This project is 6″ seven-segment.All segments consist of fourteen 5mm super bright LEDs except dot segment it use only 4 LEDs.I design this project use for multipurpose such as big 7-segemnt display ,big digital clock,digital timer etc.The project designed as a module for one digit .You can cascade up to 8 module or 8 digits. For each digit there are two options on PCB which you can use or ignore these options for each digit PCB.
– 3 switches on PCB.
– 1 Opto-isolate input.
PIC16F876A to be used to control all of task on this project.You can replace with any 28 pin PIC microcontroller.PortB set as output to drive all segments.PortC set as output to drive each digit vai ULN2803 which is octal hight voltage ,high current darington transistor array.
Jumper 1(J1) on PCB used to determine digit itself module(digit1 – digit8).
The solder pad at the bottom of PCB use for cascade the digit. It include with all segments of a,b,c,d,e,f,g,h,dot(p) and digit1- digit 8.To cascade the digit you just solder the PCB pad then select the J1 to determine the digit itself. If the digit place away for each digit you can use coper wire or flat cable instead as show in the below picture.
Show solder pad for cascade
click to enlarge
How to cascade the digit
The example firmware included in this project is 4 digits counter writen for CCS C compiler.You can modify the source code if you want more than 4 digits. To use with this example firmware you must assembly 1 complete PCBs (all components installed) and the rest of 3 PCBs you need to solder all LEDs only.Then determine the complete PCB to be digit 1 by jumper 1 and the rest of 3 PCBs determine to be digit 2, 3 and 4 respectively.
PCB and schematic
include bottom,over lay,composite
4 digits counter example firmware
This example writen for CCS compiler