The LED banner is an active RGB LED display, consisting of 8 rows of 80 pixels each fixed on a flexible banner. A Raspberry Pi drives it.
The following can be displayed:
- scrolling fixed images
- scrolling text in various colours
- animated GIFs
The use of a flexible banner makes it easy to transport and easy to put up.
The hardware consists of the following parts:
A Raspberry Pi is used because it can be controlled over the network, can run perl scripts and has a fast SPI port to drive the LEDs.
The power supply has been chosen to supply sufficient current for the LEDs. When the space is closed, the Raspberry Pi stays powered from the "standby 5V" output, while the LEDs are powered down.
The display consists of 8 pieces of LED strip of 80 LEDs each. They are arranged in a left-to-right zig-zag manner for ease of connecting them in series.
The LED strip consists of pairs of RGB LEDs, where each pair is controlled by an LPD8806. See  for more information on driving these chips.
The banner itself is custom made, with metal eyelets in each corner for fixation.
The software runs on the Pi and is mostly written in Perl.
To drive the LEDs, a display server written in C does the low-level driving of the LEDs over the SPI port. It also controls the white balance and takes care of gamma correction.
A simple SDL simulator of the display server has been written, that can be run stand-alone on a PC to preview led banner animations, effects, etc. The code can be found in the 'sim' subdirectory of the ledbanner repo.