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project overview
Zur deutschsprachigen Version dieser Seite
Year 2005
Number of pixels 201 (31 independent)
Grayscales / Colors
Power input 18 V AC / 4.5 A
Contact person Arne Rossius
Project website
Zur deutschsprachigen Version dieser Seite

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Mgc thumb.jpg

The MegaClock is a huge clock made from 201 x-mas light string bulbs which are arranged as four 7 segment displays. An Atmel AVR microcontroller is used to control it all, it also contains a DCF receiver to get the time and date. In addition, an infrared remote receiver is used to interact with the clock (set the alarm times etc.). The biggest problem was to find suitable transformers that didn't cost too much, but luckily, Pollin offered transformers that could source 2.2A at 18V very cheaply just in time, so I used two of those.


  • 201 x-mas light string bulbs (2.4V, 170mA)
  • Display: 4x seven-segment (7 lamps per segment), colon (2 bulbs), hyphen (3 bulbs)
  • Controlled by one shift register per display and transistors (BC337-40)
  • The colon and the hyphen are connected through resistors
  • Power supply: 2 transformers (18V~/2.2A each) and 2 rectifiers for the lamps (split to the left and right display half), 5V voltage regulator connected to one of the transformers for the circuitry
  • wooden case (size: 95 x 28 x 7.5 cm)
  • functions:
    • Time display [works]
    • Date display [planned]
    • Alarm clock with 2 alarm times [planned]
    • Countdown (can be set to Days/Hours/Minutes/Seconds) to an adjustable date/time [planned]
    • Date/time received via DCF77 [works]
    • controllable via infrared remote [planned]


  • Main Circuit contains everything except the displays
  • Display Circuit for one digit (the two lamps for the colon and the three lamps forming the hyphen are connected to the open transistors through appropriate resistors)



Finished Clock

⇒ all MegaClock photos