Fairy Lights and other Hardware
The hardware...
The firefly hardware is highly hierarchical, so there are 3 levels of
embedded processors before any information even reaches a PC. These levels
include the fairy light itself, the control board, and the serial board. There
are up to 80 fairy lights for every control board, and up to 10 control
boards for each serial board. A PC can control approximately 8
serial boards, although that doesn't preclude a network of PCs furthering
the hierarchy and controlling a larger number of lights.
Fairy Lights
Each fairy light consists of a bright white LED (this can be changed for a
colour one, although we haven't tried that in detail yet), a PIC628 surface
mount processor, a capacitor and a diode. They can be powered from a 5V DC
supply with no need for any separate addressing wire as communications are
made over the 5V power line.
When built each of these fairy lights is identical, carrying exactly the
same program on the chip, and therefore exactly the same address by which the
control board can refer to it.
Control Boards and Serial Boards
Control boards and serial boards are both connected via a bus of UTP patch
cables. These UTP cables carry a 36V DC power supply, which on the control
boards is then stepped down to 5V for use on the fairy lights themselves.
Serial boards have no need to provide connectors for the lights directly, but
instead use a HIN232 chip to interpret serial communications from the PC. It
is anticipated that future versions of this board will make use of USB.
