction point precisely resetting to 12 o'clock completely eliminating cumulative errors from stepper motor step loss. This is the core of this design's precision and reliability.
• ⚙️ Real mechanics visible transmission: Through the side cutouts you can glimpse the operation of the **stepper motor and gear train (or worm drive)**. Time flows in a tangible mechanical way giving warmth and life to cold digits.
• 🌌 Floating light and shadow dual display: It's both a physical pointer clock and an ambient light and shadow device. When the background LEDs are turned on time "migrates" from the physical object to the wall creating a cool floating projection and fostering a tranquil or tech-savvy spatial atmosphere.
• 🔧 Full-stack open source deeply controllable: Provides **complete 3D models Arduino source code detailed BOM list and wiring diagrams**. You can adjust gear ratios to change speed modify code to customize light and shadow modes or even add network time synchronization. This is a perfect platform for you to learn and modify.
  
  Bill of Materials (BOM)
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• Category	Item	Specs/Quantity	Description
  Control Core	Arduino Nano	5V with header pins ×1	Main Controller
  Power System	28BYJ-48 Stepper Motor + ULN2003 Driver Board	5V kit ×1	**Do not buy 12V motor**
  Positioning System	Neodymium Magnets 8mm×3mm	×3	For pointer shaft and casing positioning
  	Hall Sensor (e.g. A3144)	×1	Detects magnet for zeroing
  Optical System	WS2812B LED Strip	20-30 LEDs	Creates floating light and shadow
  	Resistor 220Ω, Capacitor 1000µF	Each ×1	Signal and power filtering
  Structural Parts	3D Printed Parts	Full set of casing and gears	Approx 200g PLA
  Connectors	Self-tapping screws M2×5mm/M2×10mm	Several	Securing structure
  	Dupont Wires Thin Wires	A batch	Wiring and soldering
  Power Supply	USB 5V/2A Quality Power Supply	×1	Stable power supply to avoid flickering

  
  Core Wiring Diagram

• Motor Drive:
  • Arduino (D2, D3, D4, D5)→ ULN2003 (IN1, IN2, IN3, IN4)
  • Arduino (5V, GND)→ ULN2003 (VCC, GND) (Common Ground!)
  • External 5V Power +→ ULN2003 (+)
  • External 5V Power -→ ULN2003 (-) (Common Ground with Arduino GND!)
• Magnetic Zeroing:
  • Hall Sensor VCC→ Arduino 5V
  • Hall Sensor GND→ Arduino GND

  • Hall Sensor OUT→ Arduino D6 (customizable)
    
     

    

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    Project AddressOriginal model by shiura you can view the project here:https://www.instructables.com/Hollow-Clock-4/