Updated March 1, 2001: added schematic and Eagle files.
This latest member of Wise Clock family has two major improvements over its predecessor:
- the real time clock is upgraded to one of the best RTC chips available, the extremely accurate (±1 minute per year), temperature compensated, DS3231 from Maxim (also used in Chronodot);
- the LED display, from Sure Electronics, is bigger (32x16 pixels) and better (red, green and yellow pixels).
The main board, shown below, also features:
- ATmega644P microcontroller running at 16MHz, with the Arduino/Sanguino bootloader;
- SD card socket;
- piezoelectric buzzer;
- three function buttons and one reset button;
- battery backup for the real time clock (it keeps the time even when the board is not powered);
- headers that plug directly into the 2x8 connectors in the back of the display, so that a ribbon cable is not required;
- a small prototyping area, to extend clock's functionality (e.g. adding infrared remote control, FM radio, dimming on the ambient light etc);
- ICSP 6-pin header;
- power through USB miniB connector;
- 6-pin FTDI connector, compatible with the FTDI cable and the FTDI breakout;
- all 4 ports of the microcontroller (32 pins) are accessible to a "shield"-like expansion board;
- ability to cascade a second 3216 display through 2x8 pin header (plus ribbon cable);
- blue power LED.
A few design considerations:
- the main board fits perfectly within the dimensions of the LED display;
- the function buttons are accessible from the top, as is the SD card;
- power connector (USB miniB) accessible from a side;
- FTDI header placed at the bottom of the board (does not take lateral space);
- between the main board and the display board there is room left for air circulation, in case the display chips get warm;
- buzzer placed close to the edge of the board;
- enclosure made of two laser-cut plexiglass plates, sandwiches the two boards (main and display) together, held in place with a few screwed standoffs.
The software for Wise Clock 3 is being adapted and expanded from Wise Clock 2, with the addition of new features (Pong clock, temperature display etc). The HT1632 files (h and cpp) for the new 3216 LED display are already tested and proven (see this Arduino forum thread).
As always, I will keep you posted. Stay tuned.
Eagle files can be downloaded from here: schematic, board layout.
The schematic is also shown in the image below.