MegaClockEnglish

project overview

Year	2005
Number of pixels	201 (31 independent)
Grayscales / Colors	2
Illuminant	christmas light string bulbs
Power input	18 V AC / 4.5 A
Contact person	Arne Rossius
Project website

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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.

Specifications

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]

Schematics

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)