Saturday, July 2, 2011

Introducing C3Jr kit

Although I posted about ClockTHREE Junior (aka C3Jr) here, this is its formal introduction in my blog.

C3Jr is an Arduino-compatible, open-source alarm "word clock", which displays the time in words, similar to the original QlockTWO(*). It is the result of numerous hours of electronic design, mechanical engineering and programming by the Wyolum team. The goal of this effort was to develop a kit that would be affordable, easy to assemble and stand out aesthetically.

The content of the C3Jr kit is shown below (click for a larger picture).

It includes all the electronic components and mechanical parts to build the C3Jr clock shown in the next photo (on Justin's workbench).

The large display is based on a matrix of 16x8, individually addressable, white (or blue) LEDs. Beside lighting up small letters (one letter per LED) that make up words, the display can also be seen as a matrix of 16x8 pixels, which can show scrolling characters or animated sprites.

The time-keeping chip is the extremely accurate (max 2 minutes deviation per year), temperature-compensated, DS3231, with a 3V coin cell for backup (keeps the time when clock is not powered).

Here is a list of the parts:
  • large (18cm x 23cm) PCB;
  • ATmega328 with 28-pin socket;
  • either 16MHz resonator or 16MHz crystal + two 22pF capacitors;
  • 74LS154 and 24-pin socket;
  • STP08DP05 and socket;
  • DS3231, pre-soldered to the board;
  • CR2032 (3V) coin battery and battery holder;
  • 130 diffused white (or blue, on request) 5mm LEDs;
  • 17 PNP transistors 2N5401;
  • 4 decoupling capacitors 100nF;
  • 100uF electrolitic capacitor;
  • 17 resistors 100 ohms;
  • 6 resistors 10K;
  • 2 resistors 4K7;
  • 2 resistors 1K;
  • 2 resistors 680 ohms;
  • USB type B (power) connector;
  • speaker/buzzer;
  • 6-pin right-angle male header used as FTDI connector;
  • 4 right-angle push buttons;
  • 5k potentiometer;
  • set of laser-cut, black plastic, baffles;
  • laser-cut acrylic faceplate with your favorite choice of font;
  • laser-cut plastic backplate;
  • set of standoffs, screws, nuts, washers.
The C3Jr kit is available for order here or in my store.
Here are the assembling instructions.

The schematic and board layout for C3Jr are shown in the images below (click on the image for the bigger version). The KiCAD files are available for download here.

(*) QlockTWO is an industrial product (as opposed to the amateur, home-made, C3Jr). Take a look at how it is manufactured.

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