One of the first Z80 cpu based projects that I built was a device for displaying text in mid air. The theory behind this device is that when "Magic wand" of the device is waved, user programable messages appear in mid air. This is achieved through the correct sequencing of data sent to a colomn of seven LED's, and through persistance of vision.
Technical info....
The device uses a custom built single board computer, using a Z80 cpu clocked at 2.5MHz. .... Device firmware is held within a 27c128 16K x 8 bit eprom, as well as machine code program, the eprom also holds character table maps for data to send to LED's, preset message data, and printable data tables, for information to display on LCD display.
System ram is 8K x 8 Dallas semiconductors Non-Volatile timekeeping ram.
I/O consists of a 2 line by 16 character alphanumeric LCD display, and, 1 x 8255A parrallel I/O IC. The 8255A is used to read the user switches, the position sensing mercury switch,and drives a ULN2803A octal darlington driver buffer, to drive the "wand" LED's. |
