Current Projects:
Pinball Project
CNC Router
PIC Computer
LED Sign 2003

SigArch Sign Version 3

In the tradition of former SigArch sign projects, we designed yet another LED dot matrix display. This version includes built-in character generation and is reprogrammable via an RS-232 serial port.

Unlike earlier monolithic sign designs, we opted for a modular approach which would allow us to expand the sign horizontally to an arbitrary length, limited only by power requirements. The finished sign has a small (2 by 2") controller board and three dual 5x7 LED matrix display driver boards (3 by 2"). The controller board has a MAX233, a 12MHz TTL oscillator, and a PIC18F252, while the driver boards each have seven TIP30C PNP transistors, two 74LS164 shift registers, and ten 2N3904 NPN transistors. Schematics are shown below:

Schematics

All resistors are 1K unless otherwise noted. The driver boards also have 0.1uF capacitors, and the control board has a 100uF and a 0.1uF capacitor. The oscillator on the control board is 12MHz in our circuit, but other values will work.

LED Matrix Driver
PIC Control Board

Codepwd

The PIC18F252 code is separated into 3 files:

Main program
Font data
Example strings